Gabapentin No Boost to Venlafaxine for Hot Flashes


ATLANTA — Adding gabapentin to venlafaxine does not augment the effectiveness of the antidepressant to control hot flashes, according to a study presented at the annual meeting of the American Society of Clinical Oncology.

Separate, previously reported, randomized, controlled trials have shown that both gabapentin and newer antidepressants, such as venlafaxine, are each significantly more effective than placebo in preventing hot flashes. However, in this study, which combined the two, no potentiation of relief was noted, said Dr. Charles Loprinzi, codirector of the Mayo Clinic Cancer Center's research program in cancer prevention and control in Rochester, Minn.

Vasomotor symptoms tend to be severe in breast cancer survivors because their estrogen supply is suddenly interrupted, and they may also be taking agents, such as tamoxifen, that are known to cause hot flashes. In addition, chemotherapy can cause abrupt menopause in a premenopausal woman, Dr. Loprinzi said in an interview.

The anticonvulsant gabapentin has been shown to reduce hot flashes when taken at 900 mg/day, compared with placebo. Similarly, venlafaxine (75 mg/day) has been shown to decrease hot flash episodes significantly more than placebo.

Dr. Loprinzi and his colleagues reasoned that it might be beneficial to add gabapentin to the regimen of women who continued to experience hot flashes despite receiving venlafaxine therapy.

In a randomized 4-week study involving 113 women, one group of 57 patients continued on the antidepressant and added gabapentin to their regimen; the second group of 56 patients stopped taking venlafaxine when they started on gabapentin.

The majority of the women had a history of breast cancer and had been treated with tamoxifen, raloxifene, or an aromatase inhibitor within 4 weeks of entry into the study. A minority of the study population did not have breast cancer, but did not wish to take hormonal therapy. Women in the gabapentin group had an average age of 55 years (ranging from 39 to 72); those in the combination therapy group had an average age of 58 years (ranging from 41 to 81). At baseline, the women were suffering from a mean of 14 bothersome hot flashes a week. The investigators found that when gabapentin was added to venlafaxine, “there was about a 50% reduction in hot flashes, but the reduction was the same whether the women were on gabapentin alone, or on gabapentin and an antidepressant,” Dr. Loprinzi said.

There was a 50% reduction in hot flashes whether gabapentin was used alone or in combination with an antidepressant. DR. LOPRINZI

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