Frequency, type and severity of drug-related problems and pharmacist interventions in Paxlovid® prescribing: a descriptive analysis.

Background: Paxlovid® (nirmatrelvir and ritonavir) is the only licensed oral antiviral for COVID-19. Ritonavir is a potent inhibitor of cytochrome P450 enzymes causing numerous drug-drug interactions (DDIs).

Aim: To describe the frequency, type, and severity of detected drug related problems (DRPs) associated with Paxlovid®.

Method: This study involved a retrospective quantitative analysis including all patients prescribed Paxlovid® at a public hospital in Vienna, Austria. Data were collected from the patients' records by a clinical pharmacist. A customised, piloted data collection form was used. A sample of data was checked for consistency by an independent clinical pharmacist. Any DDI and severity classification was recorded using an established interaction checker tool. Dosage adjustments due to renal impairment were recorded.

Results: One hundred twenty-two of 140 patients (87.1%) required interventions to prevent DRPs. Pharmacists' intervention at dispensing was needed in 63.6% (n = 89) of cases. In 3 (2.1%) patients, Paxlovid® was prescribed despite being contraindicated due to severe renal impairment. The most common were DDIs (n = 80; 57.1%). Renal impairment and DDIs were noted in 24.3% (n = 34) of cases. A total of 313 DDIs were recorded in 114 (81.4%) patients, with severe interactions in 24 (17%) patients.

Conclusion: Pharmacists' involvement in prescribing highly interacting drugs such as Paxlovid® is essential to enhance patient safety.