<qa>  What is the highest selectivity ratio for the prostate over the vascular tissue?Alfuzosin hydrochloride was approved by the FDA for treatment of the signs and symptoms of BPH in 2003. Alfuzosin differs from other 1-adrenergic receptor blockers by the absences of a piperidine moiety and the presence of a diaminopropyl spacer, which confers alfuzosin with specific biochemical properties. Affinity studies on human-cloned 1 receptor subtypes show that alfuzosin, like terazosin and doxazosin, is devoid of significant receptor subtype selectivity. In isolated human tissues, however, alfuzosin displays the highest selectivity ratio for the prostate over the vascular tissue ratio, 544 compared with tamsulosin 90, doxazosin 51, and terazosin 19. 