Anti-COVID Mouthwash: Spit, Don’t Swallow?

A complex treatment featuring povidone iodine mouthwash had some impact on viral titers in patients with COVID-19 versus controls, but with one notable side effect, a small French randomized trial found.

There was a larger mean relative difference in viral titers between baseline and day 1 in patients in the intervention group (75%, 95% CI 43%-95%) versus controls (32%, 95% CI 10%-65%), but confidence intervals were wide, and use of the intervention had “no influence on changes of viral quantification over time,” reported Olivier Mimoz, MD, PhD, of University Hospital of Poitiers in France, and colleagues.

Moreover, 42% of patients exposed to the mouthwash experienced thyroid dysfunction, which resolved when treatment was stopped, the authors wrote in a JAMA Otolaryngology — Head & Neck Surgery research letter.

They said their data called for larger trials to “confirm the benefit of [povidone iodine] in limiting the excretion and resulting human-to-human transmission of SARS-CoV-2,” but at lower concentrations to “minimize adverse effects.”

Researchers noted that in vitro studies where povidone iodine mouthwash in concentrations as low as 0.5% inactivated SARS-CoV-2 in a mere 15 seconds, and decided to test these theories in the real world.

They examined 24 adult outpatients testing “highly positive” for SARS-CoV-2 (defined as cycle threshold greater than or equal to 20) via reverse transcriptase polymerase chain reaction (RT-PCR) in the previous 48 hours. Patients were swabbed for viral quantification at baseline. Those with a history of thyroid disease were excluded.

While 12 were assigned to a group with no intervention, the remaining 12 were assigned to an intervention involving mouthwash, nasal spray, and ointment massaged into their nasal passages. They had four successive mouthwashes and gargles of 25 mL of “1% aqueous [povidone iodine] solution each,” followed by a 2.5-mL dose of nasal pulverization into each nostril while sniffing, and one application on each nasal mucosa of 10% povidone iodide ointment massaged into each nostril to help spread the ointment.

Patients performed this intervention four times a day for 5 days, and were followed up on day 1, and every 2 days until day 7 to assess viral quantification and safety of the decolonization.

Overall, intervention patients were younger than controls (median age 33 vs 57, respectively), and there were only four men in each group. All patients but one had a negative viral titer by day 3.

Examining safety, patients in the intervention group experienced “unpleasant nasal tingling,” and a jump in thyroid-stimulating hormone after 5 days, which exceeded the upper limit of normal in five patients. However, all patients returned to baseline values 7 to 12 days later, and there was no modification of thyroid hormone (T3 or T4) or creatinine levels.