Tamsulosin is used in men to treat the symptoms of an enlarged prostate (benign prostatic hyperplasia or BPH) which include difficulty urinating (hesitation, dribbling, weak stream, and incomplete bladder emptying), painful urination, and urinary frequency and urgency. Tamsulosin is in a class of medications called alpha blockers. It works by relaxing the muscles in the prostate and bladder so that urine can flow easily.
Tamsulosin comes as a capsule to take by mouth. It is usually taken once a day. Take tamsulosin 30 minutes after the same meal each day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take tamsulosin exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Summary from MedlinePlus.gov, click for more information.