Adrenergic antagonist

An Adrenergic antagonist is a pharmaceutical substance that acts to inhibit the action of catecholamines at the adrenergic receptors. It is thus a type of sympatholytic. Many important and commonly prescribed medications are adrenergic antagonists, including prazosin and propanolol. Like all pharmacological receptor antagonists, adrenergic antagonists only show an effect when the receptor's effector is present.

It has the opposite effect as adrenergic agonists.

More specifically, they can be divided into:
 * Alpha blockers
 * Beta blockers

Structure Activity Relationship
If the amine on the Adrenergic agent has a substituent bigger than a tertiary butyl, then the compound becomes an adrenergic antagonist.