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Pregnancy paracetamol warning

Doctors urge women to use lowest effective dose for shortest possible time

Mark Gould

Thursday, 21 May 2015

Following publication of a study* that suggests that prolonged use of paracetamol may reduce testosterone in unborn baby boys, doctors are urging pregnant women with symptoms of pain and fever to use the lowest effective dose of paracetamol for the shortest possible period of time.

The study, published by the University of Edinburgh in Science Translational Medicine today, tested the effect of a typical daily dose of paracetamol on testosterone production in mice. Results found no effect on testosterone production following 24 hours of paracetamol treatment. However, after seven days of exposure, the amount of testosterone was reduced by 45%. The authors of the study recommend that expectant mothers should follow existing guidelines that the painkiller should be taken at the lowest effective dose for the shortest possible time.

Dr Sadaf Ghaem-Maghami, Chair of the Royal College of Obstetricians and Gynaecologists Scientific Advisory Committee said that paracetamol is one of the most common medicines used to reduce a high temperature and ease pain and is used routinely during all stages of pregnancy.

She said that while the study was "a robust piece of research", it is important to note that it was carried out in animal models and it is not possible to translate the findings into a recommendation regarding what would be safe or unsafe in pregnant women.

Additionally, the mice were not pregnant but in a ‘pregnancy state’ which was induced by a hormone and human foetal testicular tissue which was grafted onto them.

“Further research needs to be conducted into how paracetamol may affect testosterone levels as well as examining the long-term developmental effects on testosterone production."

Professor Maureen Baker, Chair of the Royal College of GP, reiterated Dr Ghaem-Maghami's advice to pregnant women: “During pregnancy, women can have symptoms of pain and fever, just like anyone else, and paracetamol is very effective at managing these. But as with any drug, it is best to err on the side of caution and follow the guidance – in the case of paracetamol, to take the lowest possible dose, for the lowest possible time."

She added that existing evidence shows that, in the main, paracetamol is a safe drug for the majority of patients. "But this study – and other recent studies – call this into question and it is important that we take new research into account and shape updated guidelines for healthcare professionals in the best interests of all patients.”

And she said that pregnant women who have been taking paracetamol to ease discomfort – either as prescribed by their doctor or self-medicated – should not panic as a result of this research. "But if they are concerned about taking the drug regularly, over a long period of time they should make a non-urgent appointment with their GP, or visit their local pharmacist.”


* Sander van den Driesche, et al. Prolonged exposure to acetaminophen reduces testosterone production by the human fetal testis in a xenograft model. Sci Transl Med 20 May 2015: Vol. 7, Issue 288, p. 288ra80. DOI: 10.1126/scitranslmed.aaa4097

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