Question

A hypertensive patient Mr. Zee already receiving a drug 'X' to control his blood pressure was prescribed a tricyclic antidepressant. This resulted in the abolition of the antihypertensive action of 'X'. Which of the following drug could be 'X'.

• A. Enalapril
• B. Clonidin
• C. Atenolol
• D. Diltiazem

Answer 1

The Correct Option is B

The question involves understanding the interaction between a blood pressure medication and a tricyclic antidepressant, resulting in the loss of antihypertensive effects. Let's analyze the given options to determine which drug, when combined with a tricyclic antidepressant, could lead to this scenario:

1. Enalapril: Enalapril is an ACE inhibitor that lowers blood pressure by inhibiting the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. Tricyclic antidepressants do not directly interact in a way that negates the effect of ACE inhibitors.
2. Clonidine: Clonidine is an alpha-2 adrenergic agonist that works by decreasing sympathetic outflow from the central nervous system, thereby reducing blood pressure. Tricyclic antidepressants can inhibit the uptake of norepinephrine and interfere with the action of drugs like Clonidine. This interaction can lead to the loss of Clonidine's antihypertensive efficacy, which aligns with the scenario given in the question.
3. Atenolol: Atenolol is a beta-blocker that reduces blood pressure by decreasing heart rate and cardiac output. Although tricyclic antidepressants can increase heart rate and cause orthostatic hypotension, they do not typically negate the effect of beta-blockers in the manner described in the question.
4. Diltiazem: Diltiazem, a calcium channel blocker, inhibits calcium ions from entering the "excitable" cells of the heart and blood vessels, lowering blood pressure. The interaction with tricyclic antidepressants does not directly lead to a complete loss of antihypertensive action like with Clonidine.

Based on the analysis above, Clonidine is the correct choice for drug 'X' as it is known to have its antihypertensive action abolished when a tricyclic antidepressant is prescribed due to interference with its pharmacodynamic effects. The antidepressant's impact on norepinephrine reuptake antagonizes Clonidine’s mechanism of action, thereby abolishing its effectiveness.