Drug delivery from a solid formulation during breastfeeding-A feasibility study with mothers and infants.

BACKGROUND: Breastfeeding is critical to health outcomes, particularly in low-resource settings where there is little access to clean water. For infants in their first twelve months of life, the delivery of medications is challenging, and use of oral syringes to deliver liquid formulations can pose both practical and emotional challenges.
OBJECTIVE: To explore the potential to deliver medicine to infants via a solid formulation during breastfeeding.
METHODS: Single center feasibility study within a tertiary level neonatal unit in the UK, involving twenty-six breastfeeding mother-infant dyads. A solid formulation of Vitamin B12 was delivered to infants during breastfeeding. Outcomes included the quantitative change in serum vitamin B12 and assessment of maternal expectations and experiences.
RESULTS: Delivery of Vitamin B12 through a solid formulation that dissolved in human milk did not impair breastfeeding, and Vitamin B12 levels rose in all infants from a mean baseline (range) 533 pg/mL (236-925 pg/mL) to 1871 pg/mL (610-4981 pg/mL) at 6-8 hours post-delivery. Mothers described the surprising ease of 'drug' delivery, with 85% reporting a preference over the use of syringes.
CONCLUSIONS: Solid drug formulations can be delivered during breastfeeding and were preferred by mothers over the delivery of liquid formulations via a syringe.

Introduction

Breastfeeding saves lives, improves health and cuts health costs worldwide. In low-resource settings the delivery of medications, such as de-worming and retrovirals as well as nutrient and mineral supplementation, in liquid formulations is challenging, as liquids need to be refrigerated for storage, and syringes require clean water for sterilization [1]. However recent studies have also highlighted the emotional and practical challenges for many parents, of treating infants with liquid formulations as many infants demonstrate aversive behavior towards drug delivery from oral syringes [2]. The potential alternative of solid formulation drug delivery during breastfeeding was previously shown during in-vitro (lab-based) studies using a breastfeeding simulation apparatus [3, 4]. Now, this study aimed to evaluate the feasibility and acceptability of solid formulation delivery in a clinical setting with recruited infants while breastfeeding. It is the first clinical feasibility study of solid formulation delivery during breastfeeding to be undertaken with mother-infant dyads. Vitamin B12 was chosen as a therapeutic, due to its physiological importance for infant development, and its known safety profile over a wide dosage range [5]. It served as a model compound for other possible therapeutic formulations.

Methods

Study design

This was a single center feasibility study, at the University of Cambridge Addenbrooke’s Hospital Trust (study start date: 9 July 2018, study end date: 31 December 2018). Vitamin B12 was given during breastfeeding via a nipple shield during a single breastfeed. A qualified nurse or lactation consultant known to the mother was available for breastfeeding support and advised on the appropriate application of the nipple shield to the breast. Assessments included quantitative measurements of serum vitamin B12 levels at baseline and 6–8 hours after the interventional breastfeed, and a mixed methods assessment of maternal expectations, experience, and acceptability. The interviewer was a female researcher trained in line with the institution’s guidelines for clinical research. Interviews were led by a single interviewer for consistency. Primary outcome measure was the detection of the change in vitamin B12 concentration in the infants’ blood 6–8 hours after delivery from a nipple shield during breastfeeding. Secondary outcome measures was the qualitative assessment of impact on maternal expectation, experience and acceptability.

Study population and participant recruitment

Breastfeeding mother-infant dyads were recruited through convenience sampling from the neonatal unit and postnatal transitional care wards: Potentially eligible mother-infant dyads were identified by the clinical team, following which mothers were approached by the research team. Eligibility included infants with a corrected age of <12 months, clinically well and assessed by the lactation team to be competent at breastfeeding. Exclusion criteria were hypersensitivity to the vitamin B12 tablet’s ingredients, short bowel syndrome, and malabsorption. No restrictions related to prior B12 supplementation or potential interactions with human milk were considered, as the study was solely designed as a proof-of-principle. The total number of participants was based on guidelines for feasibility studies, and qualitative research, and in alignment with the objective of reaching information saturation as well as a power calculation for changes in B12 levels [6, 7].

Nipple shield and vitamin formulation

Commercial ultrathin contact nipple shields (Medela, UK) of 16 mm (size S), 20 mm (size M), or 24 mm (size L) size, as recommended by the lactation support team, and following evidence from an earlier scoping exercise with mothers [1], were selected and worn by mothers during the study feed. These nipple shields are commonly used on the hospital’s maternal and neonatal wards, made from transparent BPA- and taste-free soft silicone. A sublingual vitamin B12 tablet (1000 μg Methylcobalamin, JustVitamins Ltd, UK), suitable for vegans and without known allergenic components, was placed into the shield’s teat immediately prior to the feed, and the mother then breastfed as usual.

The tablet characteristics comprised the following: round tablet with a diameter of 8 mm and an average weight of 0.26 g; ingredients: Sorbitol, Stearic Acid, Beetroot, Blackcurrant, Magnesium Stearate, Methylcobalamin. To investigate the vitamin B12 tablets’ disintegration properties, lab-based studies were performed. Hereby, the vitamin B12 tablets were placed in the silicone teat of a 20 mm Medela ultrathin contact nipple shield, and delivery into full-fat cow’s milk investigated in triplicate using a breastfeeding simulation apparatus, capable of simulating both the process of lactation and infant feeding by mimicking the average flow rates/patterns of milk during breastfeeding and the infant’s suckling pressure at physiological relevant conditions. The percentage of tablet released within 5, 10 and 20 min was approximately 41%, 62%, and 74% respectively, and no tablet break-offs during disintegration or dislocation of the remaining tablet through the silicone teat’s three holes following the experiment was observed.

Vitamin B12 levels

A baseline blood sample (venous blood or heal brick) was taken within a week prior to the study feed and a peak level at 6–8 hours after the study feed. The timing for collection was based on the pharmacokinetic profile and anticipated peak B12 levels [8]. Samples were immediately centrifuged and separated, with serum stored at -20°C for later batch analysis. Serum vitamin B12 levels were analyzed using a LOCI vitamin B12 assay (Siemens Healthcare) at the Core Biochemical Assay Laboratory (CBAL), Cambridge University Hospitals.

