As drug interactions with Paxlovid are extremely common, Alice Tseng says pharmacist expertise is critical for drug to be safe and effective

Starting this week, community pharmacists across Ontario are able to prescribe the COVID-19 medication Paxlovid to patients at high-risk of serious outcomes. Alice Tseng, associate professor – status at the U of T’s Leslie Dan Faculty of Pharmacy and HIV pharmacotherapy specialist at Toronto General Hospital, says the change recognizes the important role that pharmacists play as medication experts.

“It makes a lot of sense for pharmacists to have this prescribing role.”

 “Pharmacists are accessible in the community, and they have the expertise in medication management and drug interactions that is needed with this drug,” says Tseng. “It makes a lot of sense for pharmacists to have this prescribing role.”

In early 2022, Health Canada approved Paxlovid, an oral medication to treat mild to moderate COVID-19 in patients who are at high risk of developing serious disease, including older adults and people who are immunocompromised. The drug is typically started within the first five days of symptoms and is being provided at no cost to patients.

Paxlovid includes two different medications: nirmatrelvir, an antiviral drug that stops the SARS-CoV-2 virus from replicating, and ritonavir, which slows the breakdown of nirmatrelvir in the body. Ritonavir’s activity is not limited to nirmatrelvir; in fact, it has been used for years in combination with other drugs to treat HIV and hepatitis C and is known to slow the breakdown and boost the levels of many drugs in the body, including drugs used for cancer, heart conditions and psychiatric disorders.

As an HIV specialist, Tseng has helped many patients with HIV manage drug interactions with ritonavir. When it started to be combined with antiviral drugs to treat COVID-19 as early as the spring of 2020, she was concerned about the possibility of drug interactions in patients. She wrote a brief about Paxlovid for the now-disbanded Ontario Science Table and began working with other pharmacists and physicians from different specialties to develop guidance for prescribers and pharmacists dispensing Paxlovid, available through the UHN Immunodeficiency Clinic website.

“The patients who need Paxlovid are those who are most at risk of severe outcomes, but these are people who are often taking drugs for other conditions,” says Tseng. “There can be significant interactions where concentrations of other medications can also be elevated, and that can place them at risk of side effects.”

In some cases, patients taking a particular drug are ineligible for Paxlovid treatment, while in other cases, it might be possible to pause or adjust a medication while the patient is on Paxlovid.

“Most of the drug interactions are manageable, but you want to make any decision about changing medication with the patient and their health care provider,” Tseng adds.

Increased access to Paxlovid aims to ease pressure on health care system

With pharmacists able to prescribe medications for minor ailments starting in January, the move to allow pharmacists to prescribe Paxlovid is part of a larger shift in the profession that aims to improve health care accessibility. For Paxlovid in particular, making it easier for patients to access the drug will help keep those at highest risk of serious illness out of the hospital ­– which has become even more important in recent weeks given the health care system is currently under strain from the increased hospitalizations due to COVID-19, influenza and RSV.

“All these changes together – prescribing Paxlovid, minor ailments prescribing, the expanded scope of practice – highlight what a big role pharmacists can play in our health care system,” says Tseng. “In so many aspects of the COVID-19 pandemic, pharmacists more than stepped up. We played a monumental role in providing care during the pandemic, and this change is one more piece of that role.”

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