Patterns of amlodipine and felodipine use in an elderly Quebec population

To assess drug prescription patterns and medical resource consumption in an elderly population in Quebec receiving amlodipine or felodipine for the treatment of hypertension.

Sociodemographic, clinical and drug claim data for a random sample of hypertensive patients 65 years of age and older with at least one claim for amlodipine or felodipine between August 1, 1990 and August 31, 1997 were extracted from the Régie de l'assurance maladie du Québec (RAMQ) database. Patterns of prescription renewal, drug switch and compliance rates, and health care resource use were established for both an amlodipine and a felodipine group. Long term persistence on treatment was quantified by survival curve analysis.

The amlodipine (5188 patients) and felodipine (2630 patients) groups were similar in terms of sex ratio (66.7% female) and age (mean 74 years). Average compliance rates for amlodipine patients (67.9%) were significantly higher than for felodipine patients (66.2%) (P<0.01), and switch rates were 5.4-fold higher in the latter group. Patients initiating treatment with felodipine had a 27% increased rate of discontinuation (relative risk 1.27) compared with the amlodipine patients. In addition, patients with at least one year of follow-up data were more likely to maintain amlodipine as part of their antihypertensive regimens than felodipine. After adjustment, medical resource consumption patterns were similar for both groups except for an increase in the number of specialist visits for the amlodipine treatment group.

Patients who received amlodipine, either as a monotherapy or as part of a multitherapy regimen, were more compliant and persistent with their treatment than patients on felodipine. The data suggest that amlodipine may provide more effective long term hypertension control than felodipine, and that the two drugs are not therapeutically equivalent.