SIDE EFFECTS OF AZATHIOPRINE (IMURAN) and 6-MERCAPTOPURINE (6-MP)

While azathioprine and 6-MP are effective medicines for those with IBD, they also come with side effects that can limit their usefulness.

The most common early side effects are:

• Nausea, and sometimes vomiting
• Increased abdominal pain with pancreatitis <<link—N4K pancreatitis>>
• Anemia
• Low white cell count
• Increased diarrhea
• Joint pain
• Liver damage

Both 6-MP and azathioprine are prescribed based on the patient's weight. In fact, azathioprine is changed to 6 -MP in the liver. But 6-MP is sometimes given at a relatively higher dose. As a result, low white counts and liver damage seem to occur more often with 6-MP than azathioprine.

Later Side Effects

The early side effects can show up may stop some patients from using them in the beginning. But it's the side effects that can show up later that causes more concern.

• Skin cancers can develop. Using an effective sun screen routinely for protection, avoiding the sun when possible and regular skin examinations may help to prevent some of these cancers
• Lymphomas do seem 3-5 times more common than in the general population. In the study that looked at this in almost 20,000 individuals with IBD, the risks began after a year on the medication. Men were 2 times more likely than women, with men under 30 years of age at the greatest risk, though all those older than 50 years of age were the next highest group for risk. 
• Liver damage can also show up later

As with side effects from medications, some patients are more prone to those side effects than others. At least with azathioprine and 6-MP, we can determine the potential for some of those side effects with genetic testing, drug monitoring and from what we've learned after using them for so many decades.

Most doctors who treat IBD are well aware of both the benefit and risks of Azathioprine and 6-MP. They prescribe it because they think that one of these will be the right medicine for you. However, you may wish to discuss any concerns with them, if you are on the medication, have been on it in the past or if its use is being considered.