This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Furosemide mechanism of action in LVF is: September 2010 
Select and explain. 
A. Inhibitor of Na-K-Cl ion sympo, B. Aldosterone antagonist, C. Mercurial derivative, D. Carbonic anhydrase inhibitor
A: Inhibitor of Na-K-Cl ion sympo
Answer: A: Inhibitor of Na-K-Cl ion sympo 
Explanation: Ans. A: Inhibitor of Na-K-Cl ion sympo Like other loop diuretics, furosemide acts by inhibiting the Na-K-2C1 sympoer in the thick ascending limb of the loop of Henle. The action on the distal tubules is independent of any inhibitory effect on carbonic anhydrase or aldosterone; it also abolishes the coicomedullary osmotic gradient and blocks negative as well as positive free water clearance.