Disclaimer: This article is for informational purposes only and does not constitute medical advice. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a physician or other qualified health provider with any questions you may have regarding a medical condition.
Overview
Paxlovid® is a combination antiviral medication authorized in Canada.
Paxlovid® is a fixed-dose combination of two antiviral agents: nirmatrelvir and ritonavir. Nirmatrelvir inhibits a viral protease enzyme essential for viral replication, while ritonavir acts as a pharmacokinetic enhancer by inhibiting cytochrome P450 3A4 metabolism, increasing nirmatrelvir levels. This combination is formulated as oral tablets. Currently, Paxlovid® is the sole brand marketed in Canada containing this combination, with no generic equivalents or competing Canadian brands using the same active ingredients.
Available as oral tablets combining nirmatrelvir and ritonavir.
In Canada, Paxlovid® is supplied as two types of oral tablets packaged together: nirmatrelvir 150 mg tablets and ritonavir 100 mg tablets. The treatment course contains blister packs with a total of 30 tablets per package, designed to be taken orally. No other dosage forms such as liquids or injectables are currently authorized.
Follow prescribed dosing, usually twice daily with food.
How Paxlovid® Works
Paxlovid® blocks viral protease to prevent viral replication.
The active component nirmatrelvir targets and inhibits the SARS-CoV-2 main protease enzyme (Mpro), crucial for processing viral polyproteins required for replication. By blocking this protease, nirmatrelvir interferes with viral replication inside host cells. Ritonavir, although originally developed as an HIV protease inhibitor, in this combination primarily inhibits CYP3A4 enzymes in the liver, slowing nirmatrelvir metabolism and increasing its plasma concentration and effectiveness.
Dosage Instructions of Paxlovid®
Paxlovid® tablets are intended for oral use, typically taken twice daily approximately 12 hours apart, with or without food, but preferably with food to reduce potential stomach upset. Treatment duration and dosing must be strictly followed as prescribed by a healthcare professional. It is important not to alter dosage or stop treatment without consulting a doctor.
Storage Instructions
Store tablets at room temperature, away from moisture and heat. Paxlovid® tablets should be stored at controlled room temperature, typically between 15°C and 30°C, protected from light, moisture, and heat. Keep out of reach of children and do not use after the expiry date indicated on the packaging.
Side Effects of Paxlovid®
Usually mild; some serious reactions reported rarely.
Common side effects reported with Paxlovid® include altered taste (dysgeusia), diarrhea, high blood pressure, and muscle aches. Serious adverse reactions are rare but may include allergic reactions or liver enzyme abnormalities. Patients should report any severe or unusual symptoms to their healthcare provider immediately.
Important Safety Information About Paxlovid®
Use caution with liver, kidney issues; consult healthcare providers.
Health Canada advises caution when prescribing Paxlovid® to patients with moderate to severe kidney or liver impairment. The medication may not be suitable for individuals with certain pre-existing conditions or those taking medications with interactions. It is essential to inform healthcare providers of all current medications and medical history before starting Paxlovid®.
Drug Interactions
Avoid drugs metabolized by CYP3A4 or affecting heart rhythm.
Paxlovid® has significant interactions due to ritonavir's inhibition of CYP3A4 enzymes. Concomitant use with certain drugs such as some antiarrhythmics, statins, sedatives, and others metabolized by CYP3A4 may lead to serious adverse effects. Patients must disclose all medications and supplements to their healthcare provider to avoid harmful interactions.
Key Takeaways
- 1• Paxlovid® contains nirmatrelvir and ritonavir tablets for oral use.
- 2• Nirmatrelvir inhibits viral protease; ritonavir boosts drug levels.
- 3• Available only by prescription in Canada.
- 4• Store at room temperature, away from moisture and heat.
- 5• Possible side effects include altered taste and diarrhea.
- 6• Significant drug interactions require medical supervision.