A single (investigator)-blind randomised control trial comparing the effects of quinapril and nifedipine on platelet function in patients with mild to moderate hypertension

The effect of quinapril and nifedipine on platelet aggregation, vascular en dothelial function and coagulation system activity, was compared in a paral lel-group, investigator-blind study carried out on patients with mild to mo derate hypertension but no other diseases or receiving medication which mig ht affect platelet function, vascular endothelium or coagulation. Forty pat ients (two groups of 20 patients each) and 20 control subjects were recruit ed. Patients were randomised to receive either quinapril or nifedipine reta rd and the dose escalated to control hypertension. Platelet aggregation stu dies were assessed serially and beta -thromboglobulin, angiotensin-converti ng enzyme (ACE), von Willebrand factor (vWF) coagulation factors VIIIc, XII and fibrinogen were measured at the beginning and end of the 12-week perio d. Blood pressure was adequately controlled in all patients in both groups. Platelet function was impaired in certain parameters (slope of the reactio n with ADP and collagen and maximum aggregation with collagen) in the patie nt group compared to controls before treatment and this improved in patient s on quinapril but not on nifedipine; likewise beta -thromboglobulin was hi gher in the patient group and fell significantly in the quinapril group but not those on nifedipine. Measurements of endothelial function and coagulat ion were normal before treatment and showed no alteration during the study, except in the expected fall in plasma ACE in the quinapril group. The resu lts indicate that the ACE inhibitor, quinapril, has a beneficial effect on platelet function unlike the calcium channel blocker, nifedipine.