Comparing drug interaction frequencies of various hepatitis C treatment regimens among monoinfected patients

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Introduction and ObjectivesFour regimens are recommended for treating hepatitis C (HCV) genotype 1 infection. Study aims were to (1) compare frequencies of contraindicated drug interactions (XDDIs) when each HCV regimen is added to medication profiles of HCV-monoinfected patients, (2) quantify the proportion of patients with XDDIs to all four regimens and (3) determine covariates independently associated with having a XDDI to all four regimens. Materials and methodsA cross-sectional study was performed within Upstate New York Veterans Healthcare Administration. Inclusion criteria: (1) age ≥18 years, (2) HCV monoinfection and (3) available medication list. Data extracted were: demographics, comorbidities, and medication list. Primary outcome was XDDIs involving patient's home medications and each HCV regimen. University of Liverpool drug interaction website was used to define XDDIs. Two-way comparisons of regimens were performed using McNemar's test where p<0.0083 was considered statistically significant. Multivariate regression analyses were performed to determine predictors. ResultsOf the 4047 subjects, mean±standard deviation age was 59.8±7.6. Median (interquartile range) number of medications used was 7 [4–11]. Frequencies of XDDIs after the addition of each regimen ranged from 2.8% to 17.8% and were mostly statistically different from one another. There were 95 (2.3%) patients with XDDIs to all four regimens. Predictors of having XDDIs to all four regimens were ≥6 medications and HCV infection ≥10 years. ConclusionThe frequencies of XDDIs varied between HCV regimens. Number of medications and duration of HCV infection were predictors of having XDDIs to all four regimens.