NeoMercazole Use In Pregnancy & Lactation

Carbimazole crosses the placenta but, provided the patient's dose is within the standard range, and the patient's thyroid status is monitored, there is no evidence of neonatal thyroid abnormalities. Studies have shown that the incidence of congenital malformations is greater in the children of patients whose hyperthyroidism has remained untreated than in those to whom treatment with carbimazole has been given. However, very rare cases of congenital malformations have been observed following the use of carbimazole or its active metabolite methimazole during pregnancy. A causal relationship of these malformations, especially choanal atresia and aplasia cutis congenita, to transplacental exposure to carbimazole and methimazole cannot be excluded. Therefore, the use of carbimazole in non-pregnant women of childbearing potential should be based on individual risk/benefit assessment (see Precautions). Cases of renal, skull, cardiovascular congenital defects, exomphalos, gastrointestinal malformation, umbilical malformation and duodenal atresia have also been reported. Therefore, carbimazole should be used in pregnancy only when propylthiouracil is not suitable. If NeoMercazole is used in pregnancy the dose of NeoMercazole must be regulated by the patient's clinical condition. The lowest dose possible should be used, and this can often be discontinued three to four weeks before term, in order to reduce the risk of neonatal complications. The blocking-replacement regimen should not be used during pregnancy since very little thyroxine crosses the placenta in the last trimester.
NeoMercazole is secreted in breast milk and, if treatment is continued during lactation, the patient should not continue to breast-feed the baby.