Since Crohn's Disease is in part an auto-immune disorder Prednisone is often used to suppress the immune system response.  The drawback of Prednisone is that it weakens the immune system making it easier for the patient to contract sickness or infections.  Prednisone is a prodrug, that is it is not active until it is metabolized, that is converted by the liver into the active ingredient Prednisolone and a steriod.

Methylprednisolone

Methylprednisolone is a variant of Prednisolone the active ingredient in the prodrug Prednisone.  There are many possible side effects of Corticosteroids because these types of drugs affect numerous biological systems in humans and animals.  If you are prescribed any corticosteroid you should never abruptly stop taking the drug, because your adrenal system becomes dependent on the drugs ability to replace the natural corticosteroids by your glands.  Many severe effects may occur as a result including death.  A patient should always consult a physician before stopping a Corticosteroid and the drug doses should be tapered as the patient's  Adrenal system gradually becomes accustomed to producing its own hormones again.