Background and Importance Nirmatrelvir/ritonavir (PAXLOVID) is a recently approved drug to prevent progression in high-risk COVID-19-infected patients.

Aim and Objectives To evaluate prescribing and dispensing of PAXLOVID and the proportion of patients with hospitalisation or death from any cause at 28 day.

Material and Methods Descriptive, retrospective, observational study carried out between May and August 2022 in a second-level hospital. All patients with PAXLOVID prescription were selected. Sources of information were: electronic medical records and the prescription programme. The Variables analysed were: sex, age, risk factors, indications, interactions, dispensation (yes/no) and final treatment received. Risk factors were evaluated with our country's drug regulatory agency (DRA) recommendations to assesed the indication. Efficacy was assessed by the proportion of patients admitted to hospital and 28-day mortality.

Results PAXLOVID was prescribed to 34 patients, 14 (41.2%) were women. The median age was 76.3 years old [RIQ 25.4]. Main indications for PAXLOVID were: to be undergoing treatment with myelotoxic chemotherapy (32.3%), corticosteroids or other immunosuppressants (29.4%); being over 80 years of age and presenting specific Risk factors (14.7%) and primary immunodeficiency (5.8%). 21 patients (61.8%) had some relevant interaction with their usual medication. The most frequent interactions were with statins (23.5%), analgesics (20.6%), oral anticoagulants (12%), antiarrhythmics (8.8%), antiplatelet drugs (5.8%), antidepressants (5.8%) and antidiarrhoeals (5.8%).

After Validatión by the Pharmacy Service, 11 patients (32.4%) did not receive PAXLOVID, 5 because they did not meet DRA criteria, 2 because their glomerular filtration rate was less than 30 ml/min and 4 because they had incompatible interactions. 4 patients finally received 3 days-remdesivir.

Among patients who received PAXLOVID, 82.26% received full doses, with 4 patients (11.76%) requiring adjustment for renal impairment. 3 patients (13%) were hospitalised in the first month, none died.

Conclusion and Relevance The main indications for which PAXLOVID was prescribed were patients undergoing chemotherapy and/or immunosuppressive treatments. Interactions with PAXLOVID were frequent and in some cases limited treatment. Validation by Pharmacy Service prevented a considerable number of patients from receiving PAXLOVID when it was no-indicated or when they had insurmountable interactions, also allowed patients to receive the dose adjusted for renal impairment. PAXLOVID was effective in avoiding hospital admission and mortality in the majority of patients.

Conflict of Interest No conflict of interest