There is some evidence that the risk of haematological
toxicity may be increased in
renal transplant patients taking
azathioprine if they are also given
co-trimoxazole or
trimethoprim, particularly if both drugs are taken for extended periods. However, other evidence suggests that the drugs may be used together safely, and the combination is commonly used in practice.
Azathioprine is rapidly and extensively metabolised to mercaptopurine. Mercaptopurine is therefore expected to interact similarly.
Full blood count should be monitored if
azathioprine or mercaptopurine is used. If any abnormalities arise, consider this interaction as a possible cause.