Povidone – Iodine
Povidone – Iodine (PVP-I) is a widely used iodine complex carried in a polyvinylpyrrolidone carrier that was developed in the 1950s and is available as a surgical skin prep agent and as a mouthwash.14 It has demonstrated both antibacterial and antiviral activity in past studies.14 While studies on virucidal activity of PVP-I have not yet been performed specifically on SARS-CoV-2, there have been numerous in-vitro studies demonstrating its effectiveness against multiple viruses including related coronaviruses. A 1997 study compared PVP-I to other antiseptics in inactivating a broad range of both enveloped and non-enveloped viruses (adeno-, mumps, rota-, polio-, coxsackie-, rhino-, herpes simplex, rubella, measles, influenza and human immunodeficiency viruses) and demonstrated PVP-I to have the broadest spectrum of antiviral activity among agents tested.15 Kariwa et al. tested several different commercially available PVP-I formulations against SARS-CoV-1 viral samples (responsible for the severe acute respiratory syndrome (SARS) epidemic) and found that the viral infectivity was reduced to below detectable levels within 2 minutes of application.16 In an industry sponsored study, Eggers et al carried out in-vitro tests of PVP-I solutions (1% to 7.5%) against MERS-CoV (responsible for the Middle East respiratory syndrome (MERS) epidemic) and found that the viral titre reduction of >99.99% within 15 seconds of application.17 A subsequent study examined a diluted PVP-I (0.23%) formulation against SARS-CoV-1, MERS-CoV, and Influenza A (H1N1) applied for 15 seconds and again found a >99.99% reduction of viral titres.18 Despite ample in-vitro studies, there are few clinical studies of PVP-I specifically against viruses. Still, in a small prospective Japanese study of school aged children, it was found that cohorts who were encouraged to used PVP-I gargle had significantly lower rates of absences from school due to the common cold and influenza.19
From a safety perspective, it has been tolerated for use in the upper airway as has been demonstrated in numerous human studies. In the oral cavity and oropharynx it has been used safely at a range of doses from 1% to 10% for oropharyngeal infection prophylaxis, mucositis and prevention of ventilator associated pneumonia.20–24Commercial over-the-counter oral mouthrinse formulations are typically of 1% PVP-I. Though there is some degree of mucosal absorption, even long term oral utilization has not been shown to cause thyroid dysfunction.25 It has also been utilized in the sinonasal mucosa at lower concentrations (0.08%) in the treatment of recalcitrant chronic rhinosinusitis without evidence of thyroid dysfunction, olfactory dysfunction or mucociliary clearance changes.26 Other studies have examined the effect of PVP-I in varying concentrations 0.5% to 5% on the sinonasal mucosa without detrimental effect to the nasal epithelium; however, one recent in-vitro study found that iodine preparations of 5% to 10% demonstrated some degree of ciliotoxicity.27–30Fortunately, PVP-I also exhibits the least ototoxicity of topical prep solutions and is safe to use as an ophthalmic prep agent (1% to 5%), which is relevant to head and neck procedure that involve or expose the skull base otologic or orbital apparatuses.31,32Unlike alcohol based preparations, it is not flammable which is relevant when using electrocautery in the airway.33