The U.S. Food and Drug Administration authorized Pfizer’s Paxlovid (nirmatrelvir tablets and ritonavir tablets, co-packaged for oral use) for emergency use for the treatment of mild-to-moderate coronavirus disease in adults and children 12 years and older weighing at least 40 kilograms with positive results of direct SARS-CoV-2 testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death.

The drug is available by prescription only and should be initiated as soon as possible after diagnosis of COVID-19 and within five days of symptom onset, the FDA said.

EFFICACY

Pfizer's antiviral regimen, Paxlovid, was 89% effective in preventing hospitalizations and deaths in patients at high risk of severe illness, according to data from the company's clinical trial. Recent lab data suggests the drug retains its effectiveness against Omicron, Pfizer said.

DOSAGE AND ADMINISTRATION

PAXLOVID is nirmatrelvir tablets co-packaged with ritonavir tablets. Nirmatrelvir must be co administered with ritonavir.

·        Initiate PAXLOVID treatment as soon as possible after diagnosis of COVID-19 and within 5 days of symptom onset.

·        Administer orally with or without food.

·        Dosage: 300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet), with all three tablets taken together twice daily for 5 days.

WARNINGS

Paxlovid is not authorized for the pre-exposure or post-exposure prevention of COVID-19 or for initiation of treatment in those requiring hospitalization due to severe or critical COVID-19. Paxlovid is not a substitute for vaccination in individuals for whom COVID-19 vaccination and a booster dose are recommended.

Paxlovid consists of nirmatrelvir, which inhibits a SARS-CoV-2 protein to stop the virus from replicating, and ritonavir, which slows down nirmatrelvir’s breakdown to help it remain in the body for a longer period at higher concentrations.

SIDE EFFECTS

Possible side effects of Paxlovid include impaired sense of taste, diarrhea, high blood pressure and muscle aches. Using Paxlovid at the same time as certain other drugs may result in potentially significant drug interactions. Using Paxlovid in people with uncontrolled or undiagnosed HIV-1 infection may lead to HIV-1 drug resistance. Ritonavir may cause liver damage, so caution should be exercised when giving Paxlovid to patients with preexisting liver diseases, liver enzyme abnormalities or liver inflammation.  

CONTRAINDICATIONS

Paxlovid is not recommended in patients with severe kidney or severe liver impairment.

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