LESSONS FROM COMBINATION THERAPY IN VETERANS AFFAIRS STUDIES

A subset of 102 patients of an original cohort of 1292 with stage 1 to 2 hypertension was characterized by having failed to achieve goal blo od pressure (< 90 mm Hg diastolic) after treatment with two single ant ihypertensive drugs. These patients were given a combination of the tw o drugs on which they had failed to achieve blood pressure goal when t hey were administered as single-drug therapy. The drugs were hydrochlo rothiazide, atenolol, captopril, diltiazem-SR, clonidine, and prazosin . We examined the responses in each of the drug combination categories by the order that the drugs were administered, by estimated total res ponse rates for the combinations, and by age and race. The order of dr ug administration did have an effect for some of the drug pairs. This was of two types: 1) different results for each member of the pair, bu t the same combination result; and 2) different end result of the comb ination. An example of the first type is that prazosin had only a 6% r esponse rate in patients who had failed on diltiazem, while diltiazem had a 22% response rate in patients who had failed on prazosin. Nevert heless, the combinations yielded the same total responses (86% and 84% ) regardless of order. An example of the second type is that captopril -diltiazem was less effective in total response than diltiazem-captopr il (88% v 97%). Differences were seen in the response to combinations in the race and age groups. There were ordering differences of type si milar to those described above. We conclude that combination drug ther apy is highly effective even when the individual components have faile d and that some differences in response by order of drug administratio n may occur. (C) 1996 American Journal of Hypertension, Ltd.