Diltiazem in hypertensive patients with type II diabetes mellitus

Twenty-three patients with essential hypertension and diabetes mellitus type II were treated with the calcium antagonist diltiazem (120 to 180 mg twice daily). The mean dose was 307 mg/day. The study was a double-blind, placebo-controlled, crossover design. All measurements were performed 12 to 14 hours after drug intake. Blood pressure, heart rate and forearm blood flow were measured noninvasively. Platelet function was studied by measuring adenosine diphosphate-induced platelet aggregation and the platelet specific proteins, beta thromboglobulin and platelet factor 4. Thromboxane B2 formation in serum and the plasma concentration of diltiazem and its metabolites N-demethyldiltiazem, deacetyldiltiazem and N-demethyldeacetyldiltiazem were measured both during placebo and diltiazem treatment. Diabetic control was evaluated by following HbA1C, fasting blood glucose and urinary glucose. Diltiazem reduced both systolic and diastolic (supine and standing) blood pressure significantly. Forearm blood flow was significantly increased by 32%, p less than 0.05. Supine heart rate decreased significantly, while no such change was seen in the standing position. No significant changes were observed in platelet function during diltiazem treatment. There was no relation between the observed blood pressure reduction and the plasma concentration of diltiazem or its metabolites. A positive correlation between the change in heart rate and the metabolite N-demethyldeacetyldiltiazem was observed (r = 0.647, p = 0.005). Three patients were excluded during diltiazem treatment (skin exanthema, headache and atrial fibrillation) and 1 during placebo treatment (angina pectoris). No negative effect on diabetes control was observed. Thus, diltiazem could be used for treatment of hypertension in diabetic patients.