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
True about Acetazolamide is ? 
Select and explain. 
A. Decreased GFR, B. Action similar to sulphonamide, C. It decreases Na, K, Glucose excretion, D. It causes metabolic alkalosi
A: Decreased GFR
Answer: A: Decreased GFR 
Explanation: Ans. is 'a' i.e., Decreased GFR o Acetazolamide decreases GFR. o Carbonic anhydrase inhibitors increase delivery of solutes to the macula densa by inhibiting proximal reabsorption. o This results in activation of TGF (tubulo-glomerular feedback mechanism), causing increased afferent aeriolar resistance and reduces renal blood flow (RBF) and glomerular filtration rate (GFR). About option 'b' o Dont get confused with option b, with answer of previous question. o Acetazolamide has structural resemblance to sulfonamide, but mechanism of action is different. Acetazolamide acts as diuretic by inhibiting carbonic anhydrase, whereas sulfonamides are primarily antimicrobials and act by inhibiting bacterial folate synthesis.