According to NBC News, the Food and Drug Administration (FDA) has approved Pfizer’s Paxlovid, the first pills to transform the fight against viruses to treat mild-to-moderate Covid-19 patients as young as 12. However, either drug in the antiviral cocktail can cause severe or life-threatening interactions in combination with widely used drugs, including statins, blood thinners, and some antidepressants medications. The FDA explicitly advises persons with severe renal or liver illness not to take Paxlovid.

Two antiviral nirmatrelvir and one ritonavir, a medication that has long been used as a booster in HIV regimens, make up the Paxlovid cocktail. Ritonavir inhibits CYP3A, a key liver enzyme involved in the metabolism of numerous medications, including nirmatrelvir. Ritonavir reduces the body’s breakdown of the active antiviral in Paxlovid therapy, allowing it to stay at therapeutic levels for longer.

The main issue is that when Paxlovid is coupled with other medications metabolized by the CYP3A enzyme, the ritonavir component could increase the toxicity of the co-administered pharmaceuticals.

Complicating matters, the drugs with the potential for interactions are widely prescribed to people most at risk from Covid because of other medical issues.

Medications include, but are not limited to: blood thinners; antiepileptic drugs; medicine for irregular heartbeat, high blood pressure, and high cholesterol; antidepressants and anti-anxiety drugs; immunosuppressive drugs; steroids (including inhalers); HIV treatments; and drugs to treat erectile dysfunction.

The FDA has released a complete list of medicines that potentially interact negatively with ritonavir in the Paxlovid fact sheet, including those that should not be used with Covid antiviral treatments.

According to NBC News, Peter Anderson, a professor of pharmaceutical science at the University of Colorado Anschutz Medical Campus, medications with the potential for interactions are commonly recommended to COVID patients. “Other of these potential interactions are not trivial, and some pairs of interactions must be avoided altogether,” he added of other health concerns. “Some are fairly controlled, but some I will have to be extremely careful with.’

According to pharmacists, many drug interactions are manageable and should not prohibit most people from taking Paxlovid.

“Pharmacists are the specialists who help identify if there is a substantial connection and come up with solutions,” said Emily Zadvorny, executive director of the Colorado Association of Pharmacists.

Anderson advises that anyone seeking Paxlovid, which must be given within five days of the onset of symptoms, inform their prescribers and pharmacists of all prescriptions and supplements they are taking, as well as any over-the-counter supplements.

Jason Gallagher, a clinical pharmacist specialist in infectious illnesses at Temple University Hospital in Philadelphia, said, “For most medications, five days of interactions isn’t a significant concern.”

According to Anderson, some medicines, such as some statins, are probably safe to stop using while on Covid therapy. It may be preferable, for example, to keep certain blood thinners but reduce their dosage. Paxlovid interacts with some heart rhythm medicines.

Despite concerns regarding Paxlovid’s interaction with other prescription medications, doctors are optimistic about the drug’s potential.

Paxlovid, according to Anderson, is a “breakthrough medication.” “By offering many patients with an effective Covid treatment during the pandemic, this might make a huge difference.”

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