Development of a pharmacist-led drug interaction assessment service for patients with cancer diagnosed with mild to moderate COVID-19 infection requiring outpatient treatment.

This article focuses on the development and implementation of a pharmacist-led drug interaction assessment service at BC Cancer in British Columbia, Canada, designed to support safe use of Paxlovid™ (a combination of nirmatrelvir and ritonavir) in patients with cancer diagnosed with mild to moderate COVID-19. Due to ritonavir’s potent inhibition of the CYP3A4 enzyme and the complexity of cancer patients’ medication regimens, this service addressed critical gaps in drug interaction information and access to complete medication records. Between February 2022 and June 2023, the program received 575 consultation requests from diverse healthcare providers and patients across BC, providing timely, individualized assessments that facilitated safe COVID-19 antiviral therapy while minimizing disruption to cancer treatment. The service demonstrated equitable access across geographic regions, cancer types, and patient demographics, highlighting the important role of oncology pharmacists in managing complex drug interactions during public health emergencies. The article also discusses challenges encountered, such as initial lack of Paxlovid™ data in interaction databases and incomplete data collection, and offers insights for future large-scale pharmacist-led initiatives.