Prazosin differs from phenoxybenzamine in that prazosin:

• A Produces irreversible alpha-1 blockade
• B Also blocks presynaptic alpha-2 receptors, increasing noradrenaline release
• C Is the drug of choice for management of phaeochromocytoma crisis
• D Is competitive and selective for postsynaptic alpha-1 receptors, sparing alpha-2 receptors ✓

Explanation

Prazosin is a selective competitive alpha-1 blocker that does not antagonize presynaptic alpha-2 receptors; preserving alpha-2 autoreceptor feedback limits reflex tachycardia compared with non-selective blockers. Phenoxybenzamine is a non-selective, irreversible (covalent) alpha blocker used in phaeochromocytoma. Prazosin's selectivity for postsynaptic alpha-1 is its key pharmacological distinction.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.