Real-world adherence to dihydropyridine calcium-channel blockers: a pharmacoepidemiologic study

Introduction: Low medication adherence contributes to uncontrolled cardiovascular (CV) risk. Aims: This study investigated 12- and 24-month adherence, all-cause mortality and CV events in subjects receiving originator or generic dihydropyridine calcium-channel blockers (CCBs) as recorded in administrative databases from Local Health Units across several Italian regions. Methods: We retrospectively analysed databases containing demographics and vital status, drug prescriptions, and hospital discharge diagnoses for more than 6 million individuals. Subjects receiving lercanidipine originator, generic lercanidipine, amlodipine originator, or generic amlodipine were included. Subjects with prior or occasional CCB use, inadequate follow-up time, chronic ischaemic heart disease or acute pulmonary heart disease, or switching between CCBs were excluded. Adherence was defined as a Proportion of Days Covered ≥ 80% at 12 and 24 months. Cox regression models estimated the association between treatments and a composite of all-cause mortality and CV events. Results: Adherence was assessed in 3,860 propensity-score-matched subjects (965/group), selected from 14,849 eligible subjects. Lercanidipine originator was associated with higher (p < 0.001) 12-month (43%) and 24-month (38%) adherence than generic lercanidipine (31 and 26%) and amlodipine originator (22 and 19%). The events analysis included 15,808 subjects. Compared with originator lercanidipine, originator amlodipine, generic lercanidipine and generic amlodipine were associated with 43%, 30% and 33% higher hazards of the composite outcome, respectively (corresponding 95% Confidence Intervals: 1.28–1.60, 1.10–1.55, 1.17–1.50). Conclusions: Medium-term adherence was low across all treatments. Originator lercanidipine was associated with the highest adherence, with lower adjusted hazards of the composite outcome and all-cause mortality compared to the other treatments.