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.