MONDAY, Feb. 11 (HealthDay News) -- The epilepsy drug oxcarbazepine (Trileptal) does not seem to prevent migraines, as once thought, a new study finds.

Migraines affect more than 28 million Americans, and certain epilepsy drugs have been shown to be effective in preventing these severe headaches. For this reason, many assumed that oxcarbazepine would also work against migraines.

However, "the results of this trial do not support preliminary data which had suggested oxcarbazepine was effective in preventing migraine," lead researcher Dr. Stephen D. Silberstein, from Thomas Jefferson University in Philadelphia, said in a statement. "While several epilepsy drugs have been used for decades to prevent migraine, oxcarbazepine did not prevent migraine in this study despite it being shown to be safe and well-tolerated."

In the trial, 170 men and women took oxcarbazepine or placebo daily for almost five months. All the people in the study suffered from three to nine migraine attacks a month. Silberstein's team found no difference between people taking oxcarbazepine or placebo in the number of migraines they suffered during the study.

The report appears in the Feb. 12 issue of Neurology.

"It's good to do these types of double-blind studies to assess effectiveness of medications," said Dr. Walter J. Molofsky, chairman of the Department of Neurology at Beth Israel Medical Center in New York City.

"Since some antiepileptics are useful against migraine headaches, it would be reasonable to assume that Trileptal would work, too. This is an example of what is necessary to prove the presence or absence of benefit," Molofsky said.

The three epilepsy drugs that have been shown to prevent migraines, topiramate, divalproex and gabapentin, do so through several mechanisms. One mechanism is the regulation of the neurotransmitter called GABA. However, oxcarbazepine appears not to affect GABA activity. It is possible that epilepsy drugs need to regulate GABA to prevent migraine, Silberstein noted.

Another expert agreed that this drug is not likely to prevent migraine.

"This is a study done by a group of experts in the field following all the usual standards of clinical research, so the findings can be accepted as valid," said Dr. Ellen Drexler, director of the Headache Center at Maimonides Medical Center in New York City. "The results are not that surprising, as drugs with related mechanisms of action such as carbamazepine or phenytoin have never been found to be efficacious for migraine prophylaxis."

The study was paid for by Novartis Pharmaceuticals Corp., maker of oxcarbazepine. Just last week , the U.S. Food and Drug Administration warned that 11 epilepsy drugs, including oxcarbazepine, might boost the risk of suicide among users.

More information

For more information on migraines, visit the U.S. National Library of Medicine.