THE EFFECTS OF NITRENDIPINE ON GLUCOSE-TOLERANCE AND IMMUNOREACTIVE INSULIN LEVELS IN HYPERTENSIVE PATIENTS

This study evaluated glucose metabolism and insulin release in 30 hype rtensive patients before and after a 4-week treatment period with nitr endipine, 20 mg once daily. Results of an oral glucose tolerance test (OGTT) showed an increase in plasma glucose and no significant change in immunoreactive insulin levels, after nitrendipine treatment, in hyp ertensive normoglycemic patients (group 1). Plasma glucose levels were significantly unchanged and immunoreactive insulin levels were signif icantly reduced in hypertensive patients with impaired glucose toleran ce (group 2). A significant decrease in plasma glucose was observed at the second half of the OGTT, and a significant increase in immunoreac tive insulin levels was measured before and 30 minutes after a glucose load in hypertensive diabetic patients (group 3). No significant chan ge of serum fructosamine levels was evident in any group. In conclusio n, the effects of nitrendipine on glucose metabolism, which differ whe n the study groups are considered individually, do not appear to be cl inically relevant and may have only a speculative value. Some explanat ory hypotheses are suggested: (1) release of inactive insulin; (2) a d irect effect of nitrendipine on the pancreatic beta-cell; (3) interfer ence with the release of humoral and/ or hormonal factors; (4) nondecr eased hepatic glucose output; and (5) effect of nitrendipine on insuli n receptor and/or postreceptor events.