WASHINGTON, Sep 13 (Reuters) The breast cancer pill tamoxifen helped treat the ''manic'' symptoms of bipolar disease, US government researchers said.
Although tamoxifen may be too dangerous a drug to take for bipolar disease, the findings may offer a way to design better drugs to treat it, the team at the National Institute of Mental Health said yesterday.
They tested tamoxifen because it blocks an enzyme called protein kinase C or PKC, which regulates activities in brain cells. PKC is thought to be over-active during the manic phase of bipolar disorder.
An estimated 6 million American adults have bipolar disorder, also known as manic depression. Patients have profound mood swings, from disabling depression to overwhelming excitement or severe irritability.
The symptoms sometimes are severe enough to require hospitalization and drugs that treat the manic symptoms take time to work and often have severe side effects. They include lithium, antipsychotics and anti-seizure drugs.
''People think of the depressive phase of this brain disorder as the time of risk, but the manic phase has its own dangers,'' said NIMH Director Dr. Thomas Insel.
''Being able to treat the manic phase more quickly would be a great asset to patients, not just for restoring balance in mood, but also because it could help stop harmful behaviors before they start or get out of control.'' Dr Husseini Manji and colleagues at NIMH tested 16 patients experiencing manic episodes, who got either tamoxifen or a placebo for three weeks.
By the end of the study, 63 per cent of the patients taking tamoxifen had reduced manic symptoms, compared with only 13 percent of those taking a placebo. Tamoxifen started showing benefits within five days, the researchers reported in the journal Bipolar Disorders.
Tamoxifen blocks some of the effects of the hormone estrogen and can raise the risk of endometrial cancer in women.
''We now have proof of principle. Our results show that targeting PKC directly, rather than through the trickle-down mechanisms of current medications, is a feasible strategy for developing faster-acting medications for mania,'' Manji said in a statement.
''This is a major step toward developing new kinds of medications.'' REUTERS KK KP1003