Eight drugs used to treat schizophrenia and other psychotic illnesses may not work as well as doctors think they do, a new study suggests.
That's because some data regarding the drugs, known as second-generation antipsychotic drugs, have not been published, even though the trials were submitted to the Food and Drug Administration (FDA) before the drugs were approved.
All of the unpublished studies showed unfavorable results for the drug being tested — either the drug did not work better than a placebo, or it did not work better than a competing drug.
The findings matter because doctors use published studies to guide them in their decisions when writing prescriptions. If studies with negative results remain unpublished, doctors are getting incomplete information about the drug. Selectively publishing studies with positive results is known as publication bias.
While publication bias does not hugely change the view of how effective antipsychotic drugs are, it does cause problems, the researchers said.
Clinicians should be able to see the whole picture, said study researcher Erick Turner, of the Oregon Health & Science University in Portland, Ore. "They shouldn't just see the good news,", he said.
Turner and colleagues examined 24 drug trials that were conducted by companies seeking FDA approval before the drugs came to market. Together, the trials tested eight antipsychotic drugs for schizophrenia: aripiprazole, iloperidone, olanzapine, paliperidone, quetiapine, risperidone, risperidone long-acting injection and ziprasidone.
Four of the trials were unpublished, and three of these showed the drug being tested worked no better than placebo.
The researchers then compared these premarketing trials with the results of studies that had been published. Within the 20 published studies, some withheld information that would have made the drugs appear to be less effective. For instance, a premarket study testing iloperidone found that the drug worked less well than three competitor drugs, but this information was left out of the published information.
According to an informal review of the studies, risperidone and paliperidone had the most evidence of effectiveness, the researchers said.
When the researchers pooled the results of the premarket studies and the published studies and compared them, they found the antipsychotic drugs were only slightly more effective in published studies.
"The magnitude of publication bias found for antipsychotics was less than that found previously for antidepressants, possibly because antipsychotics demonstrate superiority to placebo more consistently," the researchers wrote in this week in the journal PLoS Medicine.
Still, the FDA is not as transparent as it could be with clinical trial information, making it available in a user-unfriendly format, and only once the drug is approved, Turner said. "If the agency fulfills its mission to increase transparency, the public health will surely benefit," the researchers said.
Pass it on: Publication bias can make a drug appear more effective than it really is.