Four months ago, the U.S. Food and Drug Administration (FDA) authorized the first oral antiviral drug to treat COVID-19. Pfizer developed the treatment in pill form under the name Paxlovid, which consists of co-packaged nirmatrelvir and ritonavir tablets. The nirmatrelvir tablets can stop COVID-19 replication by inhibiting its protein, while the ritonavir tablets can keep the nirmatrelvir concentrations in the body in the therapeutic range by hindering its degradation. Experts believe that Paxlovid is effective against the latest COVID-19 variants, Delta and Omicron, because it attacks the virus life cycle stopping its replication rather than merely triggering our bodies to generate antibodies. The treatment involves taking two nirmatrelvir tablets and one ritonavir tablet together twice daily for five days.
Paxlovid is mostly used to treat mild to moderate COVID-19 cases in adults and children 12 years and older. It is not a substitute for vaccination, is not designed to prevent COVID-19, for cases requiring hospitalization due to severe COVID-19, or for those who are asymptomatic. In addition, it should be used with caution in patients with pre-existing liver and kidney diseases, liver enzyme abnormalities, or liver inflammation. Some possible side effects of this medication include an impaired sense of taste, diarrhea, high blood pressure, and muscle aches.
A second drug, Molnupiravir, developed by Merck, was authorized by the FDA a day after the authorization of Paxlovid. It is taken as four tablets twice a day. Both drugs have effectively reduced hospitalization and death due to COVID-19 if taken within days of the onset of symptoms. However, trials showed that Paxlovid is significantly more effective than Molnupiravir, reducing the risk of hospitalization and death in high-risk unvaccinated people by 88% compared to 30% with Molnupiravir.
The side effects of Molnupiravir are like those of Paxlovid, but it is not authorized for anyone under 18 years old because it may negatively impact bone and cartilage growth and should not be administered to pregnant women because it can lead to birth defects. In addition to these two drugs, the FDA cleared an intravenous antiviral medication called Veklury from Gilead Sciences, mostly administered at clinics.
References:
- Food and Drug Administration (FDA) (2021). Coronavirus (COVID-19) Update: FDA Authorizes First Oral Antiviral for Treatment of COVID-19. https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-first-oralantiviral-treatment-covid-19
- Knvul Sheikh, The New York Times (2022), New Antiviral Pills Help Treat Covid. Here’s How to Get Them. https://www.nytimes.com/explain/2022/03/21/well/covid-antiviral-pills
- Dennis Thompson, WebMD (2021). The New COVID Antiviral Pills: What You Need to Know. https://www.webmd.com/lung/news/20211229/the-new-covid-antiviral-pills-what-you-need-to-know#1
Assistant Professor - Environmental Health and Safety Program
College of Health Sciences
Abu Dhabi University