A Cross-Sectional Study Comparing the Frequency of Drug Interactions After Adding Simeprevir- or Sofosbuvir-Containing Therapy to Medication Profiles of Hepatitis C Monoinfected Patients

INTRODUCTION: This study compares the expected occurrence of contraindicated drug–drug interactions (XDDIs) when simeprevir (SIM)- or sofosbuvir (SOF)-containing therapy is added to medication profiles of patients with hepatitis C (HCV) monoinfection to quantify, in relative terms, the population-based risk of XDDIs. Second, this study identified the predictors of XDDIs when HCV therapies are added to medication profiles. METHODS: A cross-sectional study was performed among Veterans’ Affairs patients. Inclusion criteria were: (1) age ≥18 years, (2) HCV infection, and (3) availability of a medication list. Patients with human immunodeficiency virus were excluded. Demographics, comorbidities, year of HCV diagnosis, and most recent medication list were collected from medical records. The primary outcome was the presence of XDDIs involving HCV therapy and the medications in the patient’s home medication list after the addition of either SIM- or SOF-containing regimens. To define XDDIs, Lexi-Interact drug interaction software was used. RESULTS: 4,251 patients were included. The prevalence of XDDIs involving SIM- or SOF-containing therapy were 12.6% and 4.7% (p < 0.001), respectively. In multivariable analyses examining the predictors of XDDIs involving SIM-containing therapy, the only medication-related predictor was use of ≥6 home medications (odds ratio OR 4.58, 95% confidence interval CI 3.54–5.20, p < 0.001). Similarly, use of ≥6 home medications was also the only variable associated with an increased probability of XDDI involving SOF-containing therapy (OR 3.83, 95% CI 2.57–5.70, p < 0.001). CONCLUSIONS: Sofosbuvir-containing therapy had a lower frequency of XDDIs than SIM-containing therapy. Polypharmacy with various classes of home medications predicted XDDIs involving SIM- or SOF-containing therapy. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s40121-015-0058-x) contains supplementary material, which is available to authorized users.