Drug Receptors N. S.

Drug Action

Drugs of C.N.S
 Elmhurst College
Nervous System Cholinergic Drugs II Adrenergic Drugs II  Chemistry Department
Cholinergic Drugs I Adrenergic Drugs I Adrenergic Drugs III  Virtual ChemBook


Adrenergic Drugs III

Adrenergic Blocking Agents or Antagonists:

Adrenergic blocking agents are drugs that selectively inhibit specific receptor sites from sympathetic stimulation. There are several modes of action which over all result in a depression of adrenergic nerves. Blocking agents may interact with specific alpha and beta receptors. The release of norepinephrine from storage sites may be blocked. The storage of norepinephrine may be inhibited. Drugs in this category are mostly antihypertensive agents. Depression of adrenergic nerves results in a vasodilation effect and relieves high blood pressure caused by a constriction of the capillaries.

Antagonists which block alpha receptors sites include:

Prazosin and analogs - terazosin, doxazosin, trimazosin

These are used to treat hypertension by relaxing arterial and venous smooth muscle, decreasing vascular resistance and venous return, and decreasing blood pressure without a significant increase in heart rate.

Antagonists which block beta receptors sites include:

Hypertension. Inderol or Propranolol and Nadolol is effective in treating mild to moderate hypertension. In severe hypertension, it is useful in preventing the reflex tachycardia that often results from treatment with direct vasodilators.

Xylocholine bromide is an example of an agent which blocks the release of norepinephrine from storage.