Background and Importance The COVID-19 pandemic has highlighted the important role that hospital pharmacists play in improving pharmacotherapy outcomes. Paxlovid^® (Nirmatrelvir/ritonavir) was recently granted an Emergency Use Authorisation for the treatment of mild to moderate COVID-19. However, the use of Paxlovid^® with certain other drugs in high-risk patients may result in potentially significant drug-drug interactions (DDI) and adverse drug events (ADE).

Aim and Objectives To assess the impact of a comprehensive pharmaceutical care program (CPCP) focusing on the prevention of DDI and ADE, initiated in a hospital pharmacy for patients with mild to moderate COVID-19 treated with Paxlovid^®.

Material and Methods Design: Quasi-experimental study performed between 1 May and 31 July 2022. Pharmacists were responsible for proposing COVID-19 local guidelines to physicians, monitoring adherence to guidelines, managing DDI and ADE, providing patient education, and evaluating health outcomes. A telephone consultation was carried out 10 days after the end of Paxlovid^® treatment.

Potential DDI were detected according to Lexi-Comp^® and Liverpool COVID-19 databases. Paxlovid-related ADE reported were graded according to Common Terminology Criteria for Adverse Events, version 4.

Results 140 patients (60.7% outpatients) initiated Paxlovid^® and were enrolled in the CPCP. Adherence to local guidelines for the use of Paxlovid^® was 100%.

Overall, 232 DDI were detected in 111 (79.3%) patients, 142 (61.2%) of which required specific management (34.5% discontinuation of the concomitant drug and 65.5% dose adjustment).

Pharmacists made 267 interventions that led to the prevention of 177 ADE (1.3/patient), 96 (54.2%) of which were grade G-H (NCC MERP classification).

At day 10, 96 ADEs were reported in 42 patients (26.1% of which were grade ≥3), being dysgeusia and diarrhoea the most common. Premature discontinuation of Paxlovid^® due to ADEs was necessary in 4 (2.8%) patients.

Conclusion and Relevance The implementation of a CPCP developed by hospital pharmacists for patients treated with Paxlovid^® was an effective approach for monitoring adherence to guidelines, managing DDI, providing patient education, and evaluating safety outcomes. Paxlovid^® showed an acceptable safety profile.

Conflict of Interest No conflict of interest.