Dental OSCE (Objective Structured Clinical Examination) Practice Exam

What is the mechanism of action of Triamterene, a potassium-sparing diuretic used for hypertension?

1. Excrete potassium

2. Conserve potassium

3. Decrease sodium retention

4. Increase calcium absorption

The correct answer is: Conserve potassium

Triamterene acts as a potassium-sparing diuretic primarily by inhibiting sodium reabsorption in the distal nephron of the kidneys. This mechanism leads to the conservation of potassium, which is crucial for maintaining electrolyte balance. Unlike other diuretics that promote the excretion of potassium, triamterene works by blocking the epithelial sodium channels (ENaC) in the distal convoluted tubule and collecting duct. Consequently, while sodium is excreted in the urine, potassium is retained, making triamterene unique among diuretics. The other options do not accurately reflect the action of triamterene. For instance, while decreasing sodium retention might sound plausible, triamterene conserves potassium as it reduces sodium absorption, rather than just decreasing sodium retention in a more general sense. There is no direct action related to calcium absorption with triamterene, making that option incorrect as well. Therefore, understanding the mechanism of how triamterene leads to potassium conservation helps highlight its role in treating conditions like hypertension without causing hypokalemia, a common side effect of other diuretics.