Safety profile of nirmatrelvir-ritonavir: Evidence of adverse events due to drug-drug interactions.

Objective: The aim of the study was to evaluate the safety profile of nirmatrelvir-ritonavir (NMV-r) in real clinical practice and to analyze the clinical relevance of drug-drug interactions in the development of adverse events.

Methods: Observational, retrospective study in which safety data of patients treated with NMV-r between April and July 2022 in an outpatient setting were evaluated. The duration of follow-up was 28 days and the number of adverse reactions reported, as well as whether they were managed on an outpatient basis or required health care, and the presence of renal and hepatic function impairment were assessed. Concomitant treatment was reviewed, identifying theoretical drug-drug interactions (TDDIs) whose severity was defined using the Lexi-interact classification.

Results: The study included 146 patients, 82 (56,16%) were women, whose median age was 65 years (22-95). The number of TDDIs detected and maintained during treatment with NMV-r was 164, with the percentage of patients with at least one interaction being 62,33%. The median number of TDDIs per patient was 1 (0-5). At least 1 adverse event (AE) was reported in 18 patients (11,84%). Eleven AEs were potentially related to any TDDI. Seven patients required contact with hospital assistance for AE management. Eight patients had impaired renal function and 2 had impaired liver function at 28 days. The main groups of drugs implicated in the occurrence of an AE were oral anticoagulants and calcium antagonists.

Conclusions: Our results show a high number of TDDIs detected were detected between NMV-r and other drugs. This study provides greater knowledge of the drugs involved in such interactions and their potential relationship with the occurrence of adverse events.