Pharmacovigilance of Drug-Drug Interactions with Nirmatrelvir/Ritonavir

Introduction: Nirmatrelvir/ritonavir (NMV/r) is approved in the United States (US) and more than 70 other countries for the treatment of mild to moderate COVID-19 in nonhospitalized adults at high risk for severe disease. Because ritonavir inhibits several drug metabolizing enzymes, potential drug-drug interactions (DDIs) between ritonavir and concomitant medications are an important consideration for prescribers. Here, we conducted a real-world analysis of data from Pfizer's global safety database regarding adverse events (AEs) reported during use of NMV/r concomitantly with potentially interacting drugs.

Methods: Data were extracted regarding DDI cases occurring from the start of NMV/r authorization through October 31, 2023. Results regarding concomitant treatment, specific AEs, and clinical outcomes are summarized. Overall NMV/r exposure was estimated based on packs of medication dispensed and was used to calculate reporting rates.

Results: Among 19,617,670 patients exposed globally to NMV/r, 966 cases of potential DDIs were reported. Of these, 594 occurred in the US against an estimated US exposure of 14,646,990 patients, representing a reporting rate of 0.004%. Globally and in the United States, 66.8% and 77.3% of cases, respectively, were nonserious. Simvastatin and tacrolimus were the most frequently reported drugs associated with potential DDIs, and the most frequently reported AE regarding a specific event or symptom was dysgeusia (altered sense of taste), an AE known to be associated with NMV/r.

Conclusions: Low reporting rates of DDIs support the potential for NMV/r treatment to be safely managed with careful use of available drug interaction resources to aid in risk mitigation.