947:  Can oral rinses help stop the spread of COVID-19?

The SARS-CoV-2 virus is surrounded by a lipid envelope. The spike glycoproteins are inserted into this bio-membrane. The membrane can be disrupted. A known virucidal strategy against several coronaviruses is to interfere with their lipid envelope. The coronavirus can replicate in the salivary glands and throat. Additionally, a high viral load in the mouth may contribute to the spread of disease in early stages of infection.

Oral rinses target the lipid envelope around SARS-CoV-2.

A review of over 100 articles suggests that some oral rinses may help check the spread of SARS-CoV-2. Even a transient decrease in the levels of the shed virus may affect the transmission of disease to vulnerable people or to healthcare professionals who routinely work in the upper airway, such as ear, nose, and throat surgeons, anesthetists, and dentists. The review was published online May 14 in Function.

Some studies have led to a consensus view that enveloped viruses, including the SARS-CoV-2, are highly sensitive to 60% to 70% ethanol, which can result in almost immediate inactivation.

1. In the context of ethanol, most studies have assessed the utility of higher concentrations while few have evaluated the lower concentrations commonly found in commercially available mouthwashes. The research conducted with lower ethanol concentrations has yielded promising results. Two such trials, both, in vitro, yielded positive outcomes in terms of virus denaturation.
2. A 2007 study revealed that 20% ethanol completely inactivated three enveloped viruses – sindbis, herpes simplex–1, and vaccinia. Another study published 10 years later revealed that exposure for 30 seconds to a dilution of 34% ethanol could prevent coronavirus replication.
3. In 1995, 26.9% ethanol plus essential oils were tested against herpes, influenza, rotavirus, and adenovirus in vitro. Herpes and influenza, both enveloped, were shown to be significantly affected, while adenovirus and rotavirus (not enveloped) were not. Investigators thus speculated that oral rinse may have the potential to alter the viral lipid envelope.
4. A 2010 follow-up study by the same investigators (unpublished) showed that a 30-second in vitro exposure to 21.6% ethanol with essential oils resulted in over 99.99% reduction of infectivity of H1N1 influenza.
5. These studies thus provide proof-of-concept that mouthwashes containing essential oils with 21-27% ethanol have the potential to inactivate enveloped viruses, both in the lab and in humans, likely by causing damage to the lipid envelope.
6. Chlorhexidine has been shown in vitro to decrease the viral concentration of enveloped viruses. Chlorhexidine formulations can retain their oral antimicrobial activity for up to 12 hours. The researchers note that combining them with ethanol may help in reducing viral load over longer periods.
7. Povidone-iodine has also been studied in a few human studies, which revealed that repeated gargling can limit the incidence of both bacterial and viral infection.
8. Rinsing with chlorinated water or hypertonic saline is also an option and has shown positive result in a pilot study from Japan.
9. Hydrogen peroxide tends to disrupt the lipid membranes induced by oxygen free radical. Previous studies revealed that coronavirus 229E and other enveloped viruses are inactivated at hydrogen peroxide concentrations of approximately 0.5%. Hydrogen peroxide concentrations >5% can damage soft and hard tissues, but little damage has been reported with the 1% to 3% concentration range which is commonly used in mouthwashes.
10. Quaternary ammonium compounds are microbicidal agents that interfere with protein or lipid components on the cell surface. Cetylpyridinium chloride is one such compound which is active in vitro and in vivo against influenza through direct attack on the viral envelope.

Research still needs to answer several questions, including the following:

• Can viral load in the oropharynx be decreased by means of oral rinsing?
• If yes, which oral rinse might be clinically effective?
• Would a combination of agents in lower amounts be better tolerated, reduce adverse effects, and remain effective?
• What combinations, contact times, and frequency of use might yield antiviral activity and reduce infectivity of SARS-CoV-2?

In a review published earlier this year, Stephen J. Challacombe, PhD, Kings College London, United Kingdom, and colleagues assessed current evidence and noted that povidone-iodine stands the best chance of reducing cross-infection.

Healthcare workers are at a high risk and it seems justified to go ahead and use it.

Challacombe also recommends 1.5% hydrogen peroxide despite the fact that it is not known whether it is inactivated in the presence of other organic matter.

Chlorhexidine has been studied less, though its virucidal properties make it an attractive possibility in this context.

[Medscape]

 Dr KK Aggarwal

President CMAAO