Incidence of Drug Interactions Identified by Clinical Pharmacists in Veterans Initiating Treatment for Chronic Hepatitis C Infection

Background: Many direct-acting antivirals (DAAs) have drug-drug interactions (DDIs) with the potential to affect efficacy and safety. Objective: To describe the incidence and severity of DDIs with DAAs identified by the hepatitis C virus (HCV) clinical pharmacist within a Veterans Affairs health care system. Methods: This single-center, retrospective cohort study evaluated patients with HCV treated with DAA therapy. Primary end points included the total number of identified DDIs, percentage of patients with at least 1 DDI, mean number of DDIs per patient, and the number of DDIs by severity category. Additional end points included characterization of interacting drugs, clinical consequence of interaction, intervention recommended, acceptance rate of actionable recommendations, and achievement of sustained virological response 12 weeks after treatment (SVR12). Results: A total of 300 patients were included. There were 554 identified DDIs, and 80.3% of patients had at least 1 DDI, with an average of 1.85 DDIs per patient; 76% of the DDIs identified were categorized as either a potentially clinically significant or critical interaction. The most common DDIs involved acid suppression agents (20%). Patient monitoring was the most commonly recommended intervention (59%), followed by dose modification of the interacting medication (30%). There was no difference in SVR12 between patients with at least 1 DDI compared with those with no DDIs (94.8% vs 95.8%; P = 0.73). There were a total of 227 actionable recommendations, with an acceptance rate of 84.1%. Conclusions: This study suggests that DDIs are prevalent among patients treated with DAAs for HCV. A HCV clinical pharmacist can help optimize patient care by identifying DDIs and recommending interventions to providers.