Impact of Clinical Pharmacists' Interventions on Medication Use and Direct Cost Savings in an Inpatient Medical Oncology Setting.

Introduction: There are limited studies evaluating the impact of clinical pharmacists' interventions (CPIs) and pharmacist-driven cost savings in the inpatient oncology settings. This study aimed to assess the clinical impact of CPIs and direct cost savings from deprescribing-related interventions in an inpatient oncology service. Methods: A retrospective study was conducted by assessing CPIs extracted from the pharmacy documentation system in the medical oncology service between January 2022 and December 2023. The clinical impact of these CPIs was evaluated through including interventions accepted by physicians and resulted in therapy changes, along with their significance levels. Direct cost savings were calculated for deprescribing interventions, including drug discontinuation and intravenous-to-oral (IV-PO) conversions, based on the cost saved per intervention over a 24-hour period. Results: During the study period, 9995 CPIs were identified, of which, 99.0% (n = 9887) were accepted by physicians and included in the analysis. The most frequent interventions were recommendations for drug additions/dose change (n = 3603, 36.4%), followed by drug discontinuations (n = 2886, 29.0%). Antimicrobials were the most frequently involved drug class (n = 4017, 40.7%). Significant CPIs that improved standard of care accounted for 7274 (73.6%) interventions, while very significant and extremely significant interventions were 2595 (26.3%) and 14 (0.14%), respectively. The overall direct cost savings from deprescribing were $102 710, with drug therapy discontinuations and IV-PO conversions contributing $99 305 and $3405, respectively. Conclusion: CPIs showed significant clinical and financial impact, with a high rate of accepted interventions resulting in therapy changes. Further prospective studies are required to analyze the clinical outcomes and indirect cost savings.