Tamsulosin, sold under the brand name Flomax among others, is a medication used to treat symptomatic benign prostatic hyperplasia (BPH) and chronic prostatitis and to help with the passage of kidney stones. The evidence for benefit with a kidney stone is better when the stone is larger. It is taken by mouth. Common side effects include dizziness, headache, sleeplessness, nausea, blurry vision, and sexual problems. Other side effects may include feeling lightheaded with standing and angioedema. Tamsulosin is an alpha blocker and works by relaxing muscles in the prostate. Specifically it is an α1 adrenergic receptor blocker. Tamsulosin was approved for medical use in the United States in 1997. It is available as a generic medication. In 2020, it was the 24th-most commonly prescribed medication in the United States, with more than 24million prescriptions. Medical uses Tamsulosin is primarily used for benign prostatic hyperplasia (BPH) and to help with the passage of kidney stones. Tamsulosin, however, appears to be effective only for stones over 4 mm and less than 10 mm in size. Tamsulosin is also used as an add-on treatment for acute urinary retention. People may void more successfully after catheter removal if they are taking tamsulosin. People taking tamsulosin also are less likely to need recatheterization. Tamsulosin does not decrease the overall size of the prostate in men with BPH, and is not recommended for prevention of prostate cancer. Combination therapy The results of the CombAT (combination of dutasteride (Avodart) and tamsulosin, under the brand name Duodart) trial in 2008 demonstrated that treatment with the combination of dutasteride and tamsulosin provides greater symptom benefits compared to monotherapy with either agent alone for treatment of benign prostatic hyperplasia. The CombAT trial became the medication Jalyn. It was approved by the FDA on 14 June 2010. This combination can be useful because it may take up to six months for symptomatic relief to be found when using 5-alpha-reductase inhibitors such as dutasteride compared to alpha-1 receptor blockers, which can provide relief in some cases within 48 hours. Adverse effects Eyes: People taking tamsulosin are prone to a complication known as floppy iris syndrome during cataract surgery. Adverse outcomes of the surgery are greatly reduced by the surgeon's prior knowledge of the person's history with this drug, and thus having the option of alternative techniques. Severe hypotension. Persons with cardiac conditions including hypotension, mechanical heart failure (valvular, pulmonary embolism, pericarditis), and