Naftopidil (INN, marketed under the brand name Flivas) is a drug used in benign prostatic hypertrophy which acts as a selective α1-adrenergic receptor antagonist or alpha blocker. Naftopidil (INN, marketed under the brand name Flivas) is a drug used in benign prostatic hypertrophy which acts as a selective α1-adrenergic receptor antagonist or alpha blocker.