ADRENERGIC ANTAGONISTS

Adrenergic antagonists prevent the response of adrenergic nerve stimulation. These drugs block either alpha (α) or beta (β) adrenergic receptors. Adrenergic blocking agents of the a-type are ergot alkaloids (e.g. ergonovine, ergotamine, ydroergotamine), yohimbine alkaloids (e.g. yohimbine), and benzodioxanes. The adrenergic blockers apparently possess suitable affinity for adrenergic o-receptors but lack of the intrinsic activity characteristic of the natural neuroeffector.


β-Adrenergic blocking drugs are structurally related to isopropylarterenol. They block the actions of catecholamines mediated through β-receptor stimulation. Thus, the f-receptor stimulating action of adrenaline and isoproterenol are blocked but positive chronotropic effects of calcium, barium, theophylline and digitalis are not affected. Sotalol, timolol, dichloroisoproterenol (DCI), oxprenolol, pindolol, propranol, acebutolol, atenolol, metoprolol and labetalol are the β -adrenergic blocking agents.

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