Effect of Manidipine as Compared to Atenolol on Platelet Aggregation in Elderly Patients with Isolated Systolic Hypertension and Type II Diabetes Mellitus

Abstract

This study was done to evaluate the effect of treatment with manidipine as compared with atenolol on thrombin-mediated platelet aggregation in elderly patients with isolated systolic hypertension and type II diabetes mellitus. After a 2-week washout placebo period, 60 elderly patients (aged 65-80 years) with isolated systolic hypertension (SBP > 140 mm Hg and DBP < 90 mm Hg) were randomly assigned to manidipine 10 mg or atenolol 50 mg 6-week treatment according to a double-blind, crossover design. Thirty patients had a concomitant well-controlled type 2 diabetes mellitus (HbA1c < or = 6.5%). At the end of the washout and of each treatment period, blood pressure (BP) (by mercury sphygmomanometer) and platelet aggregation (by Born-type aggregometer) were evaluated. Blood samples were collected using sodium citrate as anticoagulant, and platelet aggregation was induced by 2 different concentrations of ADP and collagen. Manidipine and atenolol produced a significant BP reduction in both diabetic and nondiabetic patients, with no difference between treatments. Despite the similar BP effect, in diabetic patients manidipine produced a significant reduction in platelet aggregation induced by both doses of either ADP or collagen. In nondiabetic hypertensives, manidipine inhibited platelet aggregation only at the highest doses of both inducers. The difference in the platelet inhibitory effect of manidipine between diabetic and nondiabetic subjects was statistically significant (P < 0.05) at both inducer concentrations. No changes in platelet aggregation were observed in the atenolol group. These data indicate that, unlike atenolol, manidipine inhibits platelet aggregation in elderly hypertensive patients, expecially in those with associated type II diabetes mellitus. The clinical impact of this positive effect in terms of prevention of cardiovascular complications in these high-risk patients remains to be clarified.