Gabapentin Effective for Hot Flushes From Androgen Deprivation Therapy in Men With Prostate Cancer

Zosia Chustecka

July 03, 2007

July 3, 2007 — Gabapentin ( Neurotin, Pfizer) was effective at reducing hot flushes occurring with androgen deprivation therapy (ADT) in men with prostate cancer, in a study reported at the recent American Society for Clinical Oncology (ASCO) 43rd Annual Meeting, in Chicago, Illinois. "To my knowledge, this is the only nonhormonal agent that has been shown to work in these patients in a placebo-controlled trial," lead research Charles Loprinzi MD, from the Mayo Clinic in Rochester, Minnesota, told Medscape.

Based on the information available so far, gabapentin "is a reasonable option to offer" to men with prostate cancer who are suffering hot flushes from ADT, Dr. Loprinzi commented, although he pointed out that this would be an off-label use of the drug. Gabapentin is approved by the Food and Drug Administration for use in epilepsy and postherpetic neuralgia, but the dose used for these indications (3000 – 3600 mg daily), is much higher than the dose used in the trial for hot flushes (300 – 900 mg).

There are few other options available for the treatment of hot flushes from ADT in men with prostate cancer, Dr. Loprinzi commented. Estrogen and progestogen have been used, but these hormones carry attendant risks, he pointed out. The antidepressant venlafaxine ( Effexor, Wyeth) has shown some efficacy for hot flashes in women, but the data in men are preliminary and come from a pilot study, not from a placebo-controlled trial. Another agent, clonidine, appears to be effective in women but not in men, he added.

Hot flushes can be a very disruptive adverse effect of ADT, having a large impact on well-being, Dr. Loprinzi commented. To be eligible for the clinical trial with gabapentin, men had to experience "bothersome" hot flushes (at least 14 per week), but many reported far more than this, Dr. Loprinzi noted: 45% of participants reported having 4 to 9 hot flushes each day, and 40% reported more than 10 per day.

The trial involved 223 men with prostate cancer on ADT, and gabapentin was used at 3 doses (300 mg once daily, 300 mg twice daily, or 300 mg thrice daily) and compared with placebo over a treatment period of 4 weeks. The highest dose of gabapentin (900 mg daily) significantly reduced the frequency of hot flushes, Dr. Loprinzi noted. The mean reduction in hot-flush frequency was 41% with 900-mg gabapentin vs 20% on placebo ( P = .02), while the median decrease in frequency was 44% with gabapentin vs 22% with placebo ( P = .004).

"We believe this is a real difference, and we conclude that gabapentin results in a moderate decrease in hot flushes," Dr. Loprinzi commented. He pointed out that these results are an average, and in some patients the effect of the drug "can be quite substantial."

Commenting on this paper during a "highlights-of-the-day" session at the ASCO meeting, Charles Shapiro, MD, from Ohio State University Medical Center, in Columbus, said: "This is an important study, and I predict that when this paper comes out — and it is due to be published soon — it will change clinical practice." Dr. Shapiro noted that the adverse effects of ADT can be quite severe, and there are no effective nonhormonal treatments for this group of men. He also mentioned that gabapentin has already proved to be effective in relieving hot flashes in women; a recent study suggested it was as effective as estrogen, as reported by Medscape.

American Society for Clinical Oncology 43rd Annual Meeting: Abstract 9005. Presented June 3, 2007.


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