SN instructed patient / caregiver that Tamsulosin is used in the treatment of difficult urination, a common symptom of enlarged prostate ( BPH ). Tamsulosin works by relaxing bladder neck muscles and muscle fibers in the prostate itself and make it easier to urinate. Possible side effect may include, Higher risk of allergic reaction in those with sulfa allergies. Patients taking tamsulosin are prone to a complication known as floppy iris syndrome during cataract surgery. Severe hypotension. It also affect sexual function in men. It can cause males to experience retrograde ejaculation.