contra-indications and warnings for azathioprine
Last reviewed 01/2018
- pregnancy and lactation - limited data suggests that if a woman becomes pregnant while taking a thiopurine for inflammatory bowel disease, continuing treatment does not increase the risks of pregnancy complications or congenital abnormalities. However, it seems prudent not to start a thiopurine if a woman plans to become, or is, pregnant, nor should women breast feed- while taking a thiopurine (1).
- gross renal or hepatic disease
- blood dyscrasias
- care with allopurinol. Reduce the azathioprine dose to one quarter of the original
thiopurine S-methyl transferase (TPMT)
- assessment of TPMT is useful in the treatment
of patients with thiopurine drugs such as azathioprine, mercaptopurine and 6-thioguanine
- 0.3 % of the population do not have this enzyme and can build up toxic
levels of the active metabolites. Another 10% have a medium activity and may also
need a lower dose than other patients
- the strategy of determining TPMT activity in all patients prior to initiating treatment with azathioprine could help to minimize the risk of myelotoxicity, as patients with intermediate TPMT activity had fourfold more risk than high TPMT activity patients (2)
- 0.3 % of the population do not have this enzyme and can build up toxic
levels of the active metabolites. Another 10% have a medium activity and may also
need a lower dose than other patients
- assessment of TPMT is useful in the treatment
of patients with thiopurine drugs such as azathioprine, mercaptopurine and 6-thioguanine
Check the summary of product characteristics for detailed information.
Reference:
- Drug and Therapeutics Bulletin (2002), 39 (12), 91-95.
- Gisbert JP et al. Thiopurine Methyltransferase (TPMT) Activity and Adverse Effects of Azathioprine in Inflammatory Bowel Disease: Long-Term Follow-Up Study of 394 Patients. Am J Gastroenterol. 2006 Oct 6