Select the drug which can improve urinary flow rate in benign prostatic hyperophy without affecting prostate size

a ADRENERGIC BLOCKING DRUGS a1 selective--Prazosin, Terazosin,etc.. Prazosin:- It is first of the highly selective a1 blockers having a1 : a2 selectivity ratio 1000:1. All subtypes of a1 receptor (a1A, a1B, a1D) are blocked equally. It blocks sympathetically mediated vasoconstriction and produces fall in BP which is attended by only mild tachycardia; Prazosin dilates aerioles more than veins. Postural hypotension is less marked, occurs especially in the beginning, which may cause dizziness and fainting as 'first dose effect'. This can be minimized by staing with a low dose and taking it at bedtime. Subsequently tolerance develops to this side effect. uses:- Prazosin is primarily used as an antihypertensive. Other uses are--Raynaud's disease and benign hyperophy of prostate (BHP). Prazosin blocks a1 receptors in bladder trigone and prostatic smooth muscle, thereby improves urine flow, reduces residual urine in bladder. Ref:- kd tripathi; pg num:-140,142