Mixed methods approach

A combination of tablet-based Likert-scale questionnaires and recorded semi-structured interviews, developed based on established guidelines [9], were undertaken before and after the study feed. Interviews were performed in a quiet area at the infants’ cot side to avoid separation of mother and infants. Discussions focused on the evaluation of maternal expectation, experience, and acceptability of the intervention. Interviews were voice-recorded, but to support honest critical reporting, mothers also provided scored answers on a tablet device. Data on those scores was quantitatively evaluated, while semi-structured interviews were transcribed verbatim, and potentially identifiable data anonymized. Analysis was facilitated by ATLAS.ti (Scientific Software Development GmbH), using an inductive approach of thematic content analysis [10, 11]. Hereby, an initial coding framework emerged following pre-reading, a line-by-line open-coding approach, and regrouping steps. A final coding framework was developed, through iterative revisions within the research team.

Statistical analyses and power calculation

The sample size was based on the literature for preterm infants’ supplementation, in which B12 between 8–12 weeks led to an approximate three-fold rise in serum B12 levels. As such this sample size would provide 90% power at the 5% level to demonstrate a two-fold increase in B12 [12-14] (two sided superiority). All data shown is presented as mean percentage or mean with standard deviations and ranges if normally distributed. Differences in serum B12 levels before and after the test-feed were assessed using paired student t-test. Exploratory analyses were undertaken in relation to impact of gestational age at birth and postnatal age on increases in vitamin B12 levels post the test feed. Analyses was undertaken using SPSS 26 and p<0.05 was considered statistically significant.

Ethics approval

The study was approved by the London, Brighton & Sussex Research Ethics Committee (18/LO/0551). All participants provided their written informed consent to take part and to be quoted anonymously in this publication. ClinicalTrials.gov Identifier: NCT03799367.

https://clinicaltrials.gov/ct2/show/NCT03799367. The study was registered and released on 8 July 2018, prior to the start of patient recruitment. It was released to the public following review by the PRS protocol team on 10 January 2019. The authors confirm that there are currently no ongoing and related trials for this drug/intervention and that all existing ones were registered. Mother-infant dyads were recruited from 9 July until the end of December 2019. Following completion of the post-feed interview, enrolment in the study for a respective mother-infant dyad was completed.

Results

The study aimed to recruit a maximum of 30 mother-infant dyads. A total of 43 mothers were approached, of which 26 (60%) consented to participation and 20 completed the full study protocol (Fig 1, Table 1). Reasons for non-completion/exclusion from analysis in the six cases were: a change to bottle feeding [1], discharge before study feed [2], lack of appropriate blood sample [2], and parent withdrawal [1]. All infants who started the test feed with the B12 completed the feeding intervention.

Fig 1

Consort diagram.

Table 1

Participant characteristics (mother-infant pairs, n = 20).

Characteristics	Mean (range) or N (%)
Mothers’ characteristics
Mother’s age, mean (range) [years]	32.4 (Range 23–39)
Total number of children, N (%)
1	9 (45)
2–3	10 (50)
>3	1 (5)
Infants’ characteristics
Gestational age at birth, n (%)
Preterm <32 weeks	3 (15)
Preterm 32 to <37 weeks	4 (20)
Term > 37 (37 to <41 weeks)	13 (65)
Birth weight, mean (range) [gram]	2769 (890–4145)
Age at time of study, mean (range) [days]	16.2 (2–70)
Corrected gestational age at time of study, mean (range) [days]	-3.7 (-30-15)
Stay of infant on Neonatal Intensive Care, N (%)
Yes, up to 1 week	5 (25)
Yes, 1 week or longer	7 (35)
No	8 (40)
Exclusive breastfeeding at time of study, N (%)
Yes	7 (35)
No, also NG	9 (45)
No, also bottle	4 (20)
Use of nipple shield, N (%)
For current infant	9 (45)
Only for a previous infant	1 (5)
Never	10 (50)

Vitamin B12 delivery

The mean duration of the study feeds (n = 20) was 19.8 ± 5.5 min (Range 15–30 min). The lactation team and mothers did not report any aversive impact of the tablet’s presence in the nipple shield on the process of feeding. Complete tablet disintegrating was achieved in all study feeds, with no residue tablet visible to the naked eye. Changes in serum B12 levels are provided in Table 2. Vitamin B12 levels rose in all infants from a mean baseline (range) 533 ± 188 pg/mL (236–925 pg/mL) to 1871 ± 1228 pg/mL (610–4981 pg/mL) at 6–8 hours post-delivery.

Table 2

Changes in serum vitamin B12 levels from baseline to 6–8 hours after the study feed.

Infant ID	Gestational age at birth [weeks+days]	Age at time of study [days from birth]	Baseline serum vitamin B12 level (pre study feed) [pg/mL]	Peak serum vitamin B12 level (6–8 hours post study feed) [pg/mL]	Percentage change
1	31+5	55	575	3484	506
2	26+5	70	681	2577	278
3	37+0	6	449	1743	288
4	37+2	6	858	1285	50
5	41+1	4	303	1045	245
6	31+3	30	236	4981	2011
7	38+4	21	593	1928	225
8	34+6	19	596	4104	589
9	41+1	6	430	1006	134
10	40+6	6	925	1121	21
11	37+6	4	565	1321	134
12	41+2	6	325	610	88
13	40+2	4	660	1259	91
14	40+2	6	582	1104	90
15	41+0	8	397	866	118
16	32+1	29	352	1506	328

Vitamin B12 levels of four infants were excluded as samples clearly showed haemolysis. Pg: pictogram, mL: millilitre.

Mixed methods assessment

The mean (range) duration of the semi-structured maternal interviews to assess expectations (pre-study feed) and experiences (post study feed) were 7.7 (4.4–16.6) minutes and 7.0 (3.5–12.2) minutes, respectively.

