One of the oldest available anti-seizure medications, ethosuximide, is the most effective treatment for childhood absence epilepsy, a new study says.

The study group compared three medications typically used to treat the most common childhood epilepsy syndrome, childhood absence epilepsy, which is characterised by frequent non-convulsive seizures that cause the child to stop what he or she is doing and stare for up to 30 seconds at time.

OHSU Doernbecher Children's Hospital is one of 32 comprehensive paediatric epilepsy centres selected to participate in this landmark clinical trial as part of the NIH Childhood Absence Epilepsy Study Group.

'Much of our scientific understanding of childhood epilepsy care today comes from historical experience or studies involving adult patients with related, but not identical, conditions,' explained Colin Roberts, M.D., OHSU Doernbecher's principal investigator for the study, assistant professor of pediatrics and neurology, and director of OHSU Doernbecher's Pediatric Epilepsy Program.

Prior to this study, there was no definitive evidence on which drug worked best.

'This study is an important milestone in our understanding of childhood absence epilepsy. Never before have we been able to document in such a comprehensive, scientific fashion the best options to treat children with this condition.'

The study group enrolled 453 children newly diagnosed with childhood absence epilepsy from July 2004 to October 2007. Study participants were randomly assigned to ethosuximide, valproic acid or lamotrigine. Drug doses were incrementally increased until the child was seizure-free.

After 16 weeks of therapy, the researchers found ethosuximide and valproic acid were significantly more effective than lamotrigine in controlling seizures, with no intolerable side effects. They also determined ethosuximide was associated with significantly fewer negative effects on attention.

The initial outcomes were published in this week's New England Journal of Medicine.