<prompt> Which is an antimetaboliteCyclosporineMethotrexateEtoposideVinblastine  <response>: Ans. is b i.e. Methotrexate AntimetabolitesThese are synthetic analogues of normal metabolites related to components of DNA or of coenzymes involved in nucleic acid synthesis.They act by Competition i.e. they deceive or defraud bodily processes.Instead of the natural substrate they get themselves incorporated, forming dysfunctional molecules.These drugs act on the S phase of the cell cycle, thus only dividing cells are responsiveFolic acid analoguesPurine antagonistsPyrimidine antagonistst Methotrexate 6 mercaptopurine S fluorouracil Pemetrexed 6thioguanine Cytarabine 