Campaigners say young women of childbearing age should have been warned about the epilepsy drug as long ago as 1974

Warnings to young women who might become pregnant that the epilepsy drug sodium valproate could cause birth defects and developmental problems in their babies could have been made public more than 40 years ago, according to campaigners.

“These warnings could have and should have been given in 1974,” said Catherine Cox from the Fetal Anti-Convulsant Syndrome Association at a public hearing of the European Medicines Agency, which is conducting a risk assessment of the drug. “However, there was a deliberate decision not to publish them.”

Regulators knew about the risks when they were considering licensing sodium valproate for the control of seizures in epilepsy. But documents from 1973 show they thought telling patients “could give rise to fruitless anxiety”.

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A “Dear Doctor” letter warned health professionals: “This compound has been shown to be teratogenic in animals, meaning it could harm the human foetus.”

But the then Committee on Safety of Medicines said the warning should “not (go) on the package inserts, so that there would be no danger of patients themselves seeing it”.

The EMA’s risk assessment committee will decide what extra measures should be taken to safeguard young women who might become pregnant and their children from sodium valproate. The drug, used to treat epilepsy but also bipolar disorder and migraine, has long been controversial.

While many campaigners would like an outright ban for women of childbearing age, doctors say there are some for whom it is the only drug that will control their epileptic seizures. Campaigners estimate that up to 20,000 children in the UK may have been harmed.

Babies whose mothers are given the drug during pregnancy run a 11% risk of birth defects and a 40% risk of developmental problems. Karen Keely, from the Organisation for Anti-Convulsant Syndrome in Ireland, told the EMA that her three sons, Lee, Lorcan and Harry, all have birth defects after she was prescribed Epilim, one of the brand names of sodium valproate.

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“Two of my three boys require life-long care and will never live a normal life, will never be able to have children or get married,” she said. “The effects of sodium valproate have been unbearable.

“I have been mourning my children since the day they came into my life and I’m determined to not let this injustice happen to other families in the same way that it has happened to mine.”

Women are still unaware of the risks of the drug, even after a “toolkit” was produced last year for doctors and patients by the Medicines and Healthcare Products Regulatory Agency, which replaced the Committee on the Safety of Medicines, with the help of stakeholders.

But Clare Pelham of the Epilepsy Society said a survey last month of 2,000 young women with the condition found that 68% did not know about it, which was a slight increase on the 64% from the years before when the toolkit had only just been introduced.

She called on the inquiry to make warnings to women mandatory, rather than voluntary. The health secretary, Jeremy Hunt, should require GPs to review any woman on the drug face to face every 12 months. “It is a very straightforward measure,” she said.