Virucidal mouth rinses for patients during the coronavirus disease 2019 outbreak.

We congratulate Dr Turkistani for the well-elucidated precautions and recommendations for orthodontic settings during the coronavirus disease 2019 pandemic (Turkistani KA. Precautions and recommendations for orthodontic settings during the COVID-19 outbreak: a review. Am J Orthod Dentofacial Orthop 2020;158:175-81). Representing a second layer of defense, prophylactic preprocedural use of oxidative mouth rinse and throat spray formulations have been suggested as an indispensable risk reduction measure for decreasing the number of viable microorganisms in dental aerosols during the current outbreak.

The author recommended using 0.12%-0.20% chlorhexidine gluconate (CHX) and referenced studies by Ge et al and Marui et al. However, the systematic review by Marui et al showed the efficacy of CHX against the bacterial load in dental aerosol and not the viral particles. We critically analyzed the in vitro study by Wood and Payne, which also showed CHX was ineffective in the inactivation of enveloped human coronavirus. A recent review by O’Donnell et al reported lower virucidal activity of CHX toward coronaviruses and recommended exploring the option of using a combination of CHX with alcohol for reducing oral bioburden over longer times.

In contrast, povidone iodine (PVP-I), a broad-spectrum oxidizing antimicrobial widely used for 60 years and with a well-established safety profile, has been shown to be an effective virucide in vitro against similar severe acute respiratory syndrome coronavirus (SARS-CoV-2) and Middle East Respiratory Syndrome viruses. , In vitro viricidal efficacy of 0.5% PVP-I oral rinse after 15 seconds contact time, and 1.0% (w/v) PVP-I oral rinse, and 0.45% (w/v) PVP-I throat spray after 30 seconds has also been recently demonstrated by Bidra et al and Anderson et al, respectively. Preliminary in vivo efficacy of 1-minute rinse with 1% PVP-I with effects lasting for up to 3 hours in real-time clinical settings involving a limited number of patients have also been recently documented. However, considering the possible confounders, including viral load and the patient's immune response, the authors recommended further clinical trials to confirm its efficacy.

A recent unpublished large-scale systematic review with network meta-analysis involving aerosol mitigation intervention processes reported 0.2%-1% PVP-I or 1% hydrogen peroxide as an effective substitute for oxidation-prone vulnerable viruses such as SARS-CoV-2. The use of PVP-I is favorable for its gradual non-PVP-bound free iodine release, thereby minimizing toxicity, and the resultant viral inactivation arising from its oxidative effect and lipid shell membrane destruction causes irreversible damage to the pathogen.

With no clinical studies supporting the virucidal effects of CHX against SARS-CoV-2, and in light of the recently emerging evidence demonstrating the in vitro and in vivo virucidal efficacy of PVP-I, it seems justifiable to recommend the innocuous use of PVP-I as a viable alternative for interrupting transmission of SARS-CoV-2. The recommendations of Kirk-Bayley et al regarding the use of 9 mL of 0.5% PVP-I as a mouthwash both for the patient and for the clinical staff should be repeated every 2-3 hours, up to 4 times a day. The authors recommend distributing the mouthwash throughout the oral cavity for 30 seconds, followed by gentle gargling at the back of the throat for another 30 seconds before spitting out. On the basis of the assumption that at least 1 mL of the solution will be retained (based on self-testing using high-accuracy scales, subtracting salivary production) and absorbed, the maximum total dose of 0.55 mg of iodine is delivered. In the case that a nasal pump atomizing device is used, the steps involve the use of 7 sprays aimed in different directions, followed by licking around the inside of the oral cavity, thereby yielding 0.54 mg of iodine (0.14 mL per actuation for most commercially available nasal atomizers at 0.077 mg iodine per actuation).

Furthermore, the authors recommend the intranasal application of 0.28-0.3 mL of 0.5% PVP-I solution into each nostril (using 2 sprays for an average atomizing device or by using a syringe), for patients and also for health care workers this should be repeated every 2-3 hours, up to 4 times a day. The effectively delivered total dose of 0.33 mg of iodine may minimize the bioaerosols from nasal cavities and nasopharynx. For maximizing coverage of the nasal cavity and nasopharynx during the atomization/instillation of the nasal spray, it has been advised to occlude the contralateral nostril and keep the mouth closed.