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