Is it safe to mix them? It is not for myself nor is it for recreation. I have an uncle, who is taking codeine. He is taking it for bowel reasons, not for pain. He however has bad arthritis, and no medication seems to help him much. The other day (Thanks Giving(I live in Canada(our TG is at a different date than US))) I told him that a good Indica should keep him from noticing the pain(you still feel it, its just not painful) and suggested he try, he said fine and I said I'd get him some hashplant. That was totally irrelevant I didn't need to explain myself in such detail. Anyways, is it safe to mix them?

EDIT:
He just started the codeine a few days ago.