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

Introduction With the introduction of Paxlovid™ (a combination of nirmatrelvir and ritonavir) in Canada, a clinical gap was identified for patients with cancer. These patients often take multiple medications with complex mechanisms that can interact with Paxlovid™ (due to ritonavir's potent and irreversible inhibition of CYP3A4 by ritonavir). When this pharmacist-led drug interaction assessment service was started in February 2022, drug interaction databases did not include Paxlovid™. Also, complete medication records for patients receiving treatment within cancer clinics were not readily accessible to healthcare professionals in the community. To address this gap, BC Cancer established a real-time pharmacist-led drug interaction service to support prescribers across British Columbia (BC), Canada. Methods Between February 2022 and June 2023, a total of 575 consultation requests were received from across British Columbia. These requests came from a diverse group of healthcare providers, including oncologists, family physicians, nurse practitioners, nurses, and pharmacists, as well as from patients. Data was collected and analyzed from these consults and chart reviews to identify trends and characterize the utilization of this unique service. Results Analysis showed that the program supported hundreds of patients with cancer across British Columbia, regardless of their geographical location, age, sex, comorbidities, or primary cancer diagnosis. The findings also demonstrate that this pharmacist-led drug interaction service was equitably accessible to patients across the province. Conclusions This oncology pharmacist-led initiative supported the prescribing clinicians in the safe and effective use of Paxlovid™ in patients with cancer, minimizing disruption to their cancer therapy. This paper describes the programs’ development, implementation, and provides insights into the key challenges and successes encountered during its province-wide rollout.