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CD23 [Mar96] [Jul96] [Jul00] [Apr01] Phentolamine:

A. Is a selective alpha-1 antagonist
B. Binds covalently to the alpha receptor
C. Causes bradycardia
D. Is a selective alpha-2 antagonist
E. Increases cardiac output

User Aniqa
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1 Answer

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Final answer:

Phentolamine is a non-selective alpha-blocker that antagonizes both alpha-1 and alpha-2 adrenergic receptors, it does not bind covalently to the receptors, and typically causes tachycardia, not bradycardia, leading to increased cardiac output.

Step-by-step explanation:

The question pertains to Phentolamine, which is a sympatholytic drug. Phentolamine is not a selective alpha-1 antagonist; rather, it is a non-selective alpha-blocker, meaning it antagonizes both α1 and α2 adrenergic receptors, preventing the normal sympathetic effects that epinephrine and norepinephrine would have, such as vasoconstriction. Therefore, it often leads to vasodilation and a drop in blood pressure.

It does not bind covalently to the alpha receptor; it is a reversible antagonist. Because of the blockage of α-adrenergic receptors, there can be a reflex increase in heart rate (tachycardia), rather than bradycardia, in response to vasodilation and lowered blood pressure. Phentolamine can lead to increased cardiac output due to decreased peripheral resistance.

User Sebastian Krogull
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