- Phenoxybenzamine is a haloalkylamine. Used as a vasodilator in hypertensive emergencies like in pheochromacytoma; also used in the management of CRPS. Used in the management of intraarterial injection of thiopentone too.
- It is a non-selective alpha blocker. It binds covalently to the receptors. So it behaves like a competitive irreversible antagonist.New receptors must be synthesised to overcome drug effect. Blockade of alpha 2 receptors increases the amount of noradrenaline released: produces tachycardia. Partial agonist at 5-HT2 receptors
- Available as capsules of 10 mg and solution: 50 mg/mL for iv use. Oral dose is 10–60 mg per day in divided doses and IV: 10–40 mg over 1 hour. Effects may lasts for 3–4 days
- CVS: Vasodilation and fall in BP, but tachycardia increase CO
- CNS: Sedation. Rapid infusion can cause seizures
The Lay Medical Man 