Indications for Folinic Acid

[futuredoctor10]

A UW question asks for the treatment of MTX-induced folate-deficiency macrocytic anemia and answers included both folic acid and folinic acid. The correct answer is folinic acid which is more potent, but the answer explanation specifically says this is for chronic methotrexate use and folate-deficiency anemia.

So for general folate-deficiency anemia (e.g. from alcoholism, malnutrition) do you use folic acid or folinic acid?

I know folic acid is used with methotrexate to prevent the anemia from developing (prophylaxis) which UW mentions as well. Interesting that the treatment once the anemia develops is different.

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[Smashingdude]

Well, from my understanding of Step1 Biochem, Methotrexate will block Folate conversion to its active form, irrespective of the length of usage (acute vs chronic). The main reaction what MTX works on is actually:

Folate(inactive)->Di hydro folate reductase->TH4 (active)

MTX will block DHFR, and thus you wont have the active form, thereby preventing DNA synthesis. So, to prevent its toxicity, there is no point in giving Folate, since it will be blocked. You should give Folinic acid, which is an analogue of the TH4 i.e. give directly the active form. This is also called the 'Leucovorin rescue'

For general folate deficiency, you use Folate since the enzyme DHFR is working and not inhibited by anything.

Hope that helps.