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Mercaptopurine and Allopurinol - Advice?

Hey guys,

I posted recently about going back on to Azathiprine from my surgery 7 months ago and long story short... it's killing off my white blood cells and making me feel horrible so after yet more blood tests they've told me I need to go onto Mercaptopurine and Allopurinol instead.

Can anyone give any advice about the drugs as I've never been on them. I'm also trying to get pregnant too and despite my consultant saying that Aza was okay, I'm wary of these two.

If you've been on them, how did they effect you? It's Allopurinol i'm most worried about because I know that Mercaptopurine is just like Aza so I know what to expect.



Super Moderator
I wouldn't worry too much about the Allopurinol in itself, it is a drug that widely used to treat gout, but it has a special relationship with the thiopurines - Imuran (Azathioprine) and 6-mercaptopurine (6mp)

With those that have the type of issues you do with the thiopurines Allopurinol is added as it inhibits one of the enzymes responsible for inactivating 6-mercaptopurine (the active form of azathioprine). What this means in a nutshell is, when you add Allopurinol to 6mp you reduce the amount of 6mp that is required. I can't recall what the reduction is for 6mp but for Imuran you reduce to a quarter of the dose with Allopurinol, so 100mg would become 25mg. The idea being that you can tolerate the benefits of the thiopurines without the adverse reactions you are now experiencing.
@DustyKat thank you so much for your advice. That's exactly what the IBD nurse but I wanted some honest advice from people that know what's it like to take it.

I see that you're a Mum and have Crohn's too... Do you have any advice about getting pregnant and being pregnant with Crohn's? I'm slightly terrified that I won't be able to get pregnant or that my meds will cause issues.