Which of the following is a potassium sparing drug: September 2005, March 2013
First, the core concept here is about diuretics and their effects on potassium. Potassium-sparing diuretics are those that don't cause potassium loss. They work by either blocking aldosterone or inhibiting sodium reabsorption in the distal tubule.
The correct answer is likely to be a drug like spironolactone or eplerenone, which are aldosterone antagonists. Also, amiloride and triamterene are potassium-sparing by inhibiting sodium channels in the distal nephron.
Now, why the other options are wrong. If there were options like thiazides or loop diuretics, those are potassium-wasting. Thiazides inhibit sodium reabsorption in the distal convoluted tubule, leading to potassium excretion. Loop diuretics act on the ascending limb of the loop of Henle and also cause potassium loss. ACE inhibitors and ARBs can actually increase potassium levels but aren't potassium-sparing in the diuretic sense.
Clinical pearl: Remember that potassium-sparing diuretics are often used with thiazides or loop diuretics to prevent hypokalemia. Spironolactone is also used in heart failure and hypertension due to its aldosterone-blocking effect.
So the correct answer would be one of the potassium-sparing diuretics. Since the options aren't provided, the explanation is based on general knowledge. The user needs to know that the key drugs here are spironolactone, eplerenone, amiloride, and triamterene.
**Core Concept**
Potassium-sparing diuretics are medications that promote sodium and water excretion without causing potassium loss. They act on the distal nephron to antagonize aldosterone (e.g., spironolactone) or inhibit sodium channels (e.g., amiloride/triamterene), preserving renal potassium reabsorption.
**Why the Correct Answer is Right**
Spironolactone is a **potassium-sparing diuretic** that competitively inhibits aldosterone at mineralocorticoid receptors. Aldosterone normally stimulates sodium reabsorption and potassium excretion in the collecting ducts. By blocking this, spironolactone reduces sodium retention and prevents potassium loss, making it a classic potassium-sparing agent.
**Why Each Wrong Option is Incorrect**
**Option A:** Thiazide diuretics (e.g., hydrochlorothiazide) cause **hypokalemia** by increasing potassium excretion in the distal convoluted tubule.
**Option B:** Loop diuretics (e.g., furosemide) induce **potassium wasting** via the ascending limb of the loop of Henle, leading to hypokalemia.
**Option C:** ACE inhibitors (e.g., lisinopril) **increase potassium levels** indirectly by reducing aldosterone but are not classified as potassium-sparing diuretics.
**Clinical Pearl / High-Yield Fact**
Spironolactone is the **prototypical potassium-sparing diuretic** and is often combined with thiazides or loop diuretics to counteract hypokalem