Effect of bunazosin and atenolol on glucose metabolism in obese, nondiabetic patients with primary hypertension.

Antihypertensive drugs, recommended by the World Health Organization for use in monotherapy, exert different effects on glucose and lipid metabolism. In our study we compared the effects of the beta-blocker atenolol (AT) and the alpha1-blocker bunazosin (BU) on glucose metabolism. The doses administered were chosen to produce similar antihypertensive effects with both drugs. The study was conducted as a bicenter, parallel, controlled, and double-blind study. All patients suffered from mild to moderate primary hypertension, were obese (body mass index > 26 kg/m2), but were nondiabetic. After a drug-free period of 4 weeks, patients were treated either with 6 and 12 mg of bunazosin (n = 15) or with 50 and 100 mg of atenolol (n = 17) once daily for 12 weeks. Glucose metabolism was measured by the iv glucose tolerance test (GTT) and the euglycemic hyperinsulinemic clamp test. The results show a similar blood pressure reduction with both drugs. However, their effects on glucose metabolism were significantly (p < 0.05) different: The area under the curve (AUC) of glucose in the iv GTT increased 26.8% during atenolol treatment but decreased 30% during bunazosin treatment. The same influence on the AUC of insulin was observed [AT +478.5 +/- 441.8 (+22%) vs. BU, -588.5 +/- 411.1 (-22%)]. Similar changes were found in the glucose clamp test. The metabolic clearance rate increased 11.4% during bunazosin use and decreased 8.4% during atenolol use to the same degree that the insulin sensitivity index changed (BU +13.2% vs. AT -21.9%). The differences between the two treatment regimes were statistically significant (p < 0.05). These results in obese hypertensives confirm the well-known negative effects of beta-blockers on glucose metabolism. Additionally, they demonstrate that an alpha1-blocker such as bunazosin develops the same blood pressure-lowering effect as beta-blockers, but with a significantly better profile with regard to glucose metabolism. Therefore, the use of alpha1-blockers can be recommended for obese hypertensives without any special care for glucose metabolism.