Hypertension is common in patients with type 2 diabetes mellitus (DM), and contributes to the progression of its complications in patients with diabetes. Doxazosin is a selective alpha 1-adrenoceptor-blocking anti-hypertensive agent and has a favorable impact upon lipid metabolism. We investigated the effect of doxazosin on the lipid metabolism in hypertensive patients with type 2 diabetes, especially low-density lipoprotein (LDL) particle size that is associated with many elements of the insulin resistance syndrome. Cross-sectional study (n = 19) was designed to determine whether doxazosin, administered with an angiotensin II converting enzyme inhibitor (ACEI) and a Ca antagonist, affects LDL particle size. As a follow-up study (n = 6), lipid and glucose metabolism and LDL particle size were followed for 12 weeks before and after the initiation of doxazosin administration (1-4 mg/day). The average size of LDL particle was significantly larger in the patients treated with doxazosin (LDL-migration index (LDL-MI): 0.348 +/- 0.027) than those in the patient treated without doxazosin (0.378 +/- 0.035), although LDL cholesterol levels did not differ between the two groups. The plasma glucose and HbAlc levels remained unchanged. Lipid profile showed normolipemia throughout the period of the study. However, LDL particle size was demonstrated to become larger during the following period. Small LDL fraction (LDL3-7) diminished remarkably and large LDL (LDL1-2) increased on the polyacrylamide gel electrophoresis (PAGE) LDL system (LipoPrint). From this pilot study, it was concluded that doxazosin is a useful anti-hypertensive agent for hypertensive type 2 diabetic patients in improving the size of LDL particle. (C) 2000 Elsevier Science Inc. All rights reserved.