What is Paxlovid?

Dr Rimsha Qasim 03:18 PM, 16 Sep, 2022
What is Paxlovid?

Known as the world’s fastest drug development project, Paxlovid is the first oral antiviral pill for COVID-19 infection granted an emergency use authorization (EUA) by the Food and Drug Administration (FDA) in December 2021. It is prescribed for anyone aged 12 years or older, weighing at least 88 pounds, and at a high risk of severe disease with underlying conditions such as cancer, diabetes, obesity, or others. It is a pill that is taken at home to prevent hospitalization. The reassuring factor is that it is expected to also work against the new Omicron variant. Pfizer developed the drug, and it had an 89% reduction in hospitalization rate and death, prompting it to get approved quickly. In April 2022, United Nations made a deal with the manufacturers to supply this drug to low- and middle-income countries.

How does it work?

It’s an antiviral therapy drug containing two medicines combined, nirmatrelvir and Ritonavir. When SARS-CoV-2 infects a cell, it hijacks the cellular apparatus to replicate itself, allowing it to continue spreading inside the body. Nirmatrelvir is the active component in Paxlovid. It targets an enzyme called Mpro, which plays a vital role in its ability to reproduce. What Nirmatrelvir does is that it prevents Mpro from manufacturing the proteins that SARS-CoV-2 needs to replicate. As a result, the COVID-19 virus cannot infect other cells once it enters the body. The other drug component is called Ritonavir, which works as a boosting agent. It decreases the rate at which Nirmatrelvir is metabolized in the liver, resulting in higher concentrations in the body and a more extended drug clearance period. It gives Nirmatrelvir the boost to fight infections. Ritonavir has been previously used in HIV antiviral therapies.

How to take Paxlovid?

The two medicines are taken together two times as 3 pills of two 50 mg tablets of nirmatrelvir and one 100 mg tablet of Ritonavir daily for 5 days. It only works within the first 5 days of the onset of symptoms. The entire course is approximately 30 pills. This tablet will not work if the patient has been fighting the virus for more than a week.

o Nirmatrelvir is an oval, pink tablet.

o Ritonavir is a white or off-white tablet.

Who should not take Paxlovid?

It is not prescribed to patients who are allergic to nirmatrelvir, Ritonavir, or any of the ingredients in Paxlovid. Drug interactions and previous medical history are essential to record before prescribing the drug. Dose adjustments are required in mild to moderate kidney disease. Any allergic reaction or clinical manifestation should be immediately reported to the healthcare provider.

Paxlovid rebound

Reports of a “rebound” of COVID-19 infection in some people within 2- 8 days of completing the five-day course of Paxlovid are coming out, though the patients are mostly asymptomatic. In the clinical trial, this rebound happened in an insignificant number of patients and those taking a placebo. The most high-profile example is President Biden, who developed an asymptomatic COVID-19 infection after testing negative. Isolation, in this case, is still crucial.

Dr Rimsha Qasim

The author is contributing writer at Medical News Pakistan and can be reached at



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