Tamsulosin is a selective alpha-1 adrenoceptor blocker. It blocks alpha-1 adrenoceptors, which are abundant in the prostate, prostatic capsule, prostatic urethra, and bladder neck, resulting relaxation of these adrenoceptors in the bladder neck and prostate. Thus, there is an improvement in urine flow rate and reduction in symptoms of benign prostatic hypertrophy (BPH). Dutasteride inhibits 5 alpha-reductase, the enzyme responsible for conversion of testosterone to 5 alpha-dihydrotestosterone (DHT). DHT appears to be the principal androgen responsible for stimulation of prostatic growth.