gms | German Medical Science

Introduction: For treatment success in chronic diseases such as hypertension, adequate adherence to long-term pharmacotherapy is a prerequisite. The purpose of this study was to evaluate whether switching from brand name ramipril to a generic product after patent expiry may negatively affect patients’ refill compliance.

Methods: Claims data for ambulatory prescriptions within the statutory health insurance system covering more than 80% of German community pharmacies were evaluated. Patients were included if they filled a ramipril prescription (index) for either brand name or generic ramipril products between 11/2003 and 06/2004. Ramipril products with single active ingredient, fixed-dose combinations with diuretics, or both were considered. Patients had to be continuously treated with ramipril for at least 12 months before the index date (only brand name products on the market) as well as 12 months after the index date (allocation to generic or brand name group, respectively). Patients with a change from brand to generic product or vice versa during follow-up were excluded from the analyses, as were patients who could not be unequivocally allocated to characteristics of covariates.

Refill compliance was analysed by calculating the medication possession ratio (MPR), defined as days covered with medication divided by the number of days during the observation period. The MPR was calculated in two different ways: either assuming the WHO DDD (defined daily dose) as prescribed daily dose (MPR_DDD) or based on the number of days supplied with medication assuming that patients were prescribed one unit dose per day (MPR_UD).

Results: 221,881 patients were included, of which 142,690 and 79,191 were classified as brand name or generic therapy, respectively. Median MPR_DDD values for brand name or generic therapy were 1.04 and 1.35 (p<0.001), and median MPR_UD values were 0.95 and 0.96 (p<0.001). In a multivariate logistic regression model, the probability for non-compliance (MPR_UD <0.8) was marginally lower in the generic compared to the brand name group (OR: 0.926 [99% CI 0.901–0.951], p<0.001).

Discussion and conclusion: These results suggest that refill compliance is not negatively affected by a physician-induced switch from brand name to generic ramipril products after patent expiry.