What is Rapaflo? Rapaflo (silodosin) is an alpha-adrenergic (AL-fa ad-ren-ER-jik) blocker. Rapaflo helps relax the muscles in the prostate and bladder neck, making it easier to urinate. Rapaflo is used to improve urination in men with benign prostatic hyperplasia (enlarged prostate). You should not take Rapaflo if you have severe kidney or liver disease. Do not take silodosin together with similar medicines such as alfuzosin, doxazosin, prazosin, tamsulosin, or terazosin.