Following authorization by Health Canada, Pfizer has begun distribution of its COVID-19 oral antiviral pill, PAXLOVID.
Ontario Minister of Health, Christine Elliot, announced on Twitter that Ontario received its first shipment of the Paxlovid courses on January 21st. The pill is initially being prioritized for high-risk sites and individuals, including 400 courses that are on their way to Ontario’s First Nations communities. 120,000 treatments are scheduled for distribution nationwide between February and March and will be available by prescription.
Given that Paxlovid will be distributed on a rolling basis, access for high-risk populations will be prioritized. High-risk groups include those in a moderate-to-severe immunocompromised state regardless of vaccination status, the elderly, those in long-term care, those 60 years or older living in underserved and remote communities, or those in indigenous communities whose vaccination status is not up to date.
PAXLOVID, the brand name for the COVID-19 pill, is said to treat mild-to-moderate COVID-19 in adults. According to Pfizer, PAXLOVID will cut hospitalization and death rates by nearly 90 per cent.
Brett Barrett, UW’s very own clinical lecturer at the School of Pharmacy and a licensed pharmacist, shared valuable information on PAXLOVID and similar antiviral medications. While many believe PAXLOVID will be the cure for COVID-19, Barrett noted that it is not a miracle remedy.
“The important thing to understand about antivirals is that, unlike antibiotics, they don’t kill the virus, they only prevent it from replicating. In acute infections like COVID-19, therefore, they need to be started as early in the infection as possible to get the most benefit. The more virus that has already been made, the less impact the antiviral is able to have,” he said. Barrett explained that once a patient has been admitted for severe COVID-19, PAXLOVID can no longer be used.
PAXLOVID contains a combination of nirmatrelvir and ritonavir. Nirmatrelvir is a protease inhibitor that blocks viral replication. Ritonavir is a metabolic inhibitor that is used to maintain the concentrations of nirmatrelvir at therapeutic levels. The recommended dosage is nirmatrelvir 300 mg with ritonavir 100 mg orally, twice daily for five days.
As explained by Barrett, in a clinical trial aimed at high-risk patients, PAXLOVID reduced the risk of hospitalization or death by 89 per cent compared to placebo in non-hospitalized adults with confirmed SARS-CoV-2 infection. This trial was a multinational, randomized, double-blind trial of adults with mild-to-moderate COVID-19 who were at high risk for poor outcomes.
They were randomized within five days of symptom onset, were unvaccinated, and had at least one risk factor for severe disease. A total of 2,246 participants were enrolled and 66 per cent started therapy within three days of symptom onset. In a separate study on PAXLOVID targeting standard-risk patients, little difference was shown from the placebo group.
Barrett shared a few caveats with PAXLOVID that should be acknowledged in addition to recognizing the urgency for interventions. Firstly, Health Canada has approved PAXLOVID on the basis of interim results made available by Pfizer that have yet to be published or peer-reviewed. Medications and interventions are usually only provided to the public once published, but the recent surge of COVID-19 has caused the pharmaceutical and medical industries to act hastily.
Secondly, since the symptoms of mild-to-moderate COVID-19 overlap with other viral upper respiratory tract infections, it is recommended that PAXLOVID be limited to patients who have had their infection confirmed by either PCR or rapid antigen tests. It is also imperative that PAXLOVID be administered as early as possible for COVID-19 patients. However, the number of steps involved before patients can receive PAXLOVID — from contacting a physician to getting test results back — threaten the timeliness of this critical window for treatment.
Finally, PAXLOVID has many known drug-drug interactions. Given that vulnerable populations are the primary target for PAXLOVID distribution, it must be administered carefully to avoid any harm.
Ultimately, it’s difficult to predict whether PAXLOVID will have the intended impact on the healthcare system. Due to an inadequate response to COVID-19, the current strain on the healthcare system is likely to remain for a long time.
Given the clinical trials, it is difficult to definitively conclude that symptoms and transmission will be reduced. The key is the time of delivery, therefore pharmacists, nurses and doctors alike must be diligent in their use of the medication. Antiviral drugs like remdesivir and sotrovimab have more data on their efficacy against COVID-19, therefore PAXLOVID’s success will soon be determined.
