Repurposing povidone-iodine to reduce the risk of SARS-CoV-2 infection and transmission: a narrative review

Abstract

Background: Accumulating data suggest antiviral effects of povidone-iodine against the Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. This narrative review aims to examine the antiviral mechanisms of povidone-iodine, efficacy of povidone-iodine against the SARS-CoV-2 virus, and safety of povidone-iodine to human epithelial cells and thyroid function.

Methods: We searched the electronic databases PubMed, Embase, Cochrane Library, ClinicalTrials.gov and World Health Organization's International Clinical Trials Registry Platform for articles containing the keywords "povidone-iodine", "SARS-CoV-2" and "COVID-19" from database inception till 3 June 2021.

Results: Despite in vitro data supporting the anti-SARS-CoV-2 effects of povidone-iodine, findings from clinical studies revealed differences in treatment response depending on study settings (healthy vs. hospitalized individuals), treatment target (nasal vs. oral vs. pharynx), method of administration (oral rinse vs. gargle vs. throat spray) and choice of samples used to measure study endpoints (nasopharyngeal vs. saliva). One large-scale clinical trial demonstrated reduction in the incidence of SARS-CoV-2 infection among participants who administered povidone-iodine 3 times daily during an active outbreak. Povidone-iodine is also used to disinfect the oro-pharyngeal space prior to dental or otolaryngology procedures. Although existing data suggest minimal impact of povidone-iodine on thyroid function, high-quality safety data are presently lacking.

Conclusions: Povidone-iodine application to the oropharyngeal space could complement existing non-pharmacological interventions to reduce SARS-CoV-2 infection especially in high exposure settings.Key messagesAccumulating data suggest antiviral effects of povidone-iodine against the SARS-CoV-2 virus.Findings from clinical studies reveal differences in treatment response depending on study settings, treatment target, method of administration and choice of samples used to measure study endpoints. One large-scale clinical trial observed reduction in the incidence of SARS-CoV-2 infection among participants who administered povidone-iodine 3 times daily during an active outbreak.Povidone-iodine application to the oropharyngeal space could complement existing non-pharmacological interventions to reduce SARS-CoV-2 infection especially in high exposure settings.

Keywords: Povidone-iodine; SARS-CoV-2; adverse effects; clinical studies; mechanisms.

Figure 1.

Effect of povidone-iodine on pathogen cellular structures. In aqueous solution, povidone-iodine dissolves to release free iodine, which then oxidizes membrane proteins on the surfaces of virus and bacterial pathogens [21].

Figure 2.

Povidone-iodine exerting its local anti-SARS-CoV-2 effects. The oropharynx is lined by stratified squamous non-keratinizing epithelium, with its underlying lamina propria and muscularis externa [98]. These epithelial cells contain ACE2 receptors, which are entry points for SARS-CoV-2 into humans tissues [90]. By coating the oropharynx, povidone-iodine blocks entry of the SARS-CoV-2 virus into host cells and prevents its spread to adjacent tissues.

Figure 3.

Methods of delivering povidone-iodine to the nasal and oropharyngeal spaces. (A) Nasal drops that are administered through the nostrils could deliver povidone-iodine to the nasal space and, to a lesser extent, the pharynx. (B) Oral gargle solution could cover the oral cavity and pharynx when correctly supervised. (C) Throat spray could direct administration of povidone-iodine to the pharynx. Due to the proximity of the pharynx and oesophagus, occasional swallowing of povidone-iodine could occur with the different methods of delivery.