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