1 Phenylephrine-induced contractions of rabbit isolated trigone and urethra were antagonized in a competitive manner by alfuzosin (pA2 7.44 and 7.30, respectively) and prazosin.2 The characteristics of [3H]-prazosin binding to human prostatic adenoma tissue were evaluated.[3H]-prazosin was potently displaced by al-adrenoceptor specific agents including alfuzosin, its (+ )-and (-)-enantiomers and prazosin (IC5o 0.035, 0.023, 0.019 and 0.00411M, respectively), but only weakly by M2-adrenoceptor selective agents, for example, yohimbine (IC50= 6.0 IM). produced dose-related inhibition of the increases in urethral pressure caused by stimulation of sympathetic hypogastric nerves. Prazosin was approximately 5 fold more potent than alfuzosin. When phenylephrine was employed to induce urethral and vascular al-mediated tone simultaneously, prazosin inhibited both stimuli with similar potency whereas alfusozin was 3-5 fold more potent against elevated urethral pressure. This functional uroselectivity of alfuzosin was more evident by the intraduodenal route, since doses of 0.03 and 0.1 mg kg-' alfuzosin inhibited urethral pressure with minimal effects on arterial blood pressure. 5 Alfuzosin is a potent selective a,-adrenoceptor antagonist in tissues of the lower urinary tract including the human prostate. This provides a pharmacological basis for its use in the treatment of benign prostatic hypertrophy.

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A series of para-substituted phenoxypropanolamines has been synthesized and tested for beta-adrenoceptor blocking activity. Some derivatives (8, 11, 12, 20, 21) exhibited greater in vitro potency than the reference drugs metoprolol and propranolol. This series, in contrast to propranolol but similar to metoprolol, possesses cardioselectivity. The 3-[p-[(cycloalkylmethoxy)ethyl]phenoxy]-1-substituted-amino-2-prop anol derivatives 8 (cyclopropylmethoxyethyl: betaxolol) and 11 (cyclobutylmethoxyethyl) produced antihypertensive effects in spontaneously hypertensive rats. Betaxolol (Kerlon, 8) was found to exhibit an appropriate preclinical pharmacological and human pharmacokinetic profile (elevated oral bioavailability and prolonged plasma half-life) for the treatment of chronic cardiovascular diseases such as hypertension and angina.

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A series of N2-[(acylamino)alkyl]-6,7-dimethoxy-2,4-quinazolinediamines was synthesized as potential alpha 1-adrenoceptor antagonists. When administered to spontaneously hypertensive rats at 10 mg/kg po, a number of propanediamine derivatives showed good antihypertensive activity, whereas the ethanediamine derivatives, albeit being structurally more closely related to prazosin, were devoid of this property. The most active derivative, N-[3-[(4-amino-6, 7-dimethoxy-2-quinazolinyl)methylamino]propyl]tetrahydro-2-furancarbo xamide hydrochloride, alfuzosin (12), showed high selectivity for peripheral alpha 1-postjunctional adrenoceptors. At equiactive antihypertensive doses, its effect on the pressor response to postural changes in conscious dog was less marked than that shown by prazosin. In the light of these results, alfuzosin was selected for clinical evaluation.