Toronto 
Health Canada has approved Paxlovid, an antiviral pill by Pfizer for treating adults requiring hospitalization due to severe or critical COVID-19.
Credit: Pfizer Canada
The agency says Paxlovid should not be used to prevent COVID-19 and is not authorised for those under less than 18 years of age. It should not be used longer than five days and on those who are hospitalized due to severe or critical COVID-19.
Health Canada on the decision to approve the medicine states on the website, “Health Canada considers that the benefit-harm-uncertainty profile of Paxlovid in the treatment of mild-to-moderate COVID-19 in adult patients with positive results of direct SARS-CoV-2 viral testing, and who are at high risk for progression to severe COVID-19 is favourable under conditions of use described in the Paxlovid Product Monograph at this time; no safety and efficacy data were submitted for pediatric patients (12 years of age and older weighing at least 40 kg) and therefore, Paxlovid is not authorized for use in these patients.”
Paxlovid treatment consists 150 mg Nirmatrelvirand (pink tablet) and 100 mg Ritonavir (white tablet) tablets packaged together. Paxlovid is authorized to be administered twice-daily for five days. One carton contains five blister packs of Paxlovid providing all required doses for a full five-day treatment course.
According to Pfizer, Nirmatrelvir contains an inhibitor specifically designed to block the activity of the SARS-CoV-2 Mpro, an enzyme that the coronavirus needs to replicate.
Pfizer’s patient information sheet advises those who have the following conditions not to take Paxlovid:
- You are allergic to nirmatrelvir, ritonavir or to any of the other ingredients in PAXLOVID.
- You are taking any of the following medicines:
- alfuzosin, used to treat high blood pressure
- amiodarone, bepridil, dronedarone, flecainide, propafenone, quinidine, used to treat irregular heartbeats
- apalutamide, used for prostate cancer
- stemizole or terfenadine, used to relieve allergy symptoms
- cisapride, used to relieve certain stomach problems
- colchicine, when used in patients with kidney and/or liver problems, used to treat gout
- ergotamine, dihydroergotamine (used to treat headaches), ergonovine, methylergonovine (used after labour and delivery)
- fusidic acid, used as an antibiotic
- lovastatin, lomitapide or simvastatin, used to lower cholesterol
- lurasidone, pimozide, used to treat mental health problems
- neratinib, used to treat breast cancer
- ranolazine, used to treat chronic angina (chest pain)
- rifampin and saquinavir, used to treat tuberculosis, should not be used together with ritonavir
- rivaroxaban, used as an anticoagulant
- salmeterol, used for asthma and chronic obstructive pulmonary disease
- St. John’s Wort (Hypericum perforatum), an herbal product used to treat depression
- triazolam and midazolam (oral or injected), used to relieve anxiety and/or trouble sleeping
- PDE5 inhibitors vardenafil, used to treat erectile dysfunction, or sildenafil, used for the treatment of pulmonary arterial hypertension (PAH)
- voriconazole, used as an antifungal
- venetoclax during the dose initiation and during the ramp-up phase, used to treat chronic lymphocytic leukemia
- carbamazepine, phenobarbital, phenytoin used to treat seizures (epilepsy)
The government of Canada has signed an agreement with Pfizer to procure one million treatment courses of PAXLOVID in 2022.
