Hi Sam, and welcome

There are several medications that can be taken for P, the most common being Methotrexate (or MTX) and Cyclosporin.
They are basically immuno-suppressors, i.e. they shut down part of your immune system. They're mainly regarded as drugs against cancer or for people who have had a transplant to suppress rejection of the transplanted organ, but P being an immune deficiency, they can be used against P as well...
They can have some nasty side effects as well, most notably liver and kidney damage.
I have never been on either of them, but a few people here have, and they will be able to tell you much more than I

In the meantime, you can always check up on previous "talks" about the subject here, if you like

:
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LoginMaybe you could also try to talk to your doc about treatments like Infliximab or Eternacept - they basically work the same way, but have a much "narrower function area", so they have less nasty side effects - and some people have had really good results with them

There's a bit about those here:
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LoginAll the very best of luck to you, and when you have questions, feel free to ask

Take care,
Des