4CPS-231 Analysis of drug interactions related to the initiation of nirmatrelvir/ritonavir in a geriatric population

<h3>Background and Importance</h3> Drug induced iatrogenesis causes approximately 130.000 hospitalisations and 10.000 deaths annually, with a higher incidence within the geriatric population, which often has multiple comorbidities and is polymedicated. The combination of nirmatrelvir/ritonavir (NR) is prescribed for non-oxygen-requiring SARS-CoV-2 infections at high-risk of progressing to severe forms. However, NR can cause drug interactions (DIs), as ritonavir is a potent inhibitor of cytochrome P450–3A4. <h3>Aim and Objectives</h3> This project aims to evaluate the proportion of NR prescriptions that led to pharmaceutical interventions (PIs) in a geriatric population. <h3>Material and Methods</h3> A retrospective, monocentric, observational study was conducted, examining patients treated with NR from 21 January 2022 (when early access was obtained), to 1 March 2024. Data were extracted from the prescription software Dxcare, and from the hospital pharmacy’s dispensing software history, Pharma, to analyse the types of PIs and their impact on prescriptions. <h3>Results</h3> A total of 121 patients (mean age 88 years, male/female ratio 31/88), with an average of two comorbidities, received NR. Out of the 65 patients with known vaccination status, 86% were vaccinated. Forty-nine prescriptions resulted in at least one PI, totalling 62 PIs, 50 (81%) of which led to the modification of prescriptions, for example, the interruption of treatment of drugs that should not be coadministered with NR, such as oral anticoagulants (n=11, 32%), and statins (n=16, 47%). Four types of PIs were identified: dosage modification (n=28, 45%), DI management (n=27, 44%), initiation proposal (n=2, 3%) and monitoring (n=5, 8%). Notably, some patients treated with NR were not eligible: 18.7% either had no comorbidities (n=10), had received oxygen therapy (n=1), or tested positive for SARS-CoV-2 more than 5 days prior (n=2). <h3>Conclusion and Relevance</h3> This study shows that NR prescriptions generated a significant amount of PIs, which were broadly accepted. However, this number is underestimated as some interventions were conducted orally and not recorded. This highlights the crucial role of pharmacists in ensuring treatment safety. Ultimately, appropriate prescription of NR is essential considering the high cost of the treatment. <h3>References and/or Acknowledgements</h3> <h3>Conflict of Interest</h3> No conflict of interest