anemia with phenytoin

[DrPak]

USMLERx sez the anemia is because of Vitamin B12 levels going down. Goljan's RR sez it's because folate absorption is interfered with. Which is it?

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[39094]

USMLERx sez the anemia is because of Vitamin B12 levels going down. Goljan's RR sez it's because folate absorption is interfered with. Which is it?

I believe it's both. I think it interferes with both B12 and folate absorption and also screws with folate metabolism.

 

[Hernandez]

Harrisson's states

"A number of drugs antagonize folate by mechanisms that are poorly understood but are thought to involve an effect on absorption of the vitamin by the intestine. In this category are the anticonvulsants phenytoin, primidone, and phenobarbital. Megaloblastic anemia induced by these agents is mild."​

Now there are several references to B12 soprtion problems from phenytoin, however, with a person with a normal dietary history prior to starting phenytoin, they should have an adequate supply of B12, as the average person has a 6-9 year supply of b12 in stores. So in cases where the phenytoin has been used for a short term, the answer should be folate, for long term cases, probably both.

That's my understanding anyways.

 

[DrPak]

Harrisson's states

year supply of b12 in stores. So in cases where the phenytoin has been used for a short term, the answer should be folate, for long term cases, probably both.

That's my understanding anyways.​

Yep, that sounds correct.​