A 900-mg daily dose of gabapentin was associated with significant decreases in hot flash severity and frequency, but a 300-mg daily dose of the drug was not, results from a randomized, double-blind, placebo-controlled trial have found.
“We believe gabapentin can be added to the list of nonhormonal agents for the control of hot flashes in women with breast cancer, and the effects of doses higher than 900 mg/day merit further study,” wrote the investigators, led by Kishan J. Pandya, M.D., of the University of Rochester (N.Y.).
In a study funded by the National Cancer Institute, he and his associates randomized 420 women with a mean age of 55 years to receive placebo, 300 mg/day of gabapentin, or 900 mg/day of gabapentin.
The women, the majority of whom were white, were enrolled at 18 different sites of the university's community clinical oncology program. They recorded the severity level of hot flashes and 10 other symptoms in a 1-week self-report diary at baseline and during the fourth and eighth weeks of treatment (Lancet 2005;366:818–24).
Posttreatment analysis revealed that the reduction in hot flash severity score was only 15% for those in the placebo group, compared with 31% for those in the 300-mg/day gabapentin group and 46% for those in the 900-mg/day gabapentin group. The differences between groups were statistically significant, but only the 900- mg/day dose of gabapentin was associated with significant decreases in hot flash frequency and severity.
No differences were observed among the three treatment groups with respect to the 10 other symptoms, suggesting that gabapentin was well tolerated.
“Our study was designed to test the intervention for 8 weeks; therefore, we cannot comment on long-term use of gabapentin,” the investigators wrote.
While the drug's mechanism of action in the reduction of hot flashes in women with breast cancer remains unclear, the investigators speculate that “upregulation of the gabapentin binding site could be involved in the hypothalamus as a result of estrogen withdrawal, leading to increased activity of the neurotransmitters in the hypothalamus.”
Gabapentin is approved for the treatment of epileptic seizures but it is also used for the treatment of migraines, restless legs syndrome, and bipolar disorder.
Pfizer Inc. provided the gabapentin and placebo used in the study.