Adrenergic drugs antagonist

Vasodilators. Hydralazine causes direct relaxation of arteriolar smooth muscle. An important consequence of this vasodilation, however, is reflex tachycardia (T CO). It may also cause sodium retention (T plasma volume). The resulting increase in CO tends to offset effects of the vasodilator. Therefore, these drugs are most effective when administered along with sympathetic agents such as P-adrenergic receptor antagonists, which prevent unwanted compensatory responses by the heart. 

Rhena-/3-ketoimine derivatives of several selected 2-ethylamino compounds have been prepared (36). These amines include 2-chloroethyl-amine (a DNA-alkylating reagent), cystamine ( a heparin antagonist), histamine (a potent vasodilator), tryptamine and O-methylserotonin (two indole alkaloids), and 0,0-dimethyldopamine (an adrenergic drug derivative). 

Esmolol hydrochloride is a competitive p-adrenergic receptor antagonist it is selective for pT adrenoceptors. In contrast to pindolol, esmolol has little intrinsic sympathomimetic activity, and it differs from propranolol in that it lacks membrane stabilizing activity Of all of the p-adrenergic blocking drugs, this compound has the shortest duration of action because it is an ester, it is hydrolyzed rapidly by plasma esterases and must be used by the intravenous route Esmolol is approved only for the treatment of supraventricular arrhythmias... 

Prazosin Is a selective tti-adrenergic receptor antagonist that, at therapeutic doses, has little activity at a2-adrenergic receptors and clinically insignificant direct vasodilating activity. The drug does not cause the other effects attributed to phentolamine. Most important, it produces less tachycardia than does phentolamine and, therefore, is useful in the treatment of essential hypertension. 

Hoffman BB. Catecholamines, sympathomimetic drugs, and adrenergic receptor antagonists. In Hardman JG, et al, eds. The Pharmacological Basis of Therapeutics. 10th ed. New York McGraw-Hill 2001. 

Hoffman B, Lefkowitz R 1996 Catechoiamines, sympathomimetic drugs and adrenergic receptor antagonists. In Hardman J, Limbird L, Molinoff P et al (eds) Goodman Gilman s the pharmacological basis of therapeutics, 9th edn. McGraw-Hiil, New York, pp. 199-248... 

P-adrenergic receptor antagonists may also provide less benefit than other classes of antihypertensive drugs (45). Nevertheless, P-adrenergic receptor antagonists remain a widely accepted choice for the first-line treatment of hypertension. 

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