The INSIGHT and NORDIL Trials: Are Calcium Antagonists Equivalent to Established Drug Therapies for Cardiovascular Protection?

Calcium channel blockers have come into worldwide use for treating hypertension and other circulatory disorders. In recent years, results of several observational studies have suggested that these drugs may not be as safe or effective as other available therapies, such as diuretics and beta-blockers, in the prevention of cardiovascular events. The Nordic Diltiazem (NORDIL) and the International Nifedipine GITS Study: Intervention as a Goal in Hypertension Treatment (INSIGHT) studies were the first two randomized interventional trials in hypertensive patients that directly compared the effects of therapy based on calcium antagonists with those of diuretic and beta-blocker-based treatment on major cardiovascular endpoints. Both studies found that the effectiveness of calcium antagonist therapy was similar to that of diuretic and beta-blocker therapy for preventing the composite primary endpoint of fatal and nonfatal stroke, myocardial infarction, and other cardiovascular death. The two studies shared several nonsignificant trends for cause-specific events, including greater stroke prevention and lesser coronary event prevention in the calcium antagonist groups compared with the diuretic and beta-blocker groups. There is not yet sufficient evidence to prove whether cause-specific differences exist. Results of the NORDIL and INSIGHT studies support incorporating calcium antagonist-based therapy as an additional safe and effective approach for preventing blood pressure-related illness and death.