A comparison of the effects of tamsulosin and alfuzosin on neurally evoked increases in bladder neck and seminal vesicle pressure in rats

To assess the effects of the alpha1-adrenoceptor antagonists alfuzosin and tamsulosin on the physiological events associated with ejaculation in the rat, because when these drugs are used for treating symptomatic benign prostatic hyperplasia in men they may affect ejaculation by impairing bladder neck closure and seminal vesicle contraction. In clinical trials the incidence of ejaculatory disorders in men is typically < 1% with alfuzosin and 4-18% with tamsulosin. The effects of tamsulosin and alfuzosin on bladder neck and seminal vesicle pressures (BNP and SVP) in the rat were analysed. Increases in BNP and SVP were induced in urethane-anaesthetized Wistar rats by electrical stimulation (ES) of the hypogastric nerve (HN) before and after an intravenous injection with vehicle, 3 or 10 mug/kg of tamsulosin or alfuzosin (10 rats/group). The mean amplitude and area under the curve (AUC) of the BNP and SVP were expressed as the percentage of the response to ES of HN before the treatment. The amplitude and AUC of the SVP were significantly decreased by both doses of tamsulosin, and marginally decreased by the same doses of alfuzosin. The amplitude of the BNP was significantly decreased by 3 and 10 mug/kg of tamsulosin and 10 mug/kg alfuzosin, and marginally decreased by 3 mug/kg alfuzosin. The AUC of the BNP was significantly decreased by both doses of tamsulosin, but barely affected by alfuzosin at the same doses. Over the doses assessed, alfuzosin had significantly less deleterious effect on increases in BNP and SVP induced by ES of the HN than had tamsulosin.