Studies of azathioprine and 6-mercaptopurine for maintenance treatment of ulcerative colitis.
Six studies were reviewed and provide the best evidence we have. Study quality was mostly poor. The studies tested 286 people over the age of eighteen who had ulcerative colitis. The subjects received oral azathioprine or 6-mercaptopurine, placebo (fake pills) or standard maintenance treatment (mesalazine or sulfasalazine). The studies lasted for at least 12 months.
What is ulcerative colitis and could azathioprine and 6-mercaptopurine work?
Ulcerative colitis is a chronic inflammatory disorder of the colon. The most common symptoms of ulcerative colitis are bloody diarrhea and abdominal pain. Azathioprine and 6-mercaptopurine are thought to reduce inflammation by blocking the immune system.
What did the studies show?
The studies showed that azathioprine was better than placebo for maintenance treatment (i.e. preventing the disease from coming back once the patient has responded to treatment). Fifty-six per cent of patients treated with azathioprine were disease free after one year of treatment compared to 35% of patients who received placebo.
How safe are azathioprine and 6-mercaptopurine?
The drugs were generally well tolerated and side effects occurred infrequently. However serious side effects such as acute pancreatitis (an inflammation of the pancreas that causes severe abdominal pain - a 2% risk) and bone marrow suppression (failure to make normal blood cells - a 4% risk) can occur. Patients taking these drugs should be regularly monitored for evidence of effectiveness and side effects.
What is the bottom line?
Given the established effectiveness and safety of aminosalicylates (i.e. mesalazine or sulfasalazine) for the maintenance of remission in ulcerative colitis, azathioprine and 6-mercaptopurine cannot be recommended as first line treatment to prevent the disease from coming back. However, azathioprine may be an effective maintenance treatment for patients who have failed or cannot tolerate mesalazine or sulfasalazine and for patients who require repeated courses of steroids.