So for a while now I have been off Asacol HD 800 mg. My usual routine was to take 2 pills in the morning when I woke up and 1 pill before bed (the logic I hear is that if you have side effects you would get them in the night-which is why you take the lower dosage before bed). Speaking of side effects my primary doctor told me that since Asacol is aspirin based it is possible to get ringing in the ears (which I did have from time to time). Asacol always for some reason gave me cramps (which is odd since Asacol is designed for inflammatory bowel disease!). This would be like taking an anti-depressant and then becoming more depressed.
The very first study I could find was this one from 1983 in the Journal of Gastroenterology which showed that improved the symptoms of 72% of patients with Crohn's disease (only 18 patients were in the study though). It seems as if in the 1990's there were studies that showed that Asacol was effective in treating Crohn's. In 1992 this study showed that Asacol helped patients who didn't have ileal involvement. In 1993 this trial showed that 78% of patients maintained remission when Asacol was used alone. This study from 1994 showed that oral mesalamine (Asacol) was effective in helping achieve a partial or complete remission in 60% of patients as opposed to 22% of patients in the placebo group. In 1995, this double blind study showed that Asacol had a "moderate but significant benefit to preventing relapse in Crohn's in remission; this occurred only in patients with small bowel involvement or those older than 30 years". This 1998 study showed that 5-ASA treatments were helpful after surgery (in resection) for maintenance of Crohn's disease
Then this study from 2007 showed that oral mesalazine right after surgery prevented endoscopic recurrence in Crohn's over a 2 year period and it was estimated that it prevented 39% of all recurrences.
Recently however, the data doesn't support the notion that Asacol helps people with Crohn's. This study found that Humira after an intestinal resective surgery was effective in preventing endoscopic and clinical recurrence of Crohn's. This study showed a small subgroup of Crohn's patients may be helped from 5-ASAs (Asacol). This study shows a benefit for Asacol for patients with ulcerative colitis but the evidence for Crohn's is not clear. Perhaps Asacol has become less effective over time, Crohn's has possibly changed, or some other reason.
From what I understand Asacol is very effective for people with ulcerative coltis (I don't have a medical background to explain why this is), however for me at least I did get cramps from taking Asacol at night usually. I now feel better after getting of it. Also the fewer drugs you are taking the fewer risks for not only short term but potential long term side effects substantially decreases. I would be pretty happy if I didn't have to take Asacol for a while. Time will tell though.