As far as I know, LDN, hasn't been approved for use in the treatment of Crohn's in Canada. I believe the drug is prescribed for what's it's intended use is. I'm not sure if a GI would prescribe it though.
My daughter was diagnosed Feb. 19/07, (13 yrs. old at time of diagnosis), with Crohn's of the Terminal Illium. Initially, 9 weeks of Prednisone, currently taking 2000mgs of Pentasa.