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
Centrally acting antihypeensive drugs are all EXCEPT: March 2004 
Select and explain. 
A. Alpha methyl dopa, B. Clonidine, C. Guanabenz, D. Trimethoprim
D: Trimethoprim
Answer: D: Trimethoprim 
Explanation: Ans. D i.e. Trimethoprim Trimethoprim is structural analogue of the pteridine poion of dihydrofolic acid but, unlike sulfonamides, it blocks the conversion of dihydrofolic acid to tetrahydrofolic acid (active form)by competitively inhibiting the enzyme dihydrofolate reductase.