A drug currently used to treat schizophrenia could also help millions of people with manic depression.

Results from a major clinical trial suggest quetiapine is an effective treatment for those with bipolar disorder.

The drug, which is manufactured by AstraZeneca, and sold under the brand name Seroquel, works well if it is used in combination with mood stabilising medication.

It might become another option for people who have bipolar disorder

Dr Tony Cleare, Institute of Psychiatry

Experts said the trial paved the way for the drug to be used as an alternative treatment for people with manic depression.

Professor Gary Sachs from Harvard Medical School in the United States who headed the study said the drug was more effective than some existing treatments.

Existing drugs

"Current treatment options for patients with bipolar disorder are limited. Commonly used therapies involving mood stabilisers are not effective for all patients and can be associated with troublesome side effects," he said.

"As a result patient compliance with treatment can be a real challenge. This is particularly critical in bipolar disorder since patients typically lead full lives with jobs to hold down and valuable relationships to maintain."

Professor Sachs added that the drug was effective in reducing symptoms of bipolar disorder.

"The results show not only that quetiapine is effective in treating bipolar disorder and the manic symptoms often associated with it, but also that more patients treated with quetiapine experienced a full resolution of their manic symptoms compared to patients taking mood stabilisers alone.

"This impressive efficacy combined with the excellent tolerability profile that quetiapine exhibited throughout the trial, suggest that it is an important and valuable new weapon in our fight against this problematic disease."

However, AstraZeneca will first have to seek regulatory approval to enable doctors to prescribe quetiapine to patients with the disorder.

Alternative

Nevertheless, Dr Anthony Cleare a senior lecturer at the Institute of Psychiatry in London and a consultant psychiatrist welcomed the results of the clinical trial.

He told BBC News Online: "The important thing is that for patients who are reporting side-effects from other medication this will provide an alternative.

"It might become another option for people who have bipolar disorder."

Bipolar disorder is a severe mental illness that affects more than 1% of the adult population.

This figure is starting to rise as more and more patients are being diagnosed properly. A high proportion of patients with the condition attempt suicide.

The results of the clinical trial were presented at the third European Stanley Foundation Conference on Bipolar Disorder in Freiburg in Germany.