The U.S. Food and Drug Administration ( FDA ) has issued an emergency use authorization ( EUA ) for Pfizer’s Paxlovid ( Nirmatrelvir tablets and Ritonavir tablets, co-packaged for oral use ) for the treatment of mild-to-moderate coronavirus disease ( COVID-19 ) in adults and pediatric patients ( 12 years of age and older weighing at least 40 kilograms or about 88 pounds ) 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.
Paxlovid 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.
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.
The FDA has approved one vaccine and authorized others to prevent COVID-19 and serious clinical outcomes associated with a COVID-19 infection, including hospitalization and death.
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.
Paxlovid is administered as three tablets ( two tablets of Nirmatrelvir and one tablet of Ritonavir ) taken together orally twice daily for five days, for a total of 30 tablets.
Paxlovid is not authorized for use for longer than five consecutive days.
The primary data supporting this EUA for Paxlovid are from EPIC-HR, a randomized, double-blind, placebo-controlled clinical trial studying Paxlovid for the treatment of non-hospitalized symptomatic adults with a laboratory confirmed diagnosis of SARS-CoV-2 infection.
Patients were adults 18 years of age and older with a prespecified risk factor for progression to severe disease or were 60 years and older regardless of prespecified chronic medical conditions.
All patients had not received a COVID-19 vaccine and had not been previously infected with COVID-19.
The main outcome measured in the trial was the proportion of people who were hospitalized due to COVID-19 or died due to any cause during 28 days of follow-up.
Paxlovid has significantly reduced the proportion of people with COVID-19 related hospitalization or death from any cause by 88% compared to placebo among patients treated within five days of symptom onset and who did not receive COVID-19 therapeutic monoclonal antibody treatment.
In this analysis, 1,039 patients had received Paxlovid, and 1,046 patients had received placebo and among these patients, 0.8% who received Paxlovid were hospitalized or died during 28 days of follow-up compared to 6% of the patients who received placebo.
The safety and effectiveness of Paxlovid for the treatment of COVID-19 continue to be evaluated.
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.
Because Paxlovid works, in part, by inhibiting a group of enzymes that break down certain drugs, Paxlovid is contraindicated with certain drugs that are highly dependent on those enzymes for metabolism and for which elevated concentrations of certain drugs are associated with serious and/or life-threatening reactions.
Paxlovid is also contraindicated with drugs that, conversely, strongly induce those same enzymes, leading to the faster breakdown of Nirmatrelvir or Ritonavir, as reduced concentrations of Nirmatrelvir or Ritonavir may be associated with potentially losing virologic response and developing viral resistance.
Paxlovid cannot be started immediately after discontinuing such medications because the effects of those medications remain after discontinuation.
Paxlovid is not recommended in patients with severe kidney or severe liver impairment. In patients with moderate renal impairment, a reduced Paxlovid dose is needed.
Patients with kidney or liver problems should discuss with their healthcare provider whether Paxlovid is right for them. ( Xagena )
Source: FDA, 2021