Povidone iodine gargle and mouthwash.

Sir, a recent letter in your journal by Challacombe et al. highlighted the potential of povidone iodine (PVP-I) mouthwash and nasal spray in reducing the risk of cross-infection of COVID-19 among the dentists and their assistants.[1] The evidence used was based on in vitro data of PVP-I's virucidal activity against coronaviruses such as SARS-CoV and MERS-CoV. Here, we demonstrate in vitro virucidal activity of an oral PVP-I product against SARS-CoV-2, the virus causing COVID-19.

BETADINE Gargle and Mouth Wash in two concentrations, undiluted (PVP-I 1% w/v) and at a 1:2 dilution (PVP-I 0.5% w/v) was tested for virucidal activity (≥4 log10 reduction in viral titres) against SARS-CoV-2 in both clean (0.3 g/l BSA) and dirty (3.0 g/l BSA + 3 mL/L human erythrocytes) conditions at time points of 15, 30 and 60 seconds in a BSL-3 laboratory of the Tropical Infectious Diseases Research and Education Center (TIDREC), University of Malaya, Malaysia. The SARS-CoV-2 was isolated and propagated in Vero-E6 cells in TIDREC. The cytotoxicity of the product to the Vero-E6 cells was evaluated and taken into account when performing the kill time assay. Virus kill time assay was performed based on the established EN14476 methodology.[2] Virus titres were calculated as 50% tissue culture infectious dose (TCID50/mL) using the Spearman-Karber method.[2] The study demonstrated that undiluted PVP-I achieved >5 log10 reduction in the virus titres at 15, 30 and 60 seconds treatment exposure under both clean and dirty conditions. In contrast, when PVP-I was tested at 1:2 dilution a >4 log10 kill at 15 seconds and >5 log10 kill at 30 and 60 seconds in comparison to control was seen in both clean and dirty.

Dental practice poses a potential risk of COVID-19 cross-infection among patients, dentists and their assistants through direct exposure to saliva and indirect contact through contaminated instruments.[3] Several associations, including the Australian Dental Association, have recommended using a preprocedural mouthwash with products such as povidone iodine.[4] In our study, we present direct evidence of the virucidal activity of PVP-I gargle and against SARS-CoV-2 in just 15 seconds. In today's scenario, PVP-I gargle and mouthwash could be an adjuvant to PPEs in reducing the risk of COVID-19 transmission in healthcare practices, especially when oral interventions are warranted, such as in dental practice.