Vasodilation-related adverse events in diltiazem and dihydropyridine calcium antagonists studied by prescription-event monitoring.

The incidence of vasodilation-related events (flushing, headache, dizziness and oedema) was determined in a total of 37,670 patients treated with diltiazem, nicardipine, isradipine or amlodipine and studied by Prescription-Event Monitoring between 1984 and 1991. Event rates are expressed as the percentage of patients who experienced these events during the six months after the first prescription. The rates for all these events with the newer vasoselective dihydropyridines (nicardipine, isradipine and amlodipine) were higher than those with diltiazem. Among the three dihydropyridines, there were large individual differences in the rates. With nicardipine, the frequency of each of the four vasodilation-related events were similar to one another (approximately 3%). With isradipine, the rates were also similar to one another but all were approximately twice those measured in the nicardipine study (approximately 6%). These differences may have been due to confounding factors such as the publicity about adverse drug reactions, the indication for use by individual patients or the doses actually being used at the time the event occurred. With amlodipine, in contrast, the rate for oedema was two to four times larger than the rates for flushing, headache or dizziness.