Paxlovid: the long list of contraindicated medications

Health Canada approved Pfizer's COVID-19 antiviral medication, Paxlovid, on January 17, 2022. The new treatment must be prescribed with caution because of the many contraindications and potential drug-drug interactions. While Health Canada has concluded that the benefits of Paxlovid outweigh its risks, the director of the federal agency's Bureau of Medical Sciences, Dr. Marc Berthiaume, pointed out that Pfizer’s treatment “has the potential to interact with a number of other drugs, potentially decreasing its effectiveness or in some cases causing potentially serious effects.” In its decision summary, Health Canada states that these drug interactions “may result in clinically significant adverse reactions, potentially leading to severe, life-threatening, or fatal events, or loss of therapeutic effect of Paxlovid and possible development of viral resistance. Read: COVID-19 antiviral pill incoming as fifth wave's peak in sight for some provinces The agency lists medications that are contraindicated because of drug-drug interactions with Paxlovid: alfuzosin, used to treat benign prostatic hypertrophy amiodarone, bepridil*, dronedarone, flecainide, propafenone and quinidine, used to treat arrythmias apalutamide, used to treat prostate cancer astemizole* or terfenadine*, used to relieve allergy symptoms cisapride*, used to relieve certain stomach disorders colchicine, when used to treat gout in patients with kidney or liver problems 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 reduce cholesterol levels lurasidone and 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 (these drugs should not be taken with ritonavir) rivaroxaban, used as an anticoagulant salmeterol, used for asthma and chronic obstructive pulmonary disease St. John's wort (Hypericum perforatum), a herbal medicine used to treat depression triazolam and midazolam* (oral or injection), used to relieve anxiety and/or sleep disorders PDE5 inhibitors: vardenafil, used to treat erectile dysfunction, or sildenafil, when used to treat pulmonary arterial hypertension voriconazole, used as an antifungal agent venetoclax, at initiation of treatment and during the dose escalation period, used to treat chronic lymphocytic leukemia carbamazepine, phenobarbital and phenytoin, used as anticonvulsants (epilepsy) * Products that are no longer marketed in Canada. Read: Canadian trial: remdesivir reduces need for ventilation by half for COVID patients Health Canada also advises health professionals that the following products may also interact with Paxlovid: medications used to treat erectile dysfunction, like tadalafil medications used to treat pulmonary arterial hypertension, like bosentan or tadalafil medications used to lower blood cholesterol, such as atorvastatin and rosuvastatin certain medications that affect the immune system, such as cyclosporine, sirolimus and tacrolimus certain medications used to treat seasonal allergies and ear and eye infections, such as budesonide, dexamethasone, fluticasone propionate, prednisone and triamicinolone medications used to treat AIDS and AIDS-related infections, such as amprenavir, indinavir*, nelfinavir, saquinavir, didanosine*, rifabutin, tipranavir, delavirdine*, atazanavir, maraviroc, fosamprenavir, raltegravir, tenofovir and darunavir medications used to treat depression, such as trazodone, desipramine and bupropion certain medications for heart problems, such as calcium channel blockers, including diltiazem, nifedipine and verapamil medications used to regulate heart rhythm, such as systemic lidocaine and digoxin antifungals such as ketoconazole and itraconazole* morphine-like medications used to relieve severe pain, such as methadone and meperidine anticoagulants, such as warfarin some antibiotics, such as rifabutin and clarithromycin antibiotics used to treat tuberculosis, such as rifampin bronchodilators used to treat asthma, such as theophylline anti-cancer medications such as abemaciclib, dasatinib, encorafenib, ibrutinib, nilotinib, vincristine and vinblastine medications used to treat low blood platelet counts, such as fostamatinib some medications for heart rhythm disorders, such as mexiletine and disopyramide some anticonvulsants, such as clonazepam, divalproex, lamotrigine and ethosuximide certain narcotic analgesics, such as all forms of fentanyl, tramadol and propoxyphene quetiapine used to treat schizophrenia, bipolar disorder and major depressive disorder medications used to treat hepatitis C, such as simeprevir, glecaprevir/pibrentasvir or ombitasvir, paritaprevir and ritonavir with or without dasabuvir*; certain sedatives or medications used to treat anxiety, such as buspirone, clorazepate, diazepam, flurazepam and zolpidem stimulants, such as methamphetamine medications used to relieve pain associated with endometriosis, such as elagolix medications used to treat depression, such as amitriptyline, clomipramine, fluoxetine, imipramine, maprotiline*, nefazodone*, nortriptyline, paroxetine, sertraline, trimipramine medications used to treat nausea and vomiting, such as dronabinol*; medications used to treat pneumonia, such as atovaquone medications used for sedation and drugs used to help you sleep (hypnotics), such as estazolam medications used to reduce intraocular pressure, such as timolol medications used to reduce blood pressure, such as metoprolol medications used to treat HIV, such as efavirenz; medications used to prevent rejection of transplanted organs, such as everolimus and rapamycin medications used to treat certain mental or mood disorders, including schizophrenia and bipolar disorder, such as perphenazine, risperidone and thioridazine medications used as hormonal contraceptives containing ethinyl estradiol (the pill) * Products that are not or no longer marketed in Canada. Health Canada will continue to receive data from Pfizer, including further evaluation of the safety of Paxlovid in pregnant and breastfeeding women, Dr. Berthiaume said. Post-marketing safety reports and an updated risk assessment are also expected. Read: Health Canada safety review of drug used for rheumatoid arthritis finds heart and cancer risks This piece was translated from its original French and was first published in Profession Santé

Paxlovid: the long list of contraindicated medications

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