Maternal expectations (pre-study feed)

Identified themes related to the uncertainty of risks but also curiosity for the intervention, as well as strong expectations of perceived emotional and practical benefits. Areas of concerns included the use of a nipple shield itself, and the therapeutic it contained. In particular, for mothers who had not previously used nipple shields, unknowns about the infant’s reaction and behavior during the study feed were the predominant source of concern, including the infant’s ability to latch and the alteration of normal breastfeeding behavior. “It might take some [time] getting used to. I don’t know how she is going to do with a nipple shield. I mean the way that she latches.” (M12) In contrast, mother with previous experience using nipple shields, reflected exclusively on the tablet’s disintegration properties, its potential impact on the milk’s taste and implication on breastfeeding practice. “[…] will it dissolve, and will she… be able to taste it?” (M2)“…if I was going to have a worry it would be that it would give them a negative experience of breastfeeding and then would put them off breastfeeding.” (M6) Despite associated worries, mothers described their positivity and curiosity in attempting vitamin delivery during breastfeeding. “I think it’s worth looking into. […] I think it is a good idea.” (M12) “It is just quite exciting to see how it works.” (M2)

Participants expected an emotional improvement or an increased convenience of infant therapeutic delivery whilst feeding (Table 3). This included a reduction of stress for both mother and infant, or a perceived enhancement in physical intimacy, alongside a perception of this method as being more ‘natural’ (Table 3). Suggested potential practical benefits included time saving, fewer dosing errors and being “less messy”. “It seems a more natural way of administering medication.” (M5)

Table 3

Comparison of maternal expectations before and experiences reported after the study feed.

	Likert scale before study feed	Likert scale after study feed	Change [%]
The nipple shield with a vitamin tablet…
…will be/was easier than using an oral syringe.	7.0 ± 1.6	8.3 ± 1.8	+19
…will make/ made me less worried.	7.2 ± 2.0	8.6 ± 1.5	+19
…will make/ made my baby feel less upset/ distressed.	7.7 ± 1.5	8.6 ± 1.4	+12
…will help/ helped me to feel closer to my baby.	7.7 ± 1.6	8.4 ± 1.7	+9

The Likert scale was used (10 = highly agree, 0 = highly disagree). Numerical values are shown as mean ± standard deviation. Further quotes can be found in S1 Table.

Maternal experiences of the study feed (post feed)

A positive experience was reported by the majority of mothers along with a feeling of surprise in the ease of use of the nipple shields, and the lack of impact on the infant’s breastfeeding behavior. Mothers attributed their surprise about their infants’ contentment to the lack of experience and emotional factors relating to preconceptions about nipple shields. “What is this going to feel like? And is it going to be a barrier to feeding? And is he going to latch properly.’ But actually, all of that was fine.” (M4) Practical concerns remained regarding the potential of incomplete therapeutic delivery. “What would you do—if it was an actual drug–and [you had] given only part of a dose? (M2)

Overarching themes: Perceived advantages and acceptability

Mothers emphasized the potential of this therapeutic delivery method to de-medicalize infant treatment and described it as “less invasive” (M7), and “not an aggressive method of delivery” (M16), “you are not forcing them” (M20). This appeared to relate to an emotional burden for mothers of infants with prior neonatal intensive care experience. “[…] for babies who’ve had to undergo all that, to have something so natural, is lovely.” (moved to tears) (M12) “[…] I would like something more natural for her. […] Everything that has to do with syringes and medication makes me think of NICU and, you know, this very scary part of her life.” (M19) All mothers advocated for the availability of oral infant therapeutic administration during breastfeeding, with the majority preferring this method of infant therapeutic delivery (see Table 4), emphasizing that it would provide “choices” (M8).

Table 4

Summary of reported maternal experience and acceptability of the study feed.

	Agreement [%]
Experience
The nipple shield with a vitamin tablet…
…was a positive experience	95
…was easy to use.	95
…was comfortable to wear.	95
My baby….
…latched as usual.	95
…breastfed as usual.	90
Acceptability
I prefer to give medicines/ nutrients using a nipple shield over using an oral syringe.	85
I think the nipple shield could be an acceptable method for nutrient delivery.	100
I think the nipple shield could be an acceptable method for medicine delivery.	95
I would like that medicine/ nutrient delivery during breastfeeding becomes possible for parents in the future	100

Further quotes can be found in S2 and S3 Tables.

Discussion

This is the first clinical study to show that a solid formulation can be delivered successfully to infants during breastfeeding. The study demonstrated that the formulation used was easily dispersed in human milk during a breastfeed, with all infants showing a clinically significant rise in B12 serum levels. Neither mothers themselves, nor the lactation team, reported any apparent impact of the tablet’s presence in the nipple shield on the process of feeding.

This feasibility study used B12 as a marker of utility for this novel delivery approach, not as a therapeutic option or to explore pharmacokinetic uptake in infants. However, the findings do highlight the complexities of bioavailability in the newborn not related only to breastfeeding, but also to gut pathology, postnatal age, and gestational age. Findings of this study suggest that vitamin B12 absorption was dependent on postnatal age and independent of prematurity or birth weight (total absorption: 0.0072 ± 0.0029% for infants <7 days of age, and 0.329 ± 0.0173% infants aged 19 − 70 days). Given the small sample size, no conclusive statement can be made, about the interdependency between postnatal age and vitamin B12 absorption, and further investigations would be required. The findings are however in keeping with the literature for preterm infants’ supplementation, in which B12 between 8–12 weeks led to an approximate three-fold rise in serum B12 levels [13, 14].” but the findings are in keeping with the literature on B12. Robust pharmacokinetic studies would be required for specific drugs to determine dosing and safety profile of individual preparations.

Previous studies have explored the putative benefits of solid formulations during breastfeeding in low resource settings [15]. A variety of compounds and drugs have been studied using an in-vitro model including zinc [3, 16]. Such delivery of zinc could help in the prevention and treatment of diarrheal disease and pneumonia which are significant causes of child mortality and morbidity [16], particularly since manufacturing costs for unbranded nipple shields are considered compatible to oral syringes and applicable for low and middle income countries. Others have explored the acceptability for administering antiviral agents to prevent mother-to-child transmission of HIV through breastfeeding [17]. Our research now is important as the first in-vivo study with mothers and infants, and therefore is a step change in realizing this potential.

