Background and Importance Paxlovid® is indicated for the treatment of COVID-19 in adults who do not require supplemental oxygen and who are at increased risk for progressing to severe COVID-19. The Spanish Drug Agency published prioritisation criteria for it access. Paxlovid® has significant drug interactions, mainly due to ritonavir. Hospital pharmacists must validate the prescription, carrying out a thorough review of the patient‘s medical history to check its suitability, as well as the concomitant medication to avoid interactions.

Aim and Objectives Analyse the use of Paxlovid^® in Huesca and Sector-1 of Zaragoza (Aragon, Spain) in early months post-authorisation.

Material and Methods All Paxlovid’s prescriptions from April to September 2022 were reviewed. The following variables were collected: gender, age, vaccination schedule, prioritised high-risk criteria and renal function. All concomitant medication was reviewed for drug interactions using a protocol created by Coordination Unit for the Rational Drug Use of Aragon. The observations made to the prescribing physician by the hospital pharmacist were recorded.

Results 40 requests were received. 5 were prescription errors. 29 (82.9%) were accepted and 6 (17.1%) rejected. Median age (years, interquartile-range q1-q3) was 52.2 (45.6–65.3), 57.1% were male. Vaccination status was complete primary vaccination with booster-dose (62.8%) followed by complete vaccination (25.7%) and incomplete vaccination (11.5%). As high-risk criteria prioritised, 91.4% belonged to group composed by immunocompromised persons. 91.4% had renal function >60ml/min. Only in 3 cases (8.6%) the prescribing physician indicated the patient had potential drug interactions.

All patients had concomitant medication, median of 8 drugs (4–10). 60% had any potential interaction, with serious drug interactions in 42.9% of them. Drugs with potential serious interactions were statins (5/11); benzodiazepines (2/11) and antithrombotic agents (2/11).

44.8% prescriptions were accepted with recommendations to modify or temporary stop some of the patient‘s usual treatment. 80% of the rejected cases were due to serious drug interactions.

Conclusion and Relevance In the use of Paxlovid®, the role of hospital pharmacists was crucial, as drug interactions were detected in 60% of patients and were serious in 42.9% of them, leading to recommendations for adjustments in patients‘ drug therapy in almost half of the cases, with potentially serious drug interactions being the main reason to not dispense Paxlovid®.

Conflict of Interest No conflict of interest