NEW YORK - Although doctors sometimes prescribe anti-seizure drugs to treat chronic pain in the vulva, just a handful of low-quality studies have examined the drugs' effects, according to a new review.
Based on these studies, "it's very difficult to make definitive statements on efficacy," said Dr. Raphael Leo, the study's author from the State University of New York at Buffalo. "Certainly, more investigation is warranted."
Still, "I think that there is promise" for the use of anti-seizure medications, he added.
Chronic pain in a woman's genitals, also called vulvodynia, affects as many as one in 12 women.
The underlying cause of the pain is not always known, so doctors often try a variety of treatment approaches to see what will work.
Those include topical creams to reduce pain, physical therapy, antidepressants and - in extreme cases - surgery to remove the painful tissue.
Anti-seizure medications, such as gabapentin (marketed as Neurontin), are also used to treat vulvodynia. One survey found up to two-thirds of doctors prescribe gabapentin for the condition.
"Unfortunately, there hasn't been much systematic investigation of an appropriate means of treatment," Leo told Reuters Health.
To see whether research supports the use of anti-seizure drugs, he collected the results of all studies testing these medications on women with the pain disorder.
He found nine reports, none of which met the criteria for a high-quality clinical trial.
In a "gold standard" medical trial, women would be randomly assigned to take the medicine or a drug-free placebo, with neither women nor the researchers knowing which pill each person was taking. This is called a double-blind, randomized controlled trial.
Instead, the studies Leo found used less rigorous research designs, including "open label" formats, where patients and doctors know which drug each participant is taking. He also found descriptions of people taking anti-seizure medications and reviews of patients' medical charts.
The medications studied included gabapentin, pregabalin, lamotrigine and carbamazepine, Leo wrote in The Journal of Sexual Medicine.
All of the studies showed that some women reported improvements in their symptoms after taking an anti-seizure drug.
For instance, one study that reviewed the medical charts of 147 women taking gabapentin found that symptoms completely went away in 67 per cent of patients. Most of the other patients showed no response.
"Definitely the open label studies have been encouraging," said Dr. Samantha Meltzer-Brody, director of the perinatal psychiatry programme at the University of North Carolina Center for Women's Mood Disorders.
"This may be a very useful treatment for some women, but until there are the gold standard, double-blind studies, there is a need for further scientific investigation," said Meltzer-Brody, whose study on lamotrigine was included in Leo's review.
Without high-quality clinical trials, doctors can't say for certain whether the drug is any better than a placebo, nor whether women would have had an improvement in symptoms on their own, without medication.
"Any sort of conclusions one draws from such non-experimental studies are quite limited," said Leo.
He said more research is needed on treatments for vulvodynia.
Until then, "we don't understand whether one should consider one particular form of therapy over another and who would respond best to what type of treatment."