Five groups of 12 healthy elderly men were randomized to one of five treatment regimens: (1) 600 mg rifampin (INN, rifampicin) once daily, (2) placebo once daily, (3) 40 mg Upidosin twice a day, (4) 60 mg SB 216469 twice a day, or (5) 40 mg Upidosin three times a day. All medications were taken orally and administered for 7 consecutive days.

Functional studies in isolated rabbit tissues also confirmed the uroselectivity of Upidosin, with substantially higher affinity (Kb = 2-3 nM) being observed in urethra and prostate, compared with ear artery and aorta (Kb = 20-100 nM). In radioligand binding studies with [3H]-prazosin, Upidosin had a high affinity at the alpha 1A-adrenoceptors of the rat cerebral cortex and kidney (9.5-9.8) but a lower affinity at the alpha 1B-adrenoceptors of the rat spleen and liver (7.7-8.2). 3. At cloned rat alpha 1-adrenoceptor subtypes transiently expressed in COS-1 cells and also at cloned human alpha 1-adrenoceptor subtypes stably transfected in Rat-1 cells, Upidosin exhibited a high affinity at the alpha 1a-adrenoceptors (9.6-10.4) with a significantly lower affinity at the alpha 1b-adrenoceptor (8.0-8.4) and an intermediate affinity at the alpha 1d-adrenoceptor (8.7-9.2).