Tamsulosin, a selective alpha1 adrenoceptor blocking agent, exhibits its selectivity for alpha1?A adrenoceptors in human prostate. Blockade of these adrenoceptors can cause smooth muscle in the bladder neck and prostate to relax, resulting in an improvement in urine flow rate and a reduction in symptoms of BPH. Absorption of Tamsulosin hydrochloride capsule 0.4mg is essentially complete (90%) following oral administration under fasting conditions. The time to maximum concentration (Tmax) is reached by four to five hours under fasting conditions and by six to seven hours when administered with food. Tamsulosin hydrochloride is extremely bound to human plasma protein (94% to 99%). Tamsulosin hydrochloride is extensively metabolized by cytochrome P 450 enzymes in the liver and less than 10% of the dose is excreted in urine as unchanged form. Following intravenous or oral administration of an immediate-release formulation the elimination half-life of Tamsulosin hydrochloride in plasma ranges from five to seven hours. Because of the absorption rate controlled pharmacokinetics with Prostam capsules, the apparent half-life of Tamsulosin hydrochloride is approximately 9 to 13 hours in healthy volunteers and 14 to 15 hours in the target population.