Undertaking this study within a Neonatal referral service in the UK has also highlighted the potential of such an intervention to support breastfeeding mothers and their infants in this high-resource setting. Oral syringes, although often considered as non-invasive by the clinical team, evoked significant negative maternal responses. In contrast, despite some pre-conceptions about the use of nipple shields, none of the mothers reported any difficulties with their use. In addition, since past literature has shown that ultra-thin contact nipple shields have the potential to increase milk transfer for preterm infants and to prolong the duration of mothers breastfeeding, use even for young infants can be considered beneficial [18-20]. However, this study focused on infants prior to discharge home, and although nipple shields can be used with older infants we cannot comment on the impact on drug delivery to infants over 6 months of age.

Some of the mothers in this study had experienced the stresses of caring for an infant in intensive care. For these mothers, it was apparent that they perceived this study intervention as a more ‘natural’ method of drug delivery and a potential opportunity for further establishing maternal infant bonding, and for them to take back ownership. This is an important part of building confidence in parents ability to take responsibility for their infant’s care [21-25]. Further studies would be important to understand the emotional impact of such an intervention in a wider cultural context. Ultimately, use of the nipple shield device for medication delivery would require either the usage of existing dosage forms that are shown to reliably disintegrate in breast milk within the duration of one breastfeed or the focused development of novel dosage forms within hospital facilities under CE-certified process or industrial partners. Provisional discussions with MHRA suggest that drug delivery in this way for regulatory purposes would be classified as a combination product.

None of the infants in this study showed baseline vitamin B12 deficiency, but all showed a significant increase in levels from baseline following a single interventional feed. In contrast, vitamin B12 deficiency is common in many low- and middle-income countries and in vegan mothers. Severe vitamin B12 deficiency is harmful to the developing infant brain, subclinical vitamin deficiency has been associated with decreased cognitive performance and supplementation can be beneficial [26]. The increase in levels did not show any relation to baseline levels or gestational age, and further studies would be needed on individual drugs to explore pharmacodynamics of this route of drug delivery and implications for dosing.

This is a single center study with a limited sample size, intentionally chosen to enable proof-of-concept assessment while reducing unnecessary infant exposure. Only mothers willing to use a nipple shield provided their consent, and therefore the sample may be biased towards a more favorable evaluation. However, approximately half the participants had not used a nipple shield previously, and only 5% of mothers declined participation due to concerns about its use. As each infant only experienced one interventional feed, the impact of repeated drug delivery in this way on latch would need further investigation. In this study, tablet taste did not appear to impact on feeding, and complete tablet delivery was achieved, which may reflect the infant’s acceptance of a variety of tastes and that milk may have taste masking properties [27-30]. However, individual formulations would require testing to determine the impact of taste or texture during breastfeeding, and formulation adjustments as needed. While many paediatric formulations include taste masking techniques, excipients used in the neonatal population should be limited. ‘However, it would be important to determine the potential impact of taste, as the bitter taste of some medicines might cause aversion to breast feeding, and adjustment to formulations would be required to insure compliance. There may be benefits from the nipple shield delivery if breastmilk is proven to provide taste masking effects”.

Conclusion

As the first in-vivo study, this study demonstrate a potential step change in drug delivery in breastfeeding infants. Along with demonstrating practical feasibility, this study has highlighted the importance of maternal preferences and potential impact on infant bonding. However, detailed further studies are needed to investigate the potential range of therapeutic formulations and to explore practical therapeutic uses.

TREND statement checklist.

(PDF)

Click here for additional data file.

Comparison of maternal expectations before and experiences after vitamin delivery during breastfeeding using a commercial nipple shield.

(DOCX)

Click here for additional data file.

Summary of maternal experience and assessment of breastfeeding during vitamin B12 delivery via a nipple shield whilst feeding.

(DOCX)

Click here for additional data file.

Summary of maternal acceptability of medicine and nutrient delivery during breastfeeding using a commercially available ultrathin contact nipple shield whilst feeding.

(DOCX)

Click here for additional data file.

(DOC)

Click here for additional data file.

COREQ (consolidated criteria for reporting qualitative research) checklist.

(DOCX)

Click here for additional data file.

10 May 2021

PONE-D-20-38364

Drug delivery from a solid formulation during breastfeeding – a clinical feasibility study with mothers and babies

PLOS ONE

Dear Dr. Beardsall,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Jun 15 2021 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see:  http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols . Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at  https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols .

We look forward to receiving your revised manuscript.

Kind regards,

Nancy Beam, PhD

Staff Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1) Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2)  Thank you for submitting your clinical trial to PLOS ONE and for providing the name of the registry and the registration number. The information in the registry entry suggests that your trial was registered after patient recruitment began. PLOS ONE strongly encourages authors to register all trials before recruiting the first participant in a study.

As per the journal’s editorial policy, please include in the Methods section of your paper:

i) your reasons for your delay in registering this study (after enrolment of participants started);

ii) confirmation that all related trials are registered by stating: “The authors confirm that all ongoing and related trials for this drug/intervention are registered”.

3) In the Methods section of the manuscript please address the following:

a) Please specify when the baseline blood samples of the infants were taken as according to the protocol

b) Please clearly state the primary and secondary outcomes of the study

c) Please specify the date ranges over which you have recruited the participants

d) When reporting the results of qualitative research, we suggest consulting the COREQ guidelines: http://intqhc.oxfordjournals.org/content/19/6/349. In this case, please consider including more information on the number of interviewers, their training and characteristics; and please provide the interview guide used.

4) There is a discrepancy on the total number of participants recruited for the study described in the manuscript text and the online registry. Please provide some further clarification for this. Furthermore, it is stated that the mothers will participate in a pre-intervention interview in the protocol, however this is not stated in the manuscript text. Please provide this information in the body of the manuscript.

