Prediction of pharmacokinetic values of two various dosages of caffeine in premature neonates with apnea.

OBJECTIVES: Despite extensive caffeine use in preterm infants, the pharmacokinetics (PKs) data are limited because of the studies are complicated to do in these patients. This research was investigated the PK profile of two various dosages of caffeine in premature neonates.
MATERIALS AND METHODS: The PK values of caffeine in premature neonates with Apnea were predicted by using all of computer-based simulation (Simcyp®), population-based PK, and modeling (P-Pharm®). We assayed the plasma levels of caffeine in two groups. The information was analyzed utilizing nonlinear mixed-effects modeling approach. The PK parameters were assessed simulating virtual clinical considers with subjects got 20 mg. kg-1 of caffeine in both groups, which was followed by a 5 mg. kg-1 once daily in Group 1 or 2.5 mg. kg-1 twice daily in Group 2. All statistical analysis was executed utilizing SSPS issue 19 and a P value of 0.05 was chosen significance.
RESULTS: In the present study, the means CL, volume of distribution, and T1/2 of caffeine in preterm infants were 0.0476 L. h-1, 1.1081 L, 16.2284 h, respectively. Whereas our simulated means by Simcyp were 0.090 L. h-1, 1.841 L, and 14.653 h in Group 1 and 16.223 h in Group 2, respectively.
CONCLUSIONS: There was overall good agreement between predicted and measured PK values in our study. This study provides an initial demonstration of Simcyp simulation advantage on anticipating of PK parameters.

Introduction

Apnea of prematurity is a prevalent disease, result in an imperfection of the respiratory control system and unstable respiratory drive in premature infants.[12345] Caffeine as a favorable methylxanthine has stimulant effects of the respiratory system, which is the standard pharmacological treatment for apnea in premature neonates. The current standard loading and maintenance dosages of caffeine involve a 20 mg per kg and 5 mg per kg per day, respectively.[67]

A safe therapeutic plasma concentration is in the range of 3 mg/L to 84 mg/L.[8] The defensive effects of caffeine on the brain and lungs are major benefits of caffeine, yet there are few side effects on the preterm infants.[101112131415] Caffeine increase the respiratory muscle strength, the diaphragmatic activity, and the tidal volume.[1617] Furthermore, it reduces the occurrence of Bronchopulmonary Dysplasia, it decreases the length of continuous positive airway pressure and mechanical ventilation in premature newborns.[9181920] Despite the extensive use of caffeine in premature neonates, Pharmacokinetics (PKs) data are limited; because these studies are complicated to carry out in these patients. Some of these studies are available.[91821] It has reported that caffeine clearance (CL) was very slow, and its half-life was prolonged.[22] Another study showed the CL and volume of distribution (Vd) notably impacted by after the birth age and body weight, while Vd was higher in more advanced infants.[23] It has proposed that caffeine improves ventilation in 8–20 mg/L plasma concentration, mostly through improving central respiratory drive.[24] Some studies have examined how various dosages of caffeine can improve the respiratory action of premature newborns; high dose caffeine equivalent to 20 mg per kg per day decreases the require for respiratory backing; meanwhile, the standard dosage regimen (5 mg per kg per day) lead to no adverse results at 2 years old.[25] The higher concentrations are related to the lower duration of hospitalization, time of ventilation, and the time of oxygen at discharge.[26] It has shown that the caffeine concentration is not related to the frequency of apnea within 7 days of the drug discontinuation, the therapeutic range is 11–12 days.[27] Nevertheless, studies of caffeine PKs regarding the premature infant were limited and there is little data available. Therefore, this research was planned to investigate the PKs profile of caffeine in premature neonates. Moreover, we assayed the plasma levels and the divided caffeine dosing regimens in these patients.

Materials and Methods

This study conducted at neonatal intensive care center of Boo-Ali Sina Pediatrics Hospital, from July 2015 to August 2016. Patients between the ages of 26–37 weeks entered into the trial with evidence of apnea, and they had been administered caffeine by a neonatologist. Patients with the following conditions were excluded from the study; having underlying diseases, treatment with methylxanthine in the past. Caffeine was from Chemidarou Pharmaceutical Co. Ltd., (Tehran, Iran). Perchloric acid and methanol for High-performance liquid chromatography (HPLC) were prepared from Merck (Darmstadt, Germany). Deionized water utilized in the procurement of mobile phase. Blank plasma utilized for calibration and approval of the trial was gotten from Healthy volunteers. Forty infants were randomized into two groups, each group gotten a loading dose of 20 mg per kg of caffeine intravenously for the primary ½ h, taken after a maintenance dose of 5 mg per kg daily for Group 1 and 2.5 mg per kg twice daily for Group 2 over 20 min.

