MCQ on drugs acting on heart failure: Page-3

Here question indicates that we have to select the drugs that target both alpha and beta receptors. In another words, the drug may be either agonist or antagonist. Dobutamine is such a drug which even acts as β ₁ agonist still shows action on α ₁ and β ₂ receptors as agonist. Quite oppositely, Labetalol acts as antagonist but still on both α and β receptors. Phenoxybenzamine is a non-selective α-blocker that blocks both α1 and α2 but has no action on β receptors. Isoproterenol, on the other hand, acts mainly on β receptors with no action on α receptors.

Digoxin belongs to cardiac glycosides which has three important structural features viz. Sugar moiety, steroidal ring and lactone ring. Lactone ring is responsible for cardiac activity whereas sugar moiety is responsible for its transport. The activity of the drug will be lost if lactone ring is opened.

Carvedilol is a beta blocker with alpha blocking activity. It has no action on intracellular calcium levels in heart. Furosemide is loop diuretic that increases calcium excretion but has no direct action on heart. Digoxin inhibits Na ⁺/K ^+-ATPase pump thereby increases intracellular calcium levels within the heart. Finally, Verapamil is a calcium channel blocker that suppresses the influx of calcium into the cardiac muscle.

Verapamil is a calcium channel blocker that decreases force of contraction and hence contraindicated in heart failure.

Adenosine is a cardiac depressant and vasodilator which is not indicated in heart failure. It is a drug of choice in SVT. Glucagon increases cAMP in cardiac muscle and increases force of contraction. Digoxin is a cardiotonic which also increases force of contraction. Carvedilol is a both alpha and beta blocker that decreases cardiac work in heart failure.