Glycaemic control and exercise tolerance in hypertensive insulin‐treated diabetes during nifedipine therapy

Abstract

Controversy continues over the effects of calcium antagonists on glucose homeostasis and cardiac function, particularly in diabetics. Changes in blood pressure, exercise tolerance, insulin secretion and glycaemic control were studied therefore in 12 insulin-treated hypertensive diabetics with varying endogenous insulin reserve who were given nifedipine 20 mg twice daily for six weeks. Six hypertensive diabetic subjects off all antihypertensive medication served as controls.Glycaemic control and blood pressure did not alter in the control group over the six week period. In the nifedipine-treated group blood pressure levels remained significantly improved at six weeks with systolic pressure falling from 178 ±24 to 158 ±20 (p<O.Ol) and diastolic pressure from 101 ± 13 to 80 ± 13 mmHg (p<O.Ol).Initial mean blood glucose levels (10.2 ± 3.4 mmol/l) did not alter at three weeks (11.5 ± 3.1 mmol/l) or at six weeks (9.9 ± 2.5 mmol/l), and HbA, was likewise unchanged, 9.5 ± 1.4 before and 9.2 ± 1.1% after treatment, as were fasting blood glucose and M values. No difference in glycaemic control with nifedipine was seen between the six patients with and the six without detectable C peptide levels. Furthermore, no change in C peptide secretion was found after six weeks treatment in the patients with residual endogenous insulin secretion.Exercise tolerance in 10 of the patients assessed by changes during treadmill testing in heart rate, blood pressure and duration of exercise, was not impaired by nifedipine. In fact, in the six with coexistent ischaemic heart disease, a significant improvement in ST depression from 3.1 to 1.5 mm (p < 0.05) was observed.We conclude that nifedipine lowers blood pressure effectively in insulin-treated hyperten-