Although first approved to treat schizophrenia, new antipsychotic medications are increasingly being prescribed for a host of other uses, even when there is little evidence they work, U.S. researchers said on Friday.

The drugs, known as “atypical antipsychotics,” have quickly eclipsed older-generation or “typical” antipsychotics and are increasingly used to treat conditions like bipolar disorder, depression and even autism.

“What we see is wide adoption for the use of these medications far beyond the evidence base to support it,” said Dr. Caleb Alexander of the University of Chicago and a consultant for IMS Health, a company that collects data on prescription drugs.

He said more than half of all atypical antipsychotic prescriptions written in 2008 were based on flimsy evidence.

“We’re talking millions of prescriptions a year for antipsychotics in settings where there is uncertain evidence to support them,” said Alexander, whose study appears in the journal Pharmacoepidemiology and Drug Safety.

The drugs are not harmless, Alexander said in a telephone interview. They can cause weight gain, diabetes and heart disease and are far more costly than the older antipsychotics, which cause disorders such as involuntary movements.

Atypical antipsychotics accounted for more than $10 billion in U.S. retail pharmacy drug costs in 2008 - nearly 5 percent of all prescription drug spending.

They include Johnson & Johnson’s Risperdal, known generically as risperidone; Eli Lilly and Co’s Zyprexa or olanzapine; Bristol-Myers Squibb and Otsuka Pharmaceutical Co’s Abilify or aripiprazole; and AstraZeneca’s Seroquel or quetiapine.

For the study, the team analyzed results of a physicians’ survey conducted by IMS Health to determine which antipsychotics were being used and for what condition.

They found that antipsychotic treatment nearly tripled to 16.7 million prescriptions written in 2008 from 6.2 million in 1995. During that period, prescriptions for first-generation antipsychotics fell to 1 million from 5.2 million.

Although first approved for schizophrenia, antipsychotic drugs are also used to treat psychoses, bipolar disorder, delirium, depression, personality disorders, dementia and even autism. Although some of the atypical drugs have won U.S. regulatory approval for some of these uses, doctors are also prescribing the drugs for unapproved uses.

To assess the evidence for these so-called off-label indications, the team used effectiveness ratings from a drug compendium called Drugdex.

They found that antipsychotic use for indications that lacked Food and Drug Administration approval more than doubled to 9 million prescriptions in 2008 from 4.4 million prescriptions 1995, representing about $6 billion in spending nationwide.

Dr. Gregory Simon of the Group Health Research Institute, who was not part of the study, said he was especially worried about the increased use of antipsychotic drugs for bipolar disorder and depression.

“For bipolar disorder, we have no evidence that the atypical antipsychotics are safer or more effective than alternative treatments. They are certainly much more expensive. But use of the atypical antipsychotics has grown rapidly, displacing treatments that are less expensive and more well-established,” Simon said in an e-mail.

For depression, the drugs are used to augment antidepressant therapy, but Simon said there are several other options, including switching to another antidepressant.

“Again, we have no evidence that adding an atypical antipsychotic is more effective than those other options, and it is the most expensive choice,” he said.

Dr. Randall Stafford of Stanford University School of Medicine, who worked on the study, blames marketing by drug companies and a tendency for doctors to think newer is better.

“Physicians want to prescribe and use the latest therapies - and even when those latest therapies don’t necessarily offer a big advantage, there’s still a tendency to think that the newest drugs must be better,” he said in a statement.

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By Julie Steenhuysen

CHICAGO