Pharmacology · single question

What is the mechanism of action of hydrochlorothiazide?

It blocks beta-1 adrenergic receptors
It inhibits sodium-chloride reabsorption in the distal convoluted tubule, acting as a diuretic
It blocks calcium channels
It inhibits angiotensin-converting enzyme

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Correct answer: B. It inhibits sodium-chloride reabsorption in the distal convoluted tubule, acting as a diuretic

A. Beta-1 blockade is the mechanism of metoprolol and atenolol.
B. CORRECT. Hydrochlorothiazide is a THIAZIDE DIURETIC. It inhibits the Na+/Cl- symporter in the DISTAL CONVOLUTED TUBULE, promoting sodium and water excretion, reducing plasma volume, and lowering blood pressure. Dental relevance: XEROSTOMIA is a common adverse effect; ORTHOSTATIC HYPOTENSION means raising the chair slowly; and HYPOKALEMIA plus HYPERGLYCEMIA, hyperuricemia, and hypercalcemia are metabolic effects to be aware of.
C. Calcium channel blockade describes amlodipine, nifedipine, verapamil, and diltiazem.
D. ACE inhibition describes lisinopril, enalapril, and ramipril.

Note: Thiazides SPARE calcium (they reduce urinary calcium), while loop diuretics WASTE it. That distinction shows up in bone questions.

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