Pregnancy warning for drugs – AJP


Two antithyroid drugs have seen their categories changed, with strong precautions issued for women of childbearing age and pregnant women

Healthcare professionals are advised that the pregnancy category for propylthiouracil and carbimazole is being moved from category C to category D after reports of post-marketing congenital anomalies following the use of these drugs.

Medications should not be prescribed to women of childbearing age unless – in the opinion of the doctor, the potential benefits outweigh the possible risks – according to a medication safety update from the TGA.

Propylthiouracil is an antithyroid drug indicated for the total treatment of hyperthyroidism or for the treatment of the patient with thyrotoxicosis before surgery or radioactive iodine therapy, marketed in Australia under the trademark PTU.

Carbimazole is also an antithyroid drug indicated for hyperthyroidism. It is used as a definitive therapy in the induction of permanent remission in primary or secondary thyrotoxicosis.

Carbimazole, which is also used in preparation for a thyroidectomy before and after radioactive iodine treatment, is marketed in Australia under the brand name Neo-Mercazole.

While reviewing a safety signal relating to birth defects for propylthiouracil and carbimazole, the TGA found that the current Australian PI documents for both drugs contained sufficient safety information in “Section 4.6 Fertility, pregnancy and lactation”.

In addition, the PI for carbimazole contains additional information on women of childbearing potential and pregnancy in “Section 4.4 Special warnings and precautions for use”.

However, the products were previously classified under pregnancy category C, which is defined as “drugs which, due to their pharmacological effects, have caused or may be suspected of causing harmful effects on the human fetus or newborn without. cause malformations. These effects can be reversible ”.

“As there have been reports of post-marketing birth defects following the use of these drugs, this category is no longer considered the correct categorization of pregnancy,” TGA said.

“Category D is defined as” drugs which have caused, are suspected of having caused or may cause an increased incidence of human fetal malformations or irreversible damage “and reflects the post-marketing experience of these drugs.”


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