B.C.'s top doctor says a new antiviral COVID-19 treatment may not be used for all individuals who are at a high risk of developing severe illness due to potential adverse interactions with medications.
On Jan. 17, Health Canada authorized the combination of two antiviral drugs, nirmatrelvir and ritonavir (brand name PAXLOVIDTM), to treat adults with mild to moderate COVID-19 who are at high risk of progressing to serious disease, including hospitalization or death.
The treatment is the first approved antiviral treatment for a coronavirus infection that may be administered at home instead of in a hospital and is intended for use within five days of symptom onset. Taken early, the drug prevents a more serious illness.
Provincial Health Officer Dr. Bonnie Henry told reporters on Jan. 18 that the treatment is meant for people over the age of 70, clinically extremely vulnerable, immune-compromised, and for younger people who have additional medical conditions and don't have the protection of vaccines.
But in a briefing on Tuesday (Feb. 1), Henry stated that the antiviral treatment has "conditional recommendations" and may not be appropriate for some individuals who are at high risk of developing a severe illness because of the medications they are on.
"This is a very challenging medication combination," she explained. "Many of the people who would potentially benefit from the antiviral medication may have a serious interaction with the treatment."
While every medication has risks and benefits, the health officer noted that the new antiviral combination has "important contraindications" and "drug interactions," which makes it different from other common antiviral treatments, such as Tamiflu.
Public health teams familiar with using antiviral drugs, particularly ritonavir—a protease inhibitor that is part of a combination of drugs also used for treating people with HIV—will start offering Paxlovid to people who are at the highest risk of developing severe illness by reaching out to them through a "proactive process" of monitoring lab data, Henry said.
The province has a limited supply of Paxlovid—about 4,000 treatment courses the medication—and will use a "heat map" of people who are most at risk based on things like underlying illness, one or two conditions, vaccination status and age to determine who will have access to it.
"There's still much that we need to learn [about Paxlovid] and what the side effects and the risks and benefits are," she noted. "And most importantly, it is used once somebody has been infected and is at risk of having severe enough illness to need hospitalization."
While Paxlovid is a tool in the management of COVID-19, Henry added that the most crucial step in preventing illness is getting vaccinated.
Paxlovid is an oral antiviral treatment for COVID-19, consisting of a combination of two medications that must be taken together. The first drug, nirmatrelvir, blocks an enzyme that the SARS-CoV-2 virus needs to reproduce. The second, ritonavir, slows down how fast nirmatrelvir breaks down so it can do its job for longer.
With files from the Canadian Press