5) PLOS requires an ORCID iD for the corresponding author in Editorial Manager on papers submitted after December 6th, 2016. Please ensure that you have an ORCID iD and that it is validated in Editorial Manager. To do this, go to ‘Update my Information’ (in the upper left-hand corner of the main menu), and click on the Fetch/Validate link next to the ORCID field. This will take you to the ORCID site and allow you to create a new iD or authenticate a pre-existing iD in Editorial Manager. Please see the following video for instructions on linking an ORCID iD to your Editorial Manager account: https://www.youtube.com/watch?v=_xcclfuvtxQ

6) Please amend either the title on the online submission form (via Edit Submission) or the title in the manuscript so that they are identical.

7) Please provide a caption for Figure 1.

8) Please ensure that you refer to Figure 1 in your text as, if accepted, production will need this reference to link the reader to the figure.

9) Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information.

10) We noted in your submission details that a portion of your manuscript may have been presented or published elsewhere. part of an oral presentation at the European Society for Developmental Perinatal and Paediatric Pharmacology Congress (doi: http://dx.doi.org/10.1136/archdischild-2019-esdppp.18 )

Please clarify whether this conference proceeding  was peer-reviewed and formally published. If this work was previously peer-reviewed and published, in the cover letter please provide the reason that this work does not constitute dual publication and should be included in the current manuscript.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: No

Reviewer #2: Partly

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: No

Reviewer #2: No

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: A clinical feasibility study was conducted which aimed to explore the potential to deliver medicine to infants via a solid formulation during breastfeeding in n=43 infant mother dyads. The delivery of Vitamin B12 through a solid formulation that dissolved in human breast milk did not impair breastfeeding. Furthermore, Vitamin B12 levels increased in all infants at 6-8 hours post-delivery. Eighty-five percent of mothers preferred the solid formation over syringe delivery.

Major revisions:

1- Include a statistical analysis section which summarizes all the statistical methods and cites the statistical software used for the analysis.

2- State and justify the study’s target sample size with a pre-study statistical power calculation.

Minor revisions:

1- In addition to summarizing the mean and range for continuous variables, provide standard deviations.

2- Table 3: Consider presenting these summary results in a graphic format. Specify the type of summary statistics presented.

3- Indicate the date range subjects were included in the study.

Reviewer #2: The study is the first to perform in vivo investigation in using nipple shield for drug delivery to infants and provides useful insight in the use. However, there are limitations to the study which require further consideration.

Minor points:

1. Line 21-23, please specify drug delivery to infants.

2. Line 63-64, specify blood of the infant.

3. Please check position of reference citation in the text. It should be before the full stop of the sentences.

Major points:

1. Please provide more information on the VB12 tablet: dimension, ingredients, total weight of the tablet, in vitro properties (disintegration, dissolution).

2. Please provide further description on the nipple shield, any pictures after the tablet is fitted? Whether the fitting of the tablet related to the tablet size, e.g. tablet too small might fall?

3. The major issue of the study is the huge variation of the VB12 serum concentration. The % increase differs massively (nearly 100 times the highest to the lowest). What would be the reason of this, if the dose was completed for every case as observed? Is this because of dose accuracy or absorption variation? This would be unacceptable to deliver medicines. Have the authors compared their data with previous literature on VB12 PK in paediatrics? This needs to be discussed and the limitation clearly stated.

4. The authors have mentioned taste issues. it is a good point that milk might mask the bitter taste of medicines. To which extend? How the medicines taste and dose affect this? What would be the taste masking strategy available? Need more discussion.

5. How long were the breadfeeding last? This would affect the disintegration and dissolution of the tablet.

6. Would the use of the shield become extemporaneous preparation of the medicine? what would be the regulatory indications?

7. The infants in this study are very young. Would older children (e.g. over 6 months) be more aware of the shield and impacted by the delivery?

8. The authors mentioned the use in LMIC. What is the implications on cost of the shield? Would the formulation needs to be specially designed and developed (a sublingual tablet is available for this API but might not be available for others) and would this increase cost?

9. It is true that this is a proof-of-concept study but the conclusion was quite strong in recommending this type of delivery. The authors need to have more careful and balanced evaluation of the technology to be able to provide this type of recommendation/conclusion. Otherwise, it could be misleading if it was taken out of the context.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

15 Jun 2021

15th June 2021

Re: Manuscript Number: PONE-D-20-38364

Drug delivery from a solid formulation during breastfeeding – a feasibility study with mothers and infants

Dear Ms Beam,

Many thanks for your kind response with regard to the article entitled “Drug delivery from a solid formulation during breastfeeding – a clinical feasibility study with mothers and infants” for publication in PLOS ONE. We have carefully considered the reviewers’ comments, and much appreciate their suggestions. We have made the suggested changes and provide details of further information / explanations listed below.

All the changes made to the manuscript are indicated via tracked changes. A detailed response to the reviewers’ comments can be found on the following page.

We hope that the changes made will be to your and the reviewers’ complete satisfaction, but do let us know if you require any further information.

Sincerely,

Dr Kathryn Beardsall

Detailed response to the editor’s and reviewers’ comments

Editor

Editor’s comment 1: Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming.

Corresponding author’s response 1: The manuscript was alignment with the PLOS ONE style requirements.

Editor’s comment 2: Thank you for submitting your clinical trial to PLOS ONE and for providing the name of the registry and the registration number. The information in the registry entry suggests that your trial was registered after patient recruitment began. PLOS ONE strongly encourages authors to register all trials before recruiting the first participant in a study. As per the journal’s editorial policy, please include in the Methods section of your paper: i) your reasons for your delay in registering this study (after enrolment of participants started); ii) confirmation that all related trials are registered by stating: “The authors confirm that all ongoing and related trials for this drug/intervention are registered”.

Corresponding author’s response 2: The following statement has now been included in the method section of the revised manuscript: “The study was registered and released on 8 July 2018, prior to the start of patient recruitment. It was released to the public following review by the PRS protocol team on 10 January 2019. The authors confirm that there are currently no ongoing and related trials for this drug/intervention and that all existing ones were registered.” Proof of the first submission date of 8 July 2018 can be found on https://clinicaltrials.gov/ct2/show/record/NCT03799367 when clicking on the tab “Tabular view”, under the heading “First Submitted Date”.

