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MCQ on antihypertensives: Page-7

All of the following are potassium channel activators EXCEPT

(A) Minoxidil

(B) Chromokalim

(C) Sotalol

(D) Nicorandil

Sotalol is a voltage gated potassium channel blocker that present on the heart and indicated as antiarrhythmic agent. Minoxidil, chromokalim and nicorandil are Ach-sensitive potassium channel blockers which are present on vascular smooth muscle.

Which of the following category of drug are selective for vascular smooth muscle

(A) Dihydropyridines

(B) Phenylalkylamines

(C) Dibenzoazepines

(D) All of the above

Calcium channel blockers chemically belong to three classes. Verapamil is a phenylalkylamine, diltiazem is a benzothiazepine and nifedipine, nimodipine are dihydropyridines. Among these verapamil is selective for cardiac muscle whereas dihydropyridines are selective for smooth muscle. Diltiazem acts on both cardiac as well as smooth muscle.

Which of the following drug has increased risk of reflex tachycardia

(A) Verapamil

(B) Diltiazem

(C) Nifedipine

(D) Captopril

Dihydropyridines like nifedipine are selective for smooth muscle and produce direct vasodilatation. Because of this vasodilatation, perfusion pressure decreases and baroreceptor reflex is stimulated leading to increased central sympathetic discharge. This results in release of noradrenaline and adrenaline which act on heart to produce tachycardia. Verapamil directly acts on cardiac muscle hence produces bradycardia.

One of the important toxic effect of nitroprusside is

(A) Hypertension

(B) Neutropenia

(C) Decreased thyroid function

(D) angio-odema

Sodium nitroprusside is given by IV route and it can be converted into thiocyanate in the body which on accumulation may inhibit thyroid function.

The toxicity of sodium nitroprusside is due to

(A) Accumulation of bradykinin

(B) Accumulation of thiocyanate

(C) Depletion of thiol groups

(D) Haemolysis

Sodium nitroprusside is given by IV route and it can be converted into thiocyanate in the body which on accumulation may produce toxic effects like inhibition of thyroid function, weakness and nausea.