The safety of anticonvulsant drugs is in the spotlight again after a cohort study published in the Journal of the American Medical Association found that some of these medicines might be linked with a higher risk of suicide.

The findings indicate that certain anticonvulsants, including Pfizer's Neurontin (gabapentin) and Novartis' Trileptal (oxcarbazepine), could put newly-treated patients at a higher risk of suicide, suicidal acts and violent deaths, placing a further shadow over the safety of these widely-used drugs.

The researchers, headed by a team from Brigham and Women's Hospital in Boston, looked at data on patients aged 15 years and older who began taking anticonvulsant therapy between July 2001 and December 2006, in order to assess the risk associated with individual drugs.

Overall, out of 97,620 new episodes of treatment with an anticonvulsant, the researchers identified 26 completed suicides, 801 attempted suicides and 41 violent deaths, and an exploratory analysis found that the risk of suicidal acts was higher in patients who took Neurontin, GlaxoSmithKline’s Lamictal (lamotrigine), Trileptal, Cephalon’s Gabitril (tiagabine) and Abbott Laboratories’ Depakote (valproate) compared to those taking Johnson & Johnson’s Topomax (topiramate).

The incidence of completed suicides, attempted suicides, and violent deaths for anticonvulsants used in at least 100 treatment episodes ranged from 6.2 per 1000 person-years for primidone to 34.3 for Trileptal, the data show.

However, the study was not large enough to draw any deeper conclusions on the scale of risk between these drugs. The risks were “pretty much even” among these medicines, and “it's not easy to draw conclusions about which one is the most risky”, researcher Elisabetta Patorno told Reuters.

But according to Ewald Horwath, professor of psychiatry and behavioural sciences at the University of Miami Miller School of Medicine, the study’s findings may be somewhat misleading.

He said it failed to place enough weight on why patients were being treated with these drugs in the first place, and pointed out that many were taking the anticonvulsants for bipolar disorder and depression, illnesses which are themselves “associated with higher suicide rates,” reports HealthDay News.

However, this is not the first time anticonvulsants have been linked to suicide, and back in 2008 the US Food and Drug Administration ordered manufacturers to add a warning to product labels on an increased risk of suicidal thoughts and behaviours.