This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diuretics and Antidiuretics, Subject name: Pharmacology
One of the following diuretics does not require its presence in the tubular lumen for its pharmacological effects: 
Select and explain. 
A. Thiazide diuretics, B. Loop diuretics, C. Carbonic anhydrase inhibitors, D. Aldosterone antagonists
D: Aldosterone antagonists
Answer: D: Aldosterone antagonists 
Explanation: Ans. (D) Aldosterone antagonists(Ref: KDT 8/e p634)*Most of the diuretics act from the luminal side of membrane in the nephron.*Thiazides, loop diuretics, carbonic anhydrase inhibitors and epithelial Na+ channel blockers (e.g. amiloride and triamterene) are secreted in the proximal tubules through organic anion/cation transport process.*Osmotic diuretics reach the lumen of proximal tubules via glomerular filtration.*Aldosterone antagonists like spironolactone do not act through luminal side rather they act from basolateral side of the membrane. Therefore, these agents do not require access to the tubular lumen.