The US Food and Drug Administration is telling the manufacturers of antiepileptics to add a warning to their labels that use increases risk of suicidal thoughts and behaviours, however a boxed warning will not be a requirement.

The FDA's move is based on the agency's review of 199 clinical trials of 11 antiepileptic drugs which showed that patients receiving antiepileptic drugs had almost twice the risk of suicidal behaviour or thoughts (0.43%) compared to placebo (0.24%). This difference was about one additional case of suicidal tendency for every 500 patients treated with the drugs instead of placebo.

The agency added that four of the patients who were randomised to receive one of the antiepileptic drugs committed suicide, whereas none in the placebo group did. However the FDA pointed out that “results were insufficient for any conclusion to be drawn about the drugs' effects on completed suicides and the biological reasons for the increase in the risk are unknown.

"Patients being treated with antiepileptic drugs for any indication should be monitored for the emergence or worsening of depression, suicidal thoughts or behaviour, or any unusual changes in mood or behavior,” said Russell Katz, director of neurology products in the FDA's Center for Drug Evaluation and Research.

The FDA is following the recommendations of a joint meeting of advisory committees made in July which saw panellists vote 14-4 against suggestions previously made by the agency that the aforementioned drugs should carry a black box warning. However the milder warnings will extend to the whole class of medications and the drugmakers involved will need to develop a medication guide.

The warning covers 21 drugs, including Pfizer’s Neurontin (gabapentin) and Lyrica (pregabalin), GlaxoSmithKline’s Lamictal (lamotrigine), UCB’s Keppra (levetiracetam) and Vimpat (lacosamide), Johnson & Johnson’s Topamax (topiramate) and Abbott Laboratories’ Depakote (valproate).