123 CMAAO CORONA FACTS and MYTH BUSTER: Mouth Rinse
Dr K K Aggarwal
947: Can oral rinses help stop the spread of COVID-19?
The SARS-CoV-2 virus is surrounded by a lipid envelope. Inserted into this bio-membrame are the spike glycoproteins required for infection. The membrane is amenable to disruption. To interfere with the lipid envelope is a well-known virucidal strategy against many coronaviruses. Salivary glands and throat are major sources of coronavirus replication. Furthermore, a high viral load in the mouth may contribute to the spread of disease in early stages of infection.
One such strategy is to use oral rinses that target the lipid envelope around SARS-CoV-2.
A review of more than 100 articles says some oral rinses may help curb the spread of SARS-CoV-2. Dampening down the levels of shed virus, even transiently, may have an impact on transmission of disease to vulnerable people or to healthcare professionals who routine work in the upper airway, such as ear, nose, and throat surgeons, anesthetists, and dentists. The review was published online May 14 in Function.
Studies have led to a consensus view that enveloped viruses, including SARS-CoV-2, are highly sensitive to 60% to 70% ethanol, which causes almost immediate inactivation.
1. With respect to ethanol, most studies have investigated the utility of higher concentrations of the compound. Few have examined the lower concentrations commonly found in commercially available mouthwashes. The small amount of research that has been conducted with lower ethanol concentrations has been promising. Two such trials, both conducted in vitro, yielded positive outcomes in relation to virus denaturation.
2. In 2007, a study concluded that 20% ethanol completely inactivated three enveloped viruses – sindbis, herpes simplex–1, and vaccinia. Another study published 10 years later showed that a 30-second exposure to a dilution containing 34% ethanol completely prevented coronavirus replication.
3. In 1995, researchers tested 26.9% ethanol plus essential oils against herpes, influenza, rotavirus, and adenovirus in vitro. Both herpes and influenza (which are enveloped) were significantly affected, whereas adenovirus and rotavirus (which are not enveloped) were not. This led the investigators to speculate that the oral rinse may alter the viral lipid envelope.
4. A 2010 unpublished follow-up study by the same group showed that a 30-second in vitro exposure to 21.6% ethanol with essential oils led to a more than 99.99% reduction of infectivity of H1N1 influenza.
5. These studies "provide proof-of-concept that mouthwashes containing essential oils with 21-27% ethanol can inactivate enveloped viruses, both in the lab and in humans, with the likely mechanism being damage to the lipid envelope,"
6. Chlorhexidine has been shown in vitro to reduce the viral concentration of enveloped viruses. Given that chlorhexidine formulations can retain their oral antimicrobial activity for up to 12 hours, the researchers note that combining them with ethanol may prove useful for reducing viral load over longer periods.
7. Povidone-iodine has also been the subject of a few human studies, which have shown that repeated gargling can reduce incidence of both bacterial and viral infection.
8. Rinsing with chlorinated water or hypertonic saline is another option and has borne fruit in a pilot study from Japan.
9. Hydrogen peroxide, which causes oxygen free radical–induced disruption of lipid membranes. Previous studies have shown that coronavirus 229E and other enveloped viruses are inactivated at hydrogen peroxide concentrations of approximately 0.5%. Although hydrogen peroxide concentrations greater than 5% can damage soft and hard tissues, little damage has been reported in the 1% to 3% concentration range commonly used in mouthwashes for teeth whitening.
10. Quaternary ammonium compounds are widely used microbicidal agents that interfere with protein or lipid components on the cell surface. One such compound is cetylpyridinium chloride, which has recently been shown to be active in vitro and in vivo against influenza through direct attack on the viral envelope.
Research should answer several questions, including the following:
• Can viral load in the oropharynx be reduced through 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 induce antiviral activity and reduce infectivity of SARS-CoV-2?
Stephen J. Challacombe, PhD, King's College London, United Kingdom.
In a review published earlier this year, Challacombe and colleagues assessed current evidence and concluded that povidone-iodine stands the best chance of reducing cross-infection.
The risk to healthcare workers is so high that there's every justification for going ahead and using it.
He also recommends 1.5% hydrogen peroxide ― even though it is not known whether it is inactivated in the presence of other organic matter.
Chlorhexidine has been subject to less research, though its virucidal properties make it an attractive possibility in this context.
Published online May 14, 2020. Abstract, Medscape
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