<prompt> Centrally acting antihypeensive drugs are all EXCEPT: March 2004Alpha methyl dopaClonidineGuanabenzTrimethoprim  <response>: 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 formby competitively inhibiting the enzyme dihydrofolate reductase. 