Effect of Silodosin on Intraurethral Pressure Increase Induced by Hypogastric Nerve Stimulation in Dogs with Benign Prostatic Hyperplasia

We compared the urethral and cardiovascular eSects of silodosin (selective a1A-adrenoceptor antagonist) ,an ovel medication for benign prostatic hyperplasia (BPH), with those of tamsulosin (selective a1A/a1D-adrenoceptor antagonist) and naftopidil (selective a1D-adrenoceptor antagonist) .W e evaluated the eSects of these three drugs on the increase in intraurethral pressure (IUP) induced by electrical stimulation of the hypogastric nerve in anesthetized dogs with spontaneous BPH. All three drugs dose-dependently reduced both the increase in IUP and the mean blood pressure (MBP). The rank order of potencies was tamsulosin＞silodosin＞naftopidil for the reductions in both IUP and MBP. However, the uroselectivity (ED15 value for hypotensive eSect/ID50 value for reduction in IUP) of silodosin (uroselectivity, 19.8) was about 21 and 4 times higher than that of tamsulosin (0.939) and naftopidil (4.94), respectively. These data suggest that silodosin might be one of the most useful medications for dysuria in BPH patients. Key words―silodosin (KMD-3213); a1A-adrenoceptor; benign prostatic hyperplasia; intraurethral pressure