First Aid error or USMLE World error...

[alexndra]

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Hey... I have a quick question for everyone. USMLE World says that Methotrexate is a G1 phase specific antimetabolite while the First Aid says it is S phase specific. Which is it??

How about Bleomycin and Etoposide, as these are different too.

Thanks.

 

[SkylineMD]

Methotrexate should be S-phase specific because it is playing a role in DNA synthesis by inhibiting DHF-reducatase --> needed to regenerate THF which then allows thymidylate synthase to convert dUMP to dTMP

 

[nasdr]

from our pharm lecture notes: VP-16 (etoposide) and VM-26 are cell cycle phase specific agents. Cells in the S and G2 phases of the cell cycle are most sensitive to VP-16 and VM-26. i guess it makes sense since DNA topoisomerase II is mainly active in the S phase, and microtubules are not affected at the doses given.

 

[KNightInBlue]

Methotrexate hits the G1/S phase transition - so you could make the argument for either case

did the UW questions have both G1 and S phases in the answer choices?


If I absolutely had to choose, I'd go with S-phase specific



p.s. maybe you can email the UW ppl with the discrepancy and see what they say.....