Patient‐Reported Adverse Drug Events on Nirmatrelvir–Ritonavir: A Prospective Observational Study of a Pharmacist‐Led Follow‐Up and Monitoring Service

Background There is a paucity of population‐based data on adherence and adverse drug events (ADEs) associated with the treatment of coronavirus disease 2019 (COVID‐19) with nirmatrelvir and ritonavir (NMV/r). We sought to contribute data on patient‐reported treatment adherence and ADEs with NMV/r using data collected by community pharmacists. Methods Data on patient‐reported NMV/r adherence and ADEs, the study outcomes, were collected by pharmacists through the Paxlovid Follow‐up (PAX‐F) service, with linkage to administrative data from the British Columbia (BC) Ministry of Health. The cohort study included individuals in BC prescribed NMV/r between January 31, 2022, and December 31, 2022. Pharmacists conducted phone assessments with patients or their caregivers after completion of NMV/r treatment. Responses were recorded in the PharmaNet database, a provincewide data network. Logistic regression was used to identify characteristics associated with the study outcomes. Results PAX‐F service was provided to 10 200 individuals. Median age was 72 years, and 56.4% were female. There were 87.6% of respondents ( n = 9034) who reported completing all 5 days of their NMV/r medication; 7351 individuals with a PAX‐F assessment (72.1%) were dispensed medications with a known interaction with NMV/r. 47.8% of respondents ( n = 4960) reported experiencing a total of 7439 ADEs, of which 1.5% of ADEs ( n = 115 in 79 individuals) were reported to have been managed at a hospital or emergency room. Female sex was associated with an increased risk of nonadherence to NMV/r compared with men (odds ratio [OR], 1.53; 95% confidence interval [CI], 1.41–1.68), and an increased risk of ADEs (OR, 1.32; 95% CI, 1.15–1.53). Nonvaccination was associated with nonadherence to NMV/r (OR, 3.05; 95% CI, 2.41–3.87), but not with reporting an ADE (OR, 1.04; 95% CI, 0.85–1.29). Conclusion Nearly half of NMV/r users in BC reported ADEs with treatment, suggesting that careful consideration of the risks and benefits of prescribing NMV/r is warranted.