Adrenergic Blocking Agents...Pharmacology

• Adrenergic blocking agents are drugs that selectively inhibit specific receptor sites from sympathetic stimulation.
• Blocking agents may interact with specific alpha and beta receptors. The release of nor-epinephrine from storage sites may be blocked.

Types of Adrenergic Blocking Agents

Adrenergic blocking agents are of two types;

• α-Blockers
• β-Blockers

α-Blockers

• Phenoxybenzamine is the prototype drug which blocks α-1 and α-2 receptors.
• Phentolamine, Tolezoline…… blocks α-1 and α-2 receptors
• Przosine, Doxazosine, Terazosine….. Blocks α-1 receptors
• Atipamazole…. blocks α-2 receptors

β-Blockers

• Propranalol is the prototype drug which blocks both types of beta receptors.
• Timolol, Ndolol, Pindolol also block the both types of beta receptors.
• Atinilol, Esmalol blocks beta-1 receptors.
• Butamoxine blocks beta-2 receptors.
• Labetalol, Carvedalol block both alpha & beta receptors.

Therapeutic Uses

α-Blockers

• Phenoxybenzamine blocks α-1 and α-2 receptors by making covalent bond, It is irreversible inhibition.
• Other alpha blockers are reversible inhibitors.
• For hypertension, these drugs are used.
• Orthostatic Hypotension…In standing condition, hypotension occurs due to these drugs. So, initial dose should be given before bed.
• Pheochromocytoma….Tumor of chromafin cells in adrenal glands, so, adrenaline quantity increased and Blood pressure remains constantly high. To diagnose it, phenoxybenze is used which will lower the blood pressure.
• To remove the toxicity of α-2 agonists, alpha-2 antagonists are used.

β-Blockers

• These are used as anti-hypertensive drugs. E.g. propranalol
• Timolol is used to treat glaucoma by decreasing the intraocular pressure.