Editor’s comment 3: In the Methods section of the manuscript please address the following: a) Please specify when the baseline blood samples of the infants were taken as according to the protocol; b) Please clearly state the primary and secondary outcomes of the study; c) Please specify the date ranges over which you have recruited the participants; d) When reporting the results of qualitative research, we suggest consulting the COREQ guidelines: http://intqhc.oxfordjournals.org/content/19/6/349. In this case, please consider including more information on the number of interviewers, their training and characteristics; and please provide the interview guide used.

Corresponding author’s response 3: The following paragraphs were added to the manuscript (added information shown as underlined text):

a) “A baseline blood sample (full blood; heal brick) was taken within a week prior to the study feed and a peak level at 6 - 8 hours after the study feed.”

b) “Assessments included quantitative measurements of serum vitamin B12 levels at baseline and 6 - 8 hours after the interventional breastfeed, and a mixed methods assessment of maternal expectations, experience, and acceptability by a single investigator to provide for consistency.” and “Primary outcome measure is the detection of the change in vitamin B12 concentration in the infants' blood 6-8 hours after the vitamin B12 delivery from a nipple shield during breastfeeding during breastfeeding. Secondary outcome measures is the qualitative assessment of impact on maternal expectation, experience and acceptability.”

c) “Mother-infant dyads were recruited from 9 July until the end of December 2019. Following completion of the post-feed interview, enrolment in the study for a respective mother-infant dyad was completed.”

d) “The interviewer was a female researcher on the unit and trained in line with the institution’s guidelines for clinical research. Interviews were led by only one interviewer for consistency.”

Editor’s comment 4: There is a discrepancy on the total number of participants recruited for the study described in the manuscript text and the online registry. Please provide some further clarification for this. Furthermore, it is stated that the mothers will participate in a pre-intervention interview in the protocol, however this is not stated in the manuscript text. Please provide this information in the body of the manuscript..

Corresponding author’s response 4: The following text was added to the manuscript: “The study intended to recruit a maximum of 30 mother-infant dyads. A total of 43 mothers were approached, of which 26 consented to participation in the study.”

Editor’s comment 5: PLOS requires an ORCID iD for the corresponding author in Editorial Manager on papers submitted after December 6th, 2016. Please ensure that you have an ORCID iD and that it is validated in Editorial Manager. To do this, go to ‘Update my Information’ (in the upper left-hand corner of the main menu), and click on the Fetch/Validate link next to the ORCID field. This will take you to the ORCID site and allow you to create a new iD or authenticate a pre-existing iD in Editorial Manager. Please see the following video for instructions on linking an ORCID iD to your Editorial Manager account: https://www.youtube.com/watch?v=_xcclfuvtxQ

Corresponding author’s response 5: As requested, the ORCID iD for the corresponding author has been linked to the Editorial Manager account.

Editor’s comment 6: Please amend either the title on the online submission form (via Edit Submission) or the title in the manuscript so that they are identical.

Corresponding author’s response 6: The title of the manuscript was amended to “Drug delivery from a solid formulation during breastfeeding – a clinical feasibility study with mothers and infants”.

Editor’s comment 7: Please provide a caption for Figure 1.

Corresponding author’s response 7: Figure 1 had been given a caption (see reference within “Results” section).

Editor’s comment 8: Please ensure that you refer to Figure 1 in your text as, if accepted, production will need this reference to link the reader to the figure.

Corresponding author’s response 8: Figure 1 had been referenced in the text (see “Results” section).

Editor’s comment 9: Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information.

Corresponding author’s response 9: Captions for all Supporting Information files were included at the end of the manuscript (shown below), and in-text citations updated accordingly.

Supporting Information

• Table A.1. Comparison of maternal expectations before and experiences after vitamin delivery during breastfeeding using a commercial nipple shield.

• Table A.2. Summary of maternal experience and assessment of breastfeeding during vitamin B12 delivery via a nipple shield whilst feeding.

• Table A.3. Summary of maternal acceptability of medicine and nutrient delivery during breastfeeding using a commercially available ultrathin contact nipple shield whilst feeding.

• COREQ (COnsolidated criteria for REporting Qualitative research) Checklist

Editor’s comment 10: We noted in your submission details that a portion of your manuscript may have been presented or published elsewhere. part of an oral presentation at the European Society for Developmental Perinatal and Paediatric Pharmacology Congress (doi: http://dx.doi.org/10.1136/archdischild-2019-esdppp.18). Please clarify whether this conference proceeding was peer-reviewed and formally published. If this work was previously peer-reviewed and published, in the cover letter please provide the reason that this work does not constitute dual publication and should be included in the current manuscript.

Corresponding author’s response 10: Only an abstract of the research study was formally published to introduce the content of the oral presentation at the ESDPP congress – yet this abstract was not peer-reviewed. We confirm that the manuscript has not been peer-reviewed and published.

Reviewer 1

Reviewer’s major point 1: Include a statistical analysis section which summarizes all the statistical methods and cites the statistical software used for the analysis.

Corresponding author’s response to major point 1: All data shown is presented as mean percentage or mean and ranges if normally distributed. The power calculation for the study has been added and an explanation that given the range of gestational and postnatal ages of the infants recruited exploratory analyses of these baseline characteristics was undertaken.

Reviewer’s major point 2: State and justify the study’s target sample size with a pre-study statistical power calculation.

Corresponding author’s response to major point 2: The following text was added to the manuscript: “The sample size was based on the literature for preterm infants’ supplementation, in which B12 between 8-12 weeks led to an approximate three-fold rise in serum B12 levels. As such this sample size would provide 90% power at the 5% level to demonstrate a 2 two-fold increase in B12.”

Reviewer’s minor point 1: In addition to summarizing the mean and range for continuous variables, provide standard deviations.

Corresponding author’s response to minor point 1: The following text was added to the manuscript: “Vitamin B12 levels rose in all infants from a mean baseline (range) 533 ± 188 pg/mL (236 - 925 pg/mL) to 1871 ± 1228 pg/mL (610 – 4981 pg/mL) at 6 - 8 hours post-delivery.”

