Hi Kelly,
Has your GI talked about the different meds you are taking respectively starting? If not I think you should ask to be walked through all the currently standard medication used for Crohn's, the why behind them, side effects and benefits.
On your current medication: Pentasa is a medication that works superficially and helps some Crohn's patients, but not many. Many Docs still prescribe it though, many GIs have, however, also dropped it entirely for Crohn's (it is still an important drug for UC patients and can help Crohn's patients - it normally has little in terms of side effects).
Prednisolone is definitely the most powerful drug for short term use to fight inflammation for Crohn's. it has all kind of short term and long term side effects. It is tapered off as you do in small steps. If your symtoms come back you should talk to your GI and up again, then taper down again.
6-mecaptopurine or 6-mp is an immunosuppressive drug and one of two types of drugs used for long term Crohn's management (the other being biologics like remicade or humira). I have been on azathioprine which is basically the same drug as 6mp since 2003 (with a 2 year hiatus) and never experienced any side effects, but most are very rare including hair loss which is a very rare side effect - more commonly people 10-20% of the patients don't tolerate 6-mp right away and of those who tolerate and for those for which 6-mp works the serious side effects that are most commonly mentioned in literature are an in increase in certain cancer types (but not a worrysome increase, for lymphomia it's 4 in 10,000 compared to 2 in 10,000 in the general population), a higher likelihood of infections (again in rare cases severe infections) and problems for your liver (that is why you do regular blood tests to check for problems that may start to develop). most people accept the side effects because they are rare and if 6mp helps you with getting healthy the benefits far outweight any risks. A whole forum sub group is dedicated to these drugs
http://www.crohnsforum.com/forumdisplay.php?f=64
My suggestion would be, altough this right now must seem to be a complete information overload, to just read as much as you can (on the internet and on this forum) to really get informed about the drugs you are taking, but also all the other things you can and should do to manage your Crohn's. when it comes to managing it, good information is truly power.
All the best,
Alex