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Covid 19

Paxlovid: First Oral pill for Covid-19 approved by FDA

  • April 18, 2022
  • 3 mins read

The U.S. Food and Drug Administration or FDA has recently approved the most awaited first oral antiviral pill for Covid-19 infection, Pfizer’s Paxlovid, for emergency use authorization. This medicine is a combination of nirmatrelvir and ritonavir antiviral drugs (protease inhibitors). It will treat mild to moderate coronavirus infection in adults and pediatric patients weighing at least 40 kgs (80 pounds). Healthcare professionals recommended it in the patients with positive results of direct SARS-CoV-2 testing and at high risk for progression to severe COVID-19, including hospitalization or death. This medicine is prescribed medicine, and healthcare providers can prescribe this medicine to only patients diagnosed with Covid-19.

Paxlovid is not authorized for the pre-exposure or post-exposure prevention of COVID-19 or initiation of treatment in those requiring hospitalization due to severe or critical COVID-19. It is not to be misunderstood as a substitute for vaccination. Paxlovid’s active ingredient, nirmatrelvir, will inhibit a SARS-CoV-2 protein from stopping the virus from replicating, and ritonavir will slow down nirmatrelvir’s breakdown to help it remain in the body for a longer period at higher concentrations. The Paxlovid has potential risks and benefits in treating Covid-19 infection. There is no other alternative medication for Paxlovid. 

According to the data from clinical trials like EPIC-HR, a randomized, double-blind, placebo-controlled clinical trial studying Paxlovid to treat non-hospitalized symptomatic adults with a laboratory-confirmed diagnosis of SARS-CoV-2 infection. In the clinical study analysis, 1,039 patients had received Paxlovid, and 1,046 patients had received a placebo. Among these patients, 0.8% who received Paxlovid were hospitalized or died during 28 days of follow-up compared to 6% of the placebo patients. 

The common side effects of Paxlovid are impaired sense of taste, diarrhoea, high blood pressure and muscle aches, and there are severe side effects of this medicine like liver-related problems. Before administering this medicine to the patient, the healthcare provider should know about the medical health and the medications taken by the patient previously. One should take the dosage according to the prescription prescribed by the healthcare professionals. 

Encapsulated information about Paxlovid

Paxlovid is a combination medicine of Nirmatrelvir Ritonavir. Nirmatrelvir is a peptidomimetic inhibitor of the SARS-CoV-2 main protease (Mpro), also referred to as 3C-like protease (3CLpro) or nsp5 protease. Inhibition of SARS-CoV-2 Mpro renders it incapable of processing polyprotein precursors, preventing viral replication. 

Ritonavir is an HIV-1 protease inhibitor but is not active against SARS-CoV-2 Mpro. Ritonavir inhibits the CYP3A-mediated metabolism of nirmatrelvir, resulting in increased plasma concentrations of nirmatrelvir. 

Paxlovid is nirmatrelvir tablets co-packaged with ritonavir tablets. The tablets contain Nirmatrelvir as an active ingredient, and the inactive ingredients are colloidal silicon dioxide, croscarmellose sodium, lactose monohydrate, microcrystalline cellulose, and sodium stearyl fumarate. Ritonavir is another active ingredient, with inactive ingredients anhydrous dibasic calcium phosphate, colloidal silicon dioxide, copovidone, sodium stearyl fumarate, and sorbitan monolaurate. 

Dosage and Administration

One should administer both Nirmatrelvir and Ritonavir tablets together. Failure to correctly co-administer nirmatrelvir with Ritonavir may result in plasma levels of nirmatrelvir that are insufficient to achieve the desired therapeutic effect.

The general dosage of Paxlovid is 300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet) with all three tablets taken together orally twice a day for 5 days. One should initiate the 5-day treatment course of Paxlovid soon after a diagnosis of COVID-19 has been made and within 5 days of symptom onset.

One could take these medicines with or without food. The tablets should be swallowed whole and not chewed, broken, or crushed.  


Before Paxlovid came into consideration, an oral pill named Molnupiravir by Merck came into being as the first oral pill for Covid-19 infection. Still, after the FDA’s analysis and research conducted by many renowned scientists, the mechanism of Molnupiravir medicine became a subject of stress. The Food and Drug Administration (FDA) narrowly approved this medicine on 30 Nov 2021, keeping in mind the surge of the Omicron variant of SARS Covid-19 for emergency use only. Molnupiravir has the potential to work against many viral infections. However, according to the FDA guidelines, the mechanism of Molnupiravi could be dangerous for humans as it could alter the genetic material DNA along with the genetic material of viruses (RNA). And thus, Molnupiravir shows low efficacy and safety in the treatment of Covid-19 infection.