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6mp and Allopurinol any information?

My son had been on 6mp since October. His initial dose was 50mg but they increase to 75 mg because he was not metabolizing enough of the drug. They just called with his blood work and they are switching back to 50mg with Allopurinol to help him metabolize it better. I have looked up the med and understand why but what other complications does this add to the mix? Why not just prescribe it this way in the first place? Thank you for any advice on this!


Super Moderator
I don't know that it adds complications as such but just helps to metabolise 6mp better. Lower doses and Allopurinol just work better for some people or for those that have side effects on higher doses of 6mp.

It not normally prescribed this way as most people are able to metabolise 6mp and don't suffer with side effects.

Dusty. xxx
It doesn't help metabolise it, but prevents it's breakdown, and hence elimination from the body.

From wikipedia:
Allopurinol inhibits xanthine oxidase, the enzyme that breaks down mercaptopurine. Those taking allopurinol (often used to prevent gout) are at risk for mercaptopurine toxicity. The dose should be reduced or allopurinol should be discontinued.

So, clever combination but potential difficulties with dose and toxicity balance.