Naftopidil for the treatment of urinary symptoms in patients with benign prostatic hyperplasia

Naftopidil, approved only in Japan, is an alpha 1-adrenergic receptor antagonist (alpha 1-blocker) used to treat lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH). Different from tamsulosin hydrochloride and silodosin, in that it has higher and extremely higher affinity respectively, for the alpha 1A-adrenergic receptor subtype than for the alpha 1D type, naftopidil has distinct characteristics because it has a three times greater affinity for the alpha 1D-adrenergic receptor subtype than for the alpha 1A subtype. Although well-designed large-scale randomized controlled studies are lacking and the optimal dosage of naftopidil is not always completely determined, previous reports from Japan have shown that naftopidil has superior efficacy to a placebo and comparable efficacy to other alpha 1-blockers such as tamsulosin. On the other hand, the incidences of ejaculatory disorders and intraoperative floppy iris syndrome induced by naftopidil may be lower than for tamsulosin and silodosin having high affinity for the alpha 1A-adrenergic receptor subtype. However, it remains unknown if the efficacy and safety of naftopidil in Japanese is applicable to white, black and Hispanic men having LUTS/BPH in western countries.