Reviewer’s minor point 2: Table 3: Consider presenting these summary results in a graphic format. Specify the type of summary statistics presented.

Corresponding author’s response to minor point 2: The suggestion for a graphical illustration was carefully considered, yet a table format preferred. With regard to the summary statistics, the following text was added to the manuscript: “Numerical values are shown as mean ± standard deviation.”

Reviewer’s minor point 3: Indicate the date range subjects were included in the study.

Corresponding author’s response to minor point 3: The following text was added to the manuscript (added paragraphs / parts shown as underlined text):

• “A baseline blood sample (venous blood or heal brick) was taken within a week prior to the study feed and a peak level at 6 - 8 hours after the study feed.”

• “Mother-infant dyads were recruited from 9 July until the end of December 2019. Following completion of the post-feed interview, enrollment in the study for a respective mother-infant dyad was completed.”

Reviewer 2

Reviewer’s major point 1: Please provide more information on the VB12 tablet: dimension, ingredients, total weight of the tablet, in vitro properties (disintegration, dissolution).

Corresponding author’s response to major point 1: The following text was added to the manuscript: “The tablet characteristics comprised the following: round tablet with a diameter of 8 mm and an average weight of 0.26 g; ingredients: Sorbitol, Stearic Acid, Beetroot, Blackcurrant, Magnesium Stearate, Methylcobalamin. To investigate the vitamin B12 tablets' disintegration properties, lab-based studies were performed. Hereby, the vitamin B12 tablets were placed in the silicone teat of a 20 mm Medela ultrathin contact nipple shield, and delivery into full-fat cow's milk investigated in triplicate using a breastfeeding simulation apparatus, capable of simulating both the process of lactation and infant feeding by mimicking the average flow rates/patterns of milk during breastfeeding and the infant’s suckling pressure at physiological relevant conditions. The percentage of tablet released within 5, 10 and 20 min was approximately 41%, 62%, and 74% respectively, and no tablet break-offs during disintegration or dislocation of the remaining tablet through the silicone teat's three holes following the experiment was observed.”

Reviewer’s major point 2: Please provide further description on the nipple shield, any pictures after the tablet is fitted? Whether the fitting of the tablet related to the tablet size, e.g. tablet too small might fall?

Corresponding author’s response to major point 2: The following text was added to the manuscript (added paragraphs / parts shown as underlined text): “Commercial ultrathin contact nipple shields (Medela, UK) of 16 mm (size S), 20 mm (size M), or 24 mm (size L) size, as recommended by the lactation support team, and following evidence from an earlier scoping exercise with mothers (1), were selected and worn by mothers during the study feed. These nipple shields are commonly used on the hospital’s maternal and neonatal wards, made from transparent BPA- and taste-free soft silicone.”

Reviewer’s major point 3: The major issue of the study is the huge variation of the VB12 serum concentration. The % increase differs massively (nearly 100 times the highest to the lowest). What would be the reason of this, if the dose was completed for every case as observed? Is this because of dose accuracy or absorption variation? This would be unacceptable to deliver medicines. Have the authors compared their data with previous literature on VB12 PK in paediatrics? This needs to be discussed and the limitation clearly stated.

Corresponding author’s response to major point 3: The following text was added to the manuscript: “This feasibility study used B12 only as a marker of utility for the novel delivery approach, not as a therapeutic option or to explore pharmacokinetic uptake in infants. However, the findings do raise an important observation of the complexities of bioavailability in the newborn not related only to breastfeeding, but also to gut pathology, postnatal age, and gestational age. Findings of this study seemed to suggest that vitamin B12 absorption was dependent on postnatal age and independent of prematurity or birth weight (total absorption: 0.0072 ± 0.0029 % for infants <7 days of age, and 0329 ± 0.0173 % infants aged 19 − 70 days). Given the small sample size, no conclusive statement can be made, and further investigations would be required but the findings are in keeping with the literature”

Reviewer’s major point 4: The authors have mentioned taste issues. it is a good point that milk might mask the bitter taste of medicines. To which extend? How the medicines taste and dose affect this? What would be the taste masking strategy available? Need more discussion.

Corresponding author’s response to major point 4: The following text was added to the manuscript (added paragraphs / parts shown as underlined text): “However, individual formulations would require testing to determine the impact of taste or texture during breastfeeding, and formulation adjustments as needed. While many formulations include taste advancements, masking ingredients are generally avoided in the neonatal population and there may be benefits from this route and the masking effects of milk on the taste of the medication.”

Reviewer’s major point 5: How long were the breastfeeding last? This would affect the disintegration and dissolution of the tablet.

Corresponding author’s response to major point 5: The following text was added to the manuscript: “The mean duration of the study feeds (n=20) was 19.8 ± 5.5 min (Range 15 – 30 min).”

Reviewer’s major point 6: Would the use of the shield become extemporaneous preparation of the medicine? what would be the regulatory indications?

Corresponding author’s response to major point 6: The following text was added to the manuscript: “Ultimately, use of the nipple shield device for medication delivery would require either the usage of existing dosage forms that are shown to reliably disintegrate in breast milk within the duration of one breastfeed or the focused development of novel dosage forms within hospital facilities under CE-certified process or industrial partners. Provisional discussions with MHRA suggest that drug delivery in this way for regulatory purposes would be classified as a combination product”

Reviewer’s major point 7: The infants in this study are very young. Would older children (e.g. over 6 months) be more aware of the shield and impacted by the delivery?

Corresponding author’s response to major point 7: The following text was added to the manuscript: “This study focused on infants prior to discharge home, and although nipple shields can be used with older infants we cannot comment on the impact on drug delivery to infants over 6 months of age.”

Reviewer’s major point 8: The authors mentioned the use in LMIC. What is the implications on cost of the shield? Would the formulation needs to be specially designed and developed (a sublingual tablet is available for this API but might not be available for others) and would this increase cost?

Corresponding author’s response to major point 8: The following text was added to the manuscript:

• “Such delivery of zinc could help in the prevention and treatment of diarrheal disease and pneumonia which are significant causes of child mortality and morbidity (13), particularly since manufacturing costs for unbranded nipple shields are considered compatible to oral syringes and applicable for low and middle income countries.”

• “Ultimately, use of the nipple shield device for medication delivery would require either the usage of existing dosage forms that are shown to reliably disintegrate in breast milk within the duration of one breastfeed or the focused development of novel dosage forms within hospital facilities under CE-certified process or industrial partners.”

Reviewer’s major point 9: It is true that this is a proof-of-concept study but the conclusion was quite strong in recommending this type of delivery. The authors need to have more careful and balanced evaluation of the technology to be able to provide this type of recommendation/conclusion. Otherwise, it could be misleading if it was taken out of the context.

Corresponding author’s response to major point 9: The following text was added to the manuscript: “However, detailed further studies are needed to investigate the potential range of therapeutic formulations and to explore practical therapeutic uses.”

Reviewer’s minor point 1: Line 21-23, please specify drug delivery to infants.

Corresponding author’s response to minor point 1: The following addition was made to line 21-23 (see underlined text): “ In low-resource settings the delivery of medications, such as de-worming and retrovirals as well as nutrient and mineral supplementation, in liquid formulations is challenging, as liquids need to be refrigerated for storage, and syringes require clean water for sterilization”

Reviewer’s minor point 2: Line 63-64, specify blood of the infant.

Corresponding author’s response to minor point 2: The following addition was made to line 21-23 (see underlined text): “A baseline blood sample (full blood; heal brick) was taken prior to and a peak level at 6 - 8 hours after the study feed.”

Reviewer’s minor point 3: Please check position of reference citation in the text. It should be before the full stop of the sentences.

Corresponding author’s response to minor point 3: The position of reference citation in the text was reviewed and adjustments made in line with the requirements.

6 Oct 2021

24 Nov 2021

Re: Drug delivery from a solid formulation during breastfeeding – a feasibility study with mothers and infants

Manuscript Number: PONE-D-20-38364R1

Dear Jamie Males,

Many thanks for your helpful comments with regard to the full-length research article entitled “Drug delivery from a solid formulation during breastfeeding – a clinical feasibility study with mothers and babies” for publication in PLOS ONE. We have carefully considered the reviewers’ comments, and appreciate their suggestions. We have provided further information / explanations to paragraphs of the manuscript as enquired by you and the reviewers.

All the changes made to the manuscript are indicated via tracked changes. A detailed response to the reviewers’ comments can be found on the following page.

We hope that the changes made are to your and the reviewers’ complete satisfaction.

Sincerely,

Dr. Kathryn Beardsall

Detailed response to the reviewers’ comments

In the following both the reviewers’ comments, as well as the actions taken are illustrated.

Reviewer 1

Minor point: Line 114 – Indicate the statistical testing method which achieves 90% power.

Response: Thank you we have added (two sided superiority) to clarify.

Reviewer 2

Minor point 1: In the marked up manuscript line 230-232,

a) "Given the small sample size, no conclusive statement can be made, and further investigations would be required but the findings are in keeping with the literature on B12.", can you please specify "no conclusive statement can be made" on what?

The text was amended to

“Given the small sample size, no conclusive statement can be made about the interdependency between postnatal age and vitamin B12 absorption, and further investigations are required.”

b) Also please specify e.g. "keeping with the literature on B12 absorption in infants" and provide literature references.

References were added as requested: “This is a feasibility study but based on the literature for preterm infants’ supplementation, in which B12 between 8-12 weeks led to an approximate three-fold rise in serum B12 levels (9,10).”

Minor point 2: The authors have commented that oral syringe would need to be sterilised which is a disadvantage in LMICs. Would the nipple shield need to be sterilised before use?

Response: The initial suggestion was for a disposable or biodegradable nipple shield to avoid the need for sterilization but given that this was a proof of principle in a level 3 unit in the UK we thought this distracted from the main message of the paper.

Minor point 3: This sentence needs to be written clearer "While many formulations include taste advancements, masking ingredients are generally avoided in the neonatal population and there may be benefits from this route and the masking effects of milk on the taste of the medication." For example "While many paediatric formulations include taste masking techniques, excipients used in the neonatal population should be limited. There may be benefits from the nipple shield delivery if breastmilk is proven to provide taste masking effects.”

Response: Thank you we have amended as suggested

Minor point 4: Please also add a statement to the above sentence that the bitter taste of some medicines might cause aversion of infants to breastfeeding.

Response: The following sentence has been added. ‘However, it would be important to determine the potential impact of taste, as the bitter taste of some medicines might cause aversion to breast feeding, and adjustment to formulations would be required to insure compliance.’

Submitted filename: Response to Reviewers_v15 Nov 2021 stand alone.docx

Click here for additional data file.

21 Jan 2022

24 Jan 2022

25th Jan 2022

Re: Drug delivery from a solid formulation during breastfeeding – a feasibility study with mothers and infants

Manuscript Number: PONE-D-20-38364R1

Dear Jamie Males,

Many thanks for your helpful comments with regard to the full-length research article entitled “Drug delivery from a solid formulation during breastfeeding – a clinical feasibility study with mothers and babies” for publication in PLOS ONE. We have addressed the outstanding request to include details of statistical methodology and this is highlighted in the manuscript.

We hope that the changes made are to your complete satisfaction. Please let us know if you require any further information.

Sincerely

Dr Kathryn Beardsall

17 Feb 2022

Drug delivery from a solid formulation during breastfeeding – a clinical feasibility study with mothers and infants

PONE-D-20-38364R3

Dear Dr. Beardsall,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Sourabh Dutta

Academic Editor

PLOS ONE

Additional Editor Comments (optional): None

Reviewers' comments: None

24 Feb 2022

PONE-D-20-38364R3

Drug delivery from a solid formulation during breastfeeding – a feasibility study with mothers and infants

Dear Dr. Beardsall:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Sourabh Dutta

Academic Editor

PLOS ONE