Azathioprine and Mercaptopurine

DO THEY AFFECT FERTILITY AND PREGNANCY?

Tell your doctor if you are thinking of becoming pregnant or find you are pregnant, and either you or your partner are taking azathioprine or mercaptopurine. Manufacturers’ guidelines state azathioprine and mercaptopurine should not be given to patients who are pregnant or likely to become pregnant in the near future. But many experts now feel these drugs can be taken during pregnancy where benefits are judged to outweigh risks. Most doctors recommend women to continue with their azathioprine or mercaptopurine while pregnant as there may be a greater risk to the baby if the woman stops her treatment and as a consequence becomes unwell.

A recent study has shown that mothers taking thiopurines during pregnancy is not associated with low birth weight or birth defects, although links have been made with premature births and anaemia at birth. Long-term studies show children exposed to thiopurines in the uterus have normal mental and physical development and no increased risk of infections.

With regard to fathers taking thiopurines, one study suggests azathioprine and mercaptopurine do not reduce sperm quality, but some manufacturers say mercaptopurine may occasionally cause temporary reductions in sperm counts. However, since active IBD has been associated with abnormal sperm quality, taking medications to maintain remission may help conception.

Older studies reported a slight increase in birth defects in the children of fathers taking thiopurines. However, larger more recent studies have not found this to be the case.

For both men and women, it is important to talk to your IBD team about the risks and benefits for you, so that decisions can be made based on your own individual health.

Regarding contraception, azathioprine and mercaptopurine can reduce effectiveness of intrauterine contraceptive devices (such as the coil) so you might want to consider alternative forms of family planning.

WHAT ABOUT BREASTFEEDING AND IMMUNOSUPPRESSANTS?

If you wish to breastfeed consult your IBD team. The drug manufacturers do not recommend breast feeding by women taking azathioprine or mercaptopurine. However, many experts have suggested that mothers taking thiopurines can breastfeed so long as babies are full-term, healthy and they do not have weakened immune systems. Studies have shown very little active drug is secreted into breast milk and that the drug is not detectable in the babies’ blood.

There is no evidence of harm in children whose mothers have breastfed while on these drugs.

References