Doctors continue to prescribe antipsychotic drugs to their patients with Parkinson's disease and psychosis, despite "black box" warnings from the FDA linking them to increased risk of death among patients with dementia, a study shows.
A black box warning is the strongest drug warning issued by the FDA.
"My sense is that the black box warnings don't factor into decision making," says study researcher Daniel Weintraub, MD, an associate professor of psychiatry at the University of Pennsylvania.
The study is published in the Archives of Neurology.
The black box warning for antipsychotics says the drugs are associated with an increased risk of death for those with dementia, which is common among people diagnosed with Parkinson's. Some commonly prescribed antipsychotics also worsen symptoms of Parkinson's.
Risperdal (risperidone) and Zyprexa (olanzapine), for example, are two such drugs, and neither has been shown to be very effective. Yet according to the study, nearly 30% of patients with Parkinson's and psychosis take them.
Clozaril (clozapine), the only drug known to be both effective and well-tolerated for treating psychosis in Parkinson's patients, is prescribed to less than 2% of those with the disease.
"The gold standard treatment is also one of the most impractical treatments," says neurologist Hubert Fernandez, MD, a Parkinson's specialist at the Cleveland Clinic's Center for Neurological Restoration.
Because of a rare but potentially deadly side effect of the drug, patients on clozapine must have their blood monitored at regular intervals. That burden discourages many doctors from prescribing the medication.
The alternatives, however, are far from ideal. Abilify (aripiprazole), the third most commonly prescribed antipsychotic, is poorly tolerated by Parkinson's patients. And the most popular drug, Seroquel (quetiapine), has failed to show positive results in three studies.
"Quetiapine is the No. 1 choice without clear evidence that it's effective," says Weintraub.
Lack of treatment alternatives
The researchers examined Department of Veterans Affairs patient records from fiscal year 2008, comparing the rates of antipsychotic drug prescriptions among two groups: 2,597 patients with Parkinson's disease and psychosis with and without dementia and 6,907 patients with dementia and psychosis but without Parkinson's disease; 97.3% of the patients studied were men.
"More men are diagnosed with Parkinson's, and men are more likely to develop dementia," says Weintraub.
An estimated 60% of Parkinson's patients will experience some form of psychosis during their illness, according to the study. Weintraub and colleagues found that half of all patients with Parkinson's and psychosis were treated with antipsychotic medications.
Perhaps their most striking finding was that overall prescription rates had not decreased compared to 2002, despite the black box warning that was issued in 2005. To Fernandez, the reason is simple: doctors have few options to offer.
"This study is very important because it highlights the problem that clinicians face," says Fernandez. "The problem is it's not very easy to treat, and few patients will be completely treated."
Weintraub agrees that treatