Previous animal studies as well as pilot trials in humans have suggested that tamoxifen might be effective in treating bipolar-related mania.
For the new study, 66 men and women with bipolar disorder and currently in a manic state, or mixed states that included mania, were randomly assigned to take 40 to 80 milligrams of tamoxifen a day or a placebo for up to three weeks.
Participants were also given up to 5 milligrams a day of the sedative lorazepam as needed.
Fifty patients completed the study.
At the end of three weeks, participants taking tamoxifen had significantly lower scores on tests used to measure the severity of mania, with 48 percent of them citing a reduction of at least half in their mania scores.
Those in the placebo group had slightly increased mania scores, and only 5 percent experienced a reduction of at least half in their mania scores.
Twenty-eight percent of those in the tamoxifen group reached the cut-off scores for remission from mania, compared to none in the placebo group, the researchers said.
Another expert was intrigued by the results.
"I found the study very interesting -- not that it necessarily indicates that tamoxifen is the best, newest, greatest drug for bipolar, although that's possible," said Dr. Andrew Kolodny, vice chair of psychiatry at Maimonides Medical Center in New York City. He said the study's real importance may lie in the fact that "it points towards a mechanism for the disease. The particular role of a molecule is hard to find in psychiatry."
More information
The U.S. National Institute of Mental Health has more on bipolar disorder.
