Tamsulosin is a treatment for difficult urination, a common symptom of enlarged prostate. Tamsulosin, and other medications in the class called alpha blockers, work by relaxing bladder neck muscles and muscle fibers in the prostate itself and make it easier to urinate. More specifically, tamsulosin is an 1a-selective alpha blocker used in the symptomatic treatment of benign prostatic hyperplasia (BPH). Tamsulosin was developed by Yamanouchi Pharmaceuticals (now part of Astellas Pharma) and was first marketed in 1996 under the trade name Flomax. The U.S. patent for Flomax expired in October 2009. The U.S. Food and Drug Administration (FDA) approved generic Flomax in March 2010.