The PKs values for caffeine in premature neonates with apnea were predicted by utilizing all of computer-based simulation (Simcyp®), population-based (PB)-PK and modeling (P-Pharm®). The study protocol was morally approved. As well as an informed signed consent was approved by all patients' parents.

Study design

Up to 3 blood samples were drawn from each patient via peripheral vein after 30 min of the loading dose, 30 min after the first maintenance dose, and 72 h after initiation of caffeine, the initiation of caffeine must be before intravenous (IV) administration. Plasma was provided and maintained at −20°C till analysis.

Bioanalytical

Plasma concentrations of caffeine were determined using the Euro chrome software of HPLC on a Knauer C8 column with 150 × 4 millimeter i. d. and 5 micrometer bit dimension. The mobile phase comprised methyl alcohol and distilled water (pH = 6) (30/70, v/v). The calibration range of the assay was 50–1000 ng ml.[1] Examinations operate at a flow rate of 0.9 ml per min at environment temperature. The wavelength was put on 280 nm, and the peak areas were gauged. The working solution of caffeine citrate attenuated with drug-free plasma to impute the calibration standards at concentrations of 10, 20, 30, 40, and 50 μg/ml caffeine.

Pharmacokinetic analysis

Population pharmacokinetic analysis

This study also employed a small exampling trial plan to assessment caffeine PK parameters. Caffeine concentration information over the time was assayed utilizing nonlinear mixed-effects model, which was executed in P-PHARM French issue 1.5.1 software. The PKs parameters of caffeine were assessed simulating virtual clinical trials with subjects getting 20 mg per kg loading dose of the drug in two groups, which was continued with 5 mg per kg dose of the drug once daily in the first series of patients or 2.5 mg per kg twice a day in the second series of patients.

Simulations of pharmacokinetic profiles of caffeine using Simcyp®

Caffeine PKs was simulated utilizing the full PB PK pattern executed in the Simcyp Pediatric PB Simulator (issue 13.2, UK). In vitro information portraying the physicochemical properties of caffeine is summarized in Table 1. Age, dosage, dosage spacing, and duration of caffeine injection put confirming to the clinical study. Patient's simulations were executed utilizing 500 patients aged <1 month, in 10 trials, with each trial containing 50 subjects. All parameters were achieved from the pediatric patient's library inside a pediatric issue of Simcyp. A summary of input parameters in Simcyp is shown in Table 2.

Table 1

Physiochemical characteristics of caffeine

Compound name	Caffeine
Mol weight (g/mol)	192.190
log Paa	−0.070
Compound type	Monoprotic base
pKa 1b	1.050
pKa 2	N/A
B/Pc	0.977
Haematocrit	45.000
Fud	0.680

aLog P logarithm of the octanol-water partition coefficient, bpKa acid dissociation constant, cB/P blood to plasma ratio, dfu fraction unbound in plasma. N/A=Not available

Table 2

A summary of input parameters of caffeine in simcyp

Population name	Paediatric
Population size	500
Number of trials	10
Number of subjects per trial	50
Start day/time	Day 1, 09:00
End day/time	Day 6, 09:00
Study duration (h)	120
Number of time samples	200
Trial design	Trial1	Trial2
Dosing time	Day 1, 09:00	Day 1, 09:00
Dosing regimen	Multiple dose	Multiple dose
Dose interval (h)	24	12
Number of doses	5	10
Fasted/fed	Fasted	Fasted

Statistical analysis

Qualitative factors were registered by frequency and percent and quantitative factors by mean ± standard deviations. Whole statistical analyses were executed utilizing SPSS issue 19 (SPSS Inc., Chicago, IL, USA). The level of significance of 5% was selected. Caffeine concentration information over the time was assayed utilizing nonlinear mixed-effects model, which was executed in P-PHARM French issue 1.5.1 software. PK information was coordinated with various PK patterns and the most compatible pattern elected.

Results

Patient characteristics

Forty-seven neonates listed in this trial and forty patients complied trial criteria. Seven of them divested the study; two neonates because of hypoglycemia, two of the seven patients due to congenital anomaly, one of them were divested due to his intra-ventricular hemorrhage, and two patients due to death. Demographic and clinical properties of patients in two series are displayed in Table 3.

