Contraindications Due to Drug Interactions

PAXLOVID is contraindicated with drugs that are primarily metabolized by CYP3A and for which elevated concentrations are associated with serious and/or life-threatening reactions and drugs that are strong CYP3A inducers where significantly reduced nirmatrelvir or ritonavir plasma concentrations may be associated with the potential for loss of virologic response and possible resistance. There are certain other drugs for which concomitant use with PAXLOVID should be avoided and/or dose adjustment, interruption, or therapeutic monitoring is recommended.

Drugs listed in this section are a guide and not considered a comprehensive list of all drugs that may be contraindicated with PAXLOVID. The healthcare provider should consult other appropriate resources such as the prescribing information for the interacting drug for comprehensive information on dosing or monitoring with concomitant use of a strong CYP3A inhibitor like PAXLOVID [see Drug Interactions (7.3)]:

Drugs that are primarily metabolized by CYP3A for which elevated concentrations are associated with serious and/or life-threatening reactions [see Drug Interactions (7.3)]:

• Alpha₁-adrenoreceptor antagonist: alfuzosin
• Antianginal: ranolazine
• Antiarrhythmic: amiodarone, dronedarone, flecainide, propafenone, quinidine
• Anti-gout: colchicine (in patients with renal and/or hepatic impairment [see Table 1, Drug Interactions (7.3)])
• Antipsychotics: lurasidone, pimozide
• Benign prostatic hyperplasia agents: silodosin
• Cardiovascular agents: eplerenone, ivabradine
• Ergot derivatives: dihydroergotamine, ergotamine, methylergonovine
• HMG-CoA reductase inhibitors: lovastatin, simvastatin (these drugs can be temporarily discontinued to allow PAXLOVID use [see Table 1, Drug Interactions (7.3)])
• Immunosuppressants: voclosporin
• Microsomal triglyceride transfer protein inhibitor: lomitapide
• Migraine medications: eletriptan, ubrogepant
• Mineralocorticoid receptor antagonists: finerenone
• Opioid antagonists: naloxegol
• PDE5 inhibitor: sildenafil (Revatio®) when used for pulmonary arterial hypertension (PAH)
• Sedative/hypnotics: triazolam, oral midazolam
• Serotonin receptor 1A agonist/serotonin receptor 2A antagonist: flibanserin
• Vasopressin receptor antagonists: tolvaptan

Drugs that are strong CYP3A inducers where significantly reduced nirmatrelvir or ritonavir plasma concentrations may be associated with the potential for loss of virologic response and possible resistance. PAXLOVID cannot be started immediately after discontinuation of any of the following medications due to the delayed offset of the recently discontinued CYP3A inducer [see Drug Interactions (7.3)]:

• Anticancer drugs: apalutamide
• Anticonvulsant: carbamazepine, phenobarbital, primidone, phenytoin
• Antimycobacterials: rifampin
• Cystic fibrosis transmembrane conductance regulator potentiators: lumacaftor/ivacaftor
• Herbal products: St. John’s Wort (hypericum perforatum)

Risk of Serious Adverse Reactions Due to Drug Interactions

Initiation of PAXLOVID, which contains ritonavir, a strong CYP3A inhibitor, in patients receiving medications metabolized by CYP3A or initiation of medications metabolized by CYP3A in patients already receiving PAXLOVID, may increase plasma concentrations of medications metabolized by CYP3A.

Medications that induce CYP3A may decrease concentrations of PAXLOVID.

These interactions may lead to:

• Clinically significant adverse reactions, potentially leading to severe, life-threatening, or fatal events from greater exposures of concomitant medications.
• Loss of therapeutic effect of PAXLOVID and possible development of viral resistance.

Severe, life-threatening, and/or fatal adverse reactions due to drug interactions have been reported in patients treated with PAXLOVID. The most commonly reported concomitant medications resulting in serious adverse reactions were calcineurin inhibitors (e.g., tacrolimus, cyclosporine), followed by calcium channel blockers.

Prior to prescribing PAXLOVID, review all medications taken by the patient to assess potential drug-drug interactions and determine if concomitant medications require a dose adjustment, interruption, and/or additional monitoring (e.g., calcineurin inhibitors) [see Contraindications (4) and Drug Interactions (7)]. See Table 1 for clinically significant drug interactions, including contraindicated drugs. Drugs listed in Table 1 are a guide and not considered a comprehensive list of all possible drugs that may interact with PAXLOVID.

Consider the benefit of PAXLOVID treatment in reducing hospitalization and death, and whether the risk of potential drug-drug interactions for an individual patient can be appropriately managed [see Drug Interactions (7) and Clinical Studies (13)].

Potential for PAXLOVID™ (nirmatrelvir tablets; ritonavir tablets) to Affect Other Drugs

PAXLOVID (nirmatrelvir co-packaged with ritonavir) is a strong inhibitor of CYP3A, and an inhibitor of CYP2D6, P-gp and OATP1B1. Co-administration of PAXLOVID with drugs that are primarily metabolized by CYP3A and CYP2D6 or are transported by P-gp or OATP1B1 may result in increased plasma concentrations of such drugs and increase the risk of adverse events. Co-administration of PAXLOVID with drugs highly dependent on CYP3A for clearance and for which elevated plasma concentrations are associated with serious and/or life-threatening events is contraindicated [see Contraindications (4) and Drug Interactions (7.3) Table 1]. Co-administration with other CYP3A substrates may require a dose adjustment or additional monitoring as shown in Table 1.

Potential for Other Drugs to Affect PAXLOVID

Nirmatrelvir and ritonavir are CYP3A substrates; therefore, drugs that induce CYP3A may decrease nirmatrelvir and ritonavir plasma concentrations and reduce PAXLOVID therapeutic effect [see Contraindications (4) and Drug Interactions (7.3) Table 1].

Established and Other Potentially Significant Drug Interactions

Table 1 of PAXLOVID Product Insert provides a listing of clinically significant drug interactions, including contraindicated drugs. [see Contraindications (4)]. Drugs listed in Table 1 are a guide and not considered a comprehensive list of all possible drugs that may interact with PAXLOVID. The healthcare provider should consult other appropriate references resources such as the product label for the interacting drug for comprehensive information on dosing or monitoring with concomitant use of a strong CYP3A inhibitor such as ritonavir.

How to verify your tablets are authentic

PAXLOVID must be prescribed by a licensed healthcare provider and supplied by a government approved pharmacy or medical facility.

Authentic PAXLOVID, from Pfizer Inc., will include the Pfizer name on the label and will be packaged in 5 aluminum push-through blister cards. Individual doses are not for sale. PAXLOVID will be packaged in a rectangular carton. The carton has a colorless, glossy coating that contains a repeated pattern of the Pfizer name and logo all over, and these repeating features are seen in a contrasting matte finish.

PAXLOVID consists of tablets for a 5-day oral treatment regimen, with morning and evening doses.

Pfizer is committed to patient safety and ensuring that people have accurate information about the investigational drug PAXLOVID, including how it is accessed and administered. We are actively monitoring for fraudulent offers of illegitimate PAXLOVID to protect patients from products that might be dangerous and lead to serious and life-threatening harm.

If you suspect the product you have received may be counterfeit, visit www.pfizer.com.hk/en/connect-with-us

Reference: Paxlovid (Nirmatrelvir, Ritonavir) Prescribing Information. Pfizer Corporation Hong Kong Limited Version May 2023