Pfizer’s Paxlovid First Oral Antiviral for Covid-19

Paxlovid (Nirmatrelvir/Ritonavir) is an investigational SARS-CoV-2 protease inhibitor antiviral therapy that received an emergency use authorization (EUA) by the Food and Drug Administration (FDA). The agency confirmed that Paxlovid is authorized for the treatment of mild-to-moderate COVID-19 in adults and pediatric patients who are at an increased risk of progressing to severe illness. The dosage recommended for this drug is three pills (one of ritonavir and two of nirmatrelvir) twice a day for a total of 30 pills.

They added that Paxlovid is only available by a valid prescription. It must be indicated for use within 5 days of the onset of symptoms. Plus, it must not be used for more than 5 days in any case. 

Majorly, the problem of Paxlovid is that there is insufficient production of the drug by its manufacturer Pfizer. The company revealed only 180,000 treatment courses of Paxlovid are available by now. Another 80 million are expected by the end of the year 2022. Pfizer has claimed about 10 million courses of this drug.

Experts suggest that other companies must join Pfizer in the manufacturing of Paxlovid so that the supplies remain smooth for the rest of the world. 

As per the results of the EPIC-HR trial, Paxlovid was found to cut deaths and severe conditions (including hospitalizations) by approximately 90% in patients who are at high risk. Moreover, the trial included 2,200 people and no deaths were noted. The common side effects of Paxlovid (Nirmatrelvir/Ritonavir) are muscle pain, loss of taste, high blood pressure, and diarrhea. Also, ritonavir can lead to serious conditions like liver damage or failure in patients who already have any liver disease or inflammation.

Nirmatrelvir, one of the tablets of Paxlovid, inhibits a cysteine residue in the SARS-CoV-2 3C-like protease (3CLPRO). This cysteine is required for the activity of SARS-3CLPRO CoV-2's and maybe other coronaviruses. Polyproteins 1a and 1ab are cleaved by the 3CLPRO, commonly known as the major protease or non-structural protein 5. The 3CLPRO, a papain-like (PL) cysteine protease, and 14 additional nonstructural proteins are all found in these polyproteins. Nonstructural proteins (including proteases) cannot be released to complete their activities if the 3CLPRO is not active, which inhibits viral propagation.

Paxlovid can cause severe interactions with other drugs associated with life-threatening conditions and regimens that produce the same enzymes that either Nirmatrelvir or Ritonavir inhibit. This regimen is not indicated for use in patients who have been suffering from liver or kidney impairment. 

Paxlovid is not recommended for the prevention of coronavirus illness before or after exposure. Furthermore, it is not a replacement for any COVID-19 immunizations. It's also not a good idea to start therapy in people who need to be admitted to the hospital owing to the severity of their infection.

Paxlovid (Nirmatrelvir/Ritonavir) can show interactions with medicines like sildenafil, mexiletine, vorapaxar, clozapine, disopyramide, phenobarbital, rifapentine, amiodarone, carbamazepine, clopidogrel, flibanserin, lurasidone, tadalafil, dofetilide, colchicine, lumateperone, apalutamide, bosentan, cisapride, iradine, and rifampin.


paxlovid, antiviral, covid-19, nirmatrelvir, ritonavir