Chlorhexidine
Chlorhexidine is a disinfectant and antiseptic that has been in medical use since the 1950s. Oral rinse preparations are commonly used in dentistry to reduce plaque build-up and treat gingivitis, and studies show that it can reduce bacterial counts in saliva after as little as 30 seconds of exposure.34 There is more limited evidence showing its virucidal effects. In vitro studies in the 1970s first demonstrated activity of chlorhexidine gluconate against herpesvirus strains though not poliovirus or adenovirus.35 Later studies showed that chlorhexidine tends to have virucidal activity against enveloped viruses, though does not show the same effect against non-enveloped viruses. Bernstein et al showed virucidal activity of chlorhexidine gluconate against the enveloped viruses herpesvirus 1, cytomegalovirus, influenza A, parainfluenza, and hepatitis B after 5 minutes of exposure in vitro, with no activity against poliovirus.36 Baqui demonstrated this effect against human immunodeficiency virus 1 in vitro as well with two preparations of chlorhexidine as well as Listerine mouthwashes.37There are few studies examining chlorhexidine and coronaviruses, and those that do exist examine the effects of chlorhexidine on sterilization of inert surfaces rather than living tissue. These studies do, however, show sensitivity of coronavirus to chlorhexidine though only when used in combination with other compounds such as ethanol or cetrimide.38 In isolation, chlorhexidine has been found to be less effective against coronaviruses than PVP-I in both in-vitro studies and studies of disinfection of inanimate surfaces.15,39 Overall, there are limited data demonstrating the activity of chlorhexidine against coronaviruses and it is also associated with high levels of ototoxicity and can be flammable when utilized in commercial preparations that commonly include alcohol.31,33