Effect of alpha-adrenergic blockade on blood pressure, glucose, and lipid metabolism in hypertensive patients with non-insulin-dependent diabetes mellitus. To clarify the long-term effects of alpha-adrenergic blockade on blood pressure, glucose, and lipid metabolism, a selective alpha 1-adrenergic inhibitor (prazosin, 1.0 to 2.0 mg/day in divided doses) was administered as a single antihypertensive agent to 10 (four men and six women, aged 52 to 76 years) hypertensive patients (systolic blood pressure [SBP] greater than or equal to 150 mm Hg or diastolic blood pressure [DBP] greater than or equal to 90 mm Hg) with non-insulin-dependent diabetes mellitus (NIDDM) for up to 20 weeks. Blood pressure, glucose tolerance and immunoreactive insulin (IRI) response to 75 gm oral glucose load, hemoglobin A1 (Hb A1), serum lipid profile, and serum apolipoprotein were examined before and after treatment. SBP and DBP were significantly reduced at 20 weeks after treatment with the selective alpha 1-adrenergic inhibitor (SBP 167 +/- 6 mm Hg versus 152 +/- 7 mm Hg; DBP 81 +/- 3 mm Hg versus 76 +/- 3 mm Hg, (p less than 0.05 and p less than 0.01, respectively). Glucose tolerance and IRI response to glucose load were not significantly changed at 4 and 12 to 20 weeks after selective alpha 1-inhibitor treatment compared with the baseline data before treatment; the level of Hb A1 was not significantly changed at 4 and 20 weeks after treatment. 