Background: With the rise in off-season patterns of viral infections, approaches to prevent respiratory tract infections and reduce the risk of antibiotic resistance are required.

Aims: To determine the in vitro virucidal efficacy of antiseptic cetylpyridinium chloride (CPC) throat lozenges on coronavirus and influenza virus A.

Methods: Sugar-containing (SC) and sugar-free (SF) CPC lozenges (Dolo-Dobendan®) were tested with the DIN EN 14476:2019?10 suspension test. Tablets were diluted 80% and incubated with bovine coronavirus (S379 Reims) or influenza virus A (H1N1; Brisbane/59/2007) under clean (0.3g/L bovine serum albumin) or dirty (tripartite soil load according to OECD, to mimic saliva secretion) conditions. A 10-min exposure (equivalent to tablet oral dissolution time) was used to calculate viral titre (TCID50/ml), with a reduction ?4log10 (?99.99%) considered sufficient. For coronavirus, large volume plating (LVP) was used as ?4log10 was not possible due to cytotoxicity.

Results: For influenza, after 5mins SC CPC exhibited 98.52% efficacy in clean (1.83±0.58) and dirty (1.83±0.54) conditions, and for SF 4log10 (?99.99%) in clean (5.17±0.33) and dirty (4.00±0.00) conditions. Using LVP for coronavirus, after 10 mins SC CPC exhibited ?99.9% efficacy in clean (3.43±0.45) and 99.8% in dirty (2.66±0.47) conditions, and SF CPC exhibited ?99.99% efficacy in dirty (4.01±0.47) and 99.91% in clean (4.06±0.45) conditions.

Conclusion: CPC lozenges demonstrated in vitro virucidal efficacy against coronavirus and influenza virus, which is relevant for the treatment of viral mouth and throat infections, and may be used as a preventative oral hygiene measure to reduce viral transmission risk.