Experts warn Pfizer’s COVID-19 pill may be risky with other medications

Pfizer’s new antiviral pills against Covid-19 may not be safe for everyone, experts have cautioned, adding that the new drug could be life-threatening when taken with other medications.

The US Food and Drug Administration (FDA) recently authorized Pfizer’s pill, Paxlovid, for emergency use in those with mild or moderate Covid-19 who are more likely to become seriously ill, including older people and those with underlying health conditions such as heart disease, cancer, or diabetes.

Paxlovid’s treatment is a combination of two pills consisting of the antiviral nirmatrelvir and one tablet of ritonavir, which should be taken over five days, which Pfizer said showed near 90 per cent efficacy in preventing hospitalisations and deaths in high-risk patients.

However, one of the two drugs in the antiviral cocktail could cause severe or life-threatening interactions with widely used medications, including statins, blood thinners and some antidepressants. And the FDA does not recommend Paxlovid for people with severe kidney or liver disease.

“Some of these potential interactions are not trivial, and some pairings have to be avoided altogether,” said Peter Anderson, a professor of pharmaceutical sciences at the University of Colorado Anschutz Medical Campus. “Some are probably easily managed. But some we’re going to have to be very careful about.”

In its fact sheet about Paxlovid, the FDA has published a detailed list of medications that may interact harmfully with ritonavir, including those that should not be paired with the Covid antivirals.

Many pharmacists have stressed that many of the drug interactions are manageable and that they should not preclude most people from taking Paxlovid.

“Pharmacists are highly trained experts in medication safety and monitoring and are an excellent source of information and advice about interactions between medications and also supplements and herbal products,” said Emily Zadvorny, a clinical pharmacist who is the executive director of the Colorado Pharmacists Society. “They will help determine if a significant interaction exists and devise solutions to mitigate the interaction if possible.”