Tamsulosin contains the active substance tamsulosin hydrochloride, which belongs to a groupof medicines called alpha adrenoceptor blockers.Tamsulosin relaxes:- the muscles in the prostate gland, and- the tube from the bladder to the outside (the urethra).This lets urine pass more easily through the urethra, making it easier to urinate.Tamsulosin is for men who have benign prostate enlargement (benign prostatic hyperplasia,BPH). This is when the prostate gland increases in size. This can make it difficult to passurine. This means you may have to pass urine often or during the night. You may also feel thatyou still need to pass urine even after having done so. You may also dribble after passingurine.