Effects of doxazosin, a selective alpha 1-inhibitor, on plasma insulin and blood glucose response to a glucose tolerance test in essential hypertension.

Essential hypertension is characterized by an insulin-resistance state that may be responsible for the increased atherogenesis typical of this disease. To investigate the effect on glucose and insulin metabolism of doxazosin, an antihypertensive drug whose favorable impact on lipid metabolism is well known, 10 newly diagnosed essential hypertensive patients of the same age and body mass index (BMI) were selected for our study. They underwent an oral glucose tolerance test (OGTT) with measurement of plasma insulin levels before and after a 6-month treatment period with doxazosin. In this period of time, they took no other drugs and followed no diets, nor did their weights vary. The daily dose of doxazosin was increased (maximum, 8 mg) to achieve a normotensive blood pressure (< 140/90). At the end of treatment, total and low-density lipoprotein (LDL) cholesterol levels (225 +/- 18 v 200 +/- 16 and 177 +/- 8 v 150 +/- 7 mg/dL, respectively; P < .05) were decreased, confirming the lipid-lowering effect of the drug. The OGTT showed a significant decrease of plasma insulin (16.04 +/- 1.8 v 10.99 +/- 0.9 mU/mL.min, P < .05) and blood glucose (22.54 +/- 1.6 v 20.83 +/- 1.6 g/dL.min, P < .05) areas. The glucose to insulin ratio, also known as the insulin sensitivity index, increased (1.56 +/- 0.15 v 1.95 +/- 0.12, P < .05). These findings seem to provide evidence of a favorable effect of doxazosin on insulin action.