Table 3

Demographic and clinical characteristics of the patients in two study groups

Subject	All subject	Group 1g	Group 2h	Pi
Number of patients	40	20	20
Gender: Female/male, n (%)	20/20 (50/50)	11/9 (55/45)	9/11 (45/55)	0.52
GA at birth (week)/mean±SD	32.27±3.23	32.2±3.06	32.34±3.46	0.89
BW (g)/mean±SD	1824.5±702.54	1772±675.27	1877±742.5	0.64
Vaginal delivery, n (%)	3 (7.5)	1 (5)	2 (10)	0.54
Apgar, 1 minc/median (IQR)	9 (8–9)	9 (8–9)	9 (9–9)	0.32
Apgar, 5 mind/median (IQR)	10 (9–10)	10 (9–10)	10 (9.25–10)	0.86
RDS scoree/median (IQR)	6 (4–7)	6 (4.25–7)	5.5 (4–7)	0.49
Surfactant (INSURE), n (%)	19 (47.5)	12 (60)	7 (35)	0.11
PNA at initiation of caffeine (days) (mean±SD)	8.23±9.2	7.1±7.7	6.7±7.2	0.86

cApgar score in 1th min after birth, dApgar score in 5th minutes after birth, eRespiratory distress syndrome score at the time of admission, gGroup 1: Once daily administration of caffeine, hGroup 2: Two divided dose daily administration of caffeine, iIndependent sample t-test was used. GA=Gestational age, BW=Birth weight, SD=Standard deviation, IQR=Interquartile range, INSURE=Intubate-surfactant-extubate, PNA=Postnatal age, RDS=Respiratory distress syndrome

Statistical analysis revealed that there was no statistically significant difference in terms of clinical properties among patients of two groups (P ≥ 0.2).

Pharmacokinetics analysis

A one-compartment steady-state PK pattern with first-level dispensational level constants and first-level elimination supplied a notably suitable concentration-time profile than other patterns. A Heteroscedastic error model (1/y^2) was fitting for all the measures. A lognormal dispensation best explained the inter-person variation in all population pharmacokinetic (POPPK) parameters. The population-derived Bayesian predicted versus observed total plasma concentrations at steady state is appeared in Figure 1.

Figure 1

The population-derived Bayesian predicted versus observed total plasma concentrations of caffeine at steady state calculated from best-fitted model

After coordinating the one compartment model, the predicted plasma concentrations of caffeine were followed by IV infusion with 24 h (study 1) and 12 h (study 2) intervals displayed in Figure 2.

Figure 2

The predicted total plasma concentrations curve of caffeine after fitting to the one –compartment model following intravenous administration with 24 h (study 1) or 12 h intervals (study 2)

Analytical analysis

The present HPLC assay is simple, sensitive, and gave chromatograms with adequate separation of caffeine. A representative chromatogram of the drug is shown in Figure 3. Under the chromatographic situation utilized, caffeine (retention time 8.18 ± 0.042 min), gave quickly eluting, entirely settled, and basically symmetrical peaks [Figure 4]. Calibration curves for the caffeine over known concentration span were linear (R2 = 0.998) [Figure 3].

Figure 3

Representative calibration curves for the analysis of caffeine by high-performance liquid chromatography

Figure 4

Reconstructed chromatogram following the analysis of blank plasma spiked with 40 μg/ml of caffeine

The Simcyp® simulation was conducted using a design that reflected the clinical study design of caffeine. The mean plasma concentrations of caffeine after simulation by SIMCYP followed by IV infusion with 24 (study 1) and 12 (study 2) h intervals are shown in Figure 5.

Figure 5

Systemic simulated the mean plasma concentrations of caffeine after intravenous infusion with 24 and 12 h intervals

The mean values of PKs parameters of caffeine in 500 virtual subjects simulated from in vitro data using SIMCYP software after IV infusion with 12 and 24 h intervals are presented in Table 4.

Table 4

Mean values of pharmacokinetic parameters of caffeine in 500 virtual subjects simulated from in vitro data using simcyp

1.1.1. PKPD profile	Cmax (ng/ml)	T ½ (h)	Vd (L)	Clearance (L/h)
Mean±CI
Study-1a	6033.09±5605.26	14.653	1.841	0.090
Study-2	9476.39±8606.80	16.223	1.841	0.090
Minimum
Study-1	5313.21	1.333	0.659	0.014
Study-2	8159.58	14.289	0.659	0.014
Maximum
Study-1	5378.79	21.932	5.069	0.488
Study-2	8215.81	21.932	5.069	0.488
Fold change
Study-1	5161.46	16.46	7.70	35.92
Study-2	7842.59	1.53	7.70	35.92

aOnce daily IV infusion of the caffeine: Study 1/: Two divided dose IV infusion of the caffeine: Study 2. CI=Confidence interval, PKPD=Pharmacokinetic/ pharmacodynamic

Pharmacokinetic parameter values for caffeine

A summary of PK parameters includes T1/2 beta, a Vd and CL of caffeine in our infant patients following 24-h or 12 h intervals of drug administration are shown in Table 5.

Table 5

A summary of pharmacokinetic parameters of caffeine in preterm infants after 24-h (Study 1) or 12 h (Study 2) IV infusion of the drug

Study Average	Cl (L/h)	Vd (L)	T1/2 beta (h)
All	0.0476±0.0037	1.1081±0.0220	16.2284±1.3327
Study-1	0.0475±0.0030	1.1086±0.025	16.2544±1.099
Study-2	0.0478±0.0039	1.1076±0.0192	16.1967±1.5236

Discussion

In this trial, we investigated the PK profile of caffeine after intravenous administration in preterm neonates with apnea. Several studies have indicated the PKs of caffeine in premature neonates.

Aranda et al., in 1979, reviewed the PK profile of caffeine by using a first-order one-compartment model in preterm infants. Based on results, the mean CL, Vd and T½ values of caffeine were estimated to be 8.9 ml per h per kg (0.0089 L. h−1.kg−1), 0.916 L. kg−1 and 102.9 h, respectively.[9] Gorodischer studied the PKs of caffeine in 1982 in 13 premature infants with apnea. Caffeine CL was very slow, and its half-life was prolonged. The mean CL, distribution volume, and plasma half-life values of caffeine were estimated 8.5 ml per hour per kg (0.0085 L. h−1.kg−1), 0.78 L. kg−1 and 65 h, respectively.[22] Lee et al. have evaluated POPPK modeling of caffeine in premature neonates with apnea in 1997. The analysis was performed using NONMEM to estimate the parameters of the one compartment model. CL (0.012 L. h−1) and distribution volume (2.2 L) notably related to after the birth age and body weight while distribution volume was higher in more advanced neonates and half-life was 144 h.[23] In another study which carried out in 18 Asian preterm infants using P-Pharm software and a one-compartment model. The population means CL, Vd and T1/2 values of caffeine were estimated 0.00638 L. h−1, 0.9608 L, and 106 h, respectively.[21] Falcao et al. performed a POPPK study of caffeine in premature neonates. The analysis was carried out based on a non-linear mixed effect model (NONMEN) and one-compartment model. The values included: CL (L. h−1) = 0.00581* current weight (kg) +1.22* after the birth age (weeks) and distribution volume (L) = 0.911* current weight (kg).[28] The POPPKs of caffeine were studied in 60 infants. CL affected by body weight and after the birth age. Cl and Vd of caffeine stay constant during the treatment. A final analysis proved CL (Litter per hour) = 0.015 and distribution volume = 0.82 Litter.[29] A POPPKs model of caffeine was surveyed in premature neonates by Charles et al. PK values were estimated using a one-compartment model of NONMEN. CL enhanced nonlinearly with incrementing postnatal age, while distribution volume (Vd) enhanced linearly with weight, agreeing to next allometric models: CL (L. h−1) =0.016; Vd (L) =1.76. The mean of elimination half-life reported 101 h.[30] PK parameters of caffeine in premature neonates were reported by Patel et al. The POPPK model obtained using NONMEN. Final model was as follows: CL = 0.015 (L. h−1), Vd (L) =1.29, T1/2 (h) =57.[31] A POPPK model was studied utilizing NONMEM in 29 infants. The PK values were calculated based on final mode: CL (L. h−1) =0.0167, Vd (L) = 0.966.[32] In the present study, the population means CL, the Vd and half-life values of caffeine in premature neonates with apnea were 0.0476 (L. h−1), 1.1081 (L), and 16.2284 (h) respectively [Table 5]. The CL in our infants was larger than reported in previously mentioned studies. The distribution volume per kilogram was approximately alike with amounts detailed already for newborns.[21303132] However, the half-life of caffeine in this study was lower than in other studies. Regarding daily administration of caffeine in premature newborns that is routine, the half-life of 16 h seems to be more acceptable than the higher values.

The second target of the study was to compare predicted and observed PK parameters of caffeine in preterm infants with apnea. Several researchers have represented different approaches whereby PK parameters can be estimated from in vitro data. In these studies, many ways have been utilized to predict the values.[333435363738] Accurate predictions can result in reducing the costs and times that required for clinical trials.

Conclusions

This trial was carried out to assess the PK parameters of caffeine in premature newborns, which was executed in parallel with a clinical trial to assess the therapeutic outcomes of caffeine on apnea of prematurity. In the present study, the population means CL, Vd and T1/2 values of caffeine in premature newborns with apnea were 0.0476 L. h−1, 1.1081 L, and 16.2284 h, respectively. Whereas our simulated mean CL, V, and Ka values by Simcyp were 0.090 L. h−1, 1.841 L, and 14.653 h in Group 1 and 16.223 h in Group 2, respectively. There was overall good matching among predicted and measured PKs measures in our study. Furthermore, Cmax in Group 1 and 2 was 6033.09 and 9476.39 ng/ml respectively in simulated patients. However, the value of Cmax in the patients was not available because of the low number or volume of some blood samples. Given the limitations of clinical trials, especially in premature infants, this can be justified. The present study provides an initial demonstration of the potential advantage of Simcyp simulation on predicting of drugs PK parameters especially on predicting of half-life.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.