The drug Paxlovid against Covid-19, manufactured by Pfizer, is the first oral antiviral treatment for COVID-19 to make headlines. The Food and Medicine Administration (FDA) granted the drug an emergency use authorization (EUA) in December for anyone aged 12 and up who weighs at least 88 pounds, and Pfizer recently began Phase 2 and 3 trials in children and teens aged 6 to 17.

Paxlovid is an antiviral drug that can be taken at home to potentially prevent high-risk individuals from becoming unwell enough to require hospitalization. If you test positive for the coronavirus (and your doctor issues you a prescription), you can take medications at home to reduce your chances of having to travel to the hospital.

What is the drug Paxlovid?

Paxlovid is made up of two drugs: nirmatrelvir, which stops the virus from replicating by inhibiting a SARS-CoV-2 protein, and ritonavir, which slows down the breakdown of nirmatrelvir and allows it to stay in the body for longer at greater concentrations. Paxlovid is given as a combination of three pills (two nirmatrelvir tablets and one ritonavir tablet) taken orally twice daily for five days, for a total of 30 tablets. Paxlovid is not recommended for use for more than five days in a row.

What are the possible side effects of Paxlovid?

Paxlovid can cause a loss of taste, diarrhea, increased blood pressure, and muscle aches, among other things. Paxlovid should not be taken with some other medications because it may cause serious drug interactions.

Who should not take Paxlovid?

Paxlovid should be used with caution in patients who have preexisting liver disorders, abnormal liver enzymes, or liver inflammation since ritonavir can induce liver damage.

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 because it works in part by inhibiting a group of enzymes that break down certain drugs. Paxlovid is also contraindicated with drugs that, on the other hand, strongly induce those same enzymes, resulting in faster nirmatrelvir or ritonavir breakdown, as lower nirmatrelvir or ritonavir concentrations have been linked to a loss of virologic response and the development of viral resistance. Because the effects of these medications last after they are stopped, Paxlovid cannot be begun right away after they have been stopped.

Paxlovid is not indicated for people who have significant kidney or liver problems. Paxlovid must be taken at a lower dose in patients with mild renal impairment. Patients with renal or liver disorders should explore whether Paxlovid is right for them with their doctor.

Is there any other danger?

There are numerous unpublished case reports now describing problems when the so-called antiviral treatment is used to treat COVID-19 patients by both physicians and patients.

Many people who tested positive for SARS-CoV-2 and were symptomatic claimed that after five days of therapy with Paxlovid, their symptoms were decreased or completely gone, and they tested negative, but then tested positive again a few days later, with symptoms emerging again.

According to doctors in the United States, the United Kingdom, and even China, their diseases worsened in some cases, requiring hospitalization.

Patients who tested positive for SARS-CoV-2 had lower viral loads after being treated with Paxlovid at first, but these viral loads reverted back to higher values on days 6 to 8 after initial treatment, according to two health centers in the United States, one in California and the other in Massachusetts (both have requested anonymity for now).

Interestingly, while testing negative via nasal PCR and experiencing symptom relief upon discharge, one patient from California showed viral persistence 58 days later via serological assays.

Given the number of such cases that have been reported unofficially by various physicians, a thorough investigation is urgently required.

Many reasons could be at play, such as Paxlovid not being an efficient antiviral, after all, leaving the potential for viral persistence difficulties, or new SARS-CoV-2 variants acquiring drug resistance to Paxlovid.

In any case, a thorough investigation by impartial researchers would help clarify the air on these oddities.

Image Credit: Getty

You were reading: How well Pfizer’s Paxlovid protects you against COVID-19 – updated with a new side effect