Frequency of cardiovascular events in patients treated with anti hypertensive agents: A cohort study based on claims data generated by primary care practice.

Background: Large-scale clinical trials have shown that antihypertensive drugs reduce the risk for cardiovascular events. However, little is known about the effectiveness of these drugs in the primary care setting.

Objective: The aim of this study was to investigate the frequency of cardiovascularevents during treatment with either of 2 of the most frequently prescribed antihypertensive drugs.

Methods: This observational, longitudinal, cohort study considered the entirepopulation listed in the administrative databases of the Local Health Authority of Ravenna, Italy (356,000 residents). The demographic registry and the pharmaceutical and nosocomial databases were cross-linked to determine drug treatment, as well as the frequency of cardiovascular events on a patient-by-patient basis. Each patient aged >18 years receiving a first prescription for amlodipine or enalapril in the period between January 1, 1996, and December 31, 2000, with ≥6 months of continuous treatment with the drug was included. The follow-up period varied from 6 months to 4.5 years.

Results: Of the 7500 patients analyzed (4092 women and 3408 men; mean[SD] age, 68.0 [12.4] years), 2231 (29.7%) were given amlodipine and 5269 (70.3%) were given enalapril. The observed rate of cardiovascular events was higher among patients treated with amlodipine (54 per 1000 patient-years vs 46 per 1000 patient-years; P = 0.007), with a hazard ratio 17% higher compared with enalapril (95% Cl, 5.0-24.0; P = 0.007). The result was also confirmed using Cox multivariate regression analysis. The combination of enalapril plus diuretic showed the lowest risk for cardiovascular events (0.73; 95% Cl, -36.0 to -16.0; P < 0.001).

Conclusion: This analysis showed that treatment with enalapril was associatedwith a significantly lower frequency of cardiovascular events compared with amlodipine.