Myocardial Infarction in Newly Diagnosed Hypertensive Medicaid Patients Free of Coronary Heart Disease and Treated with Calcium Channel Blockers

PURPOSE: A retrospective cohort analysis of 1,406 newly diagnosed hypertensive patients, aged 18 to 59, without prior coronary heart disease and initially treated with calcium channel blockers (CCBs) or eight other drug regimens was conducted to evaluate the relative risk of acute myocardial infarction (AMI) among patients on CCBs alone or with a diuretic. MATERIALS AND METHODS: Administrative claims data from Pennsylvaniaʹs Medicaid program were the data source. Patients were followed up from 1987 to 1994. RESULTS: There was a highly significant trend towards prescribing CCBs between 1988 and 1991 (P = 0.0001). A total of 67 AMIs occurred, 33 of which were during original drug therapy. Compared with those treated with beta blockers, the relative risk of AMI among patients treated only with CCBs was 0.49 (95% confidence interval [CI] 0.11 to 2.20). Compared with diuretic therapy, the AMI relative risk associated with CCB therapy was 0.60 (95% CI 0.16 to 2.32) when patient drug regimen was classified based on the first six prescriptions. Several alternative drug regimen classification schemes were tested to evaluate the sensitivity of relative risk of AMI to classification of drug therapy. CONCLUSIONS: The measurement of relative risk of AMI was highly dependent on the study design, including patient selection criteria and classification of patient drug therapy. Previous findings of elevated risk of AMI from CCB antihypertensive therapy could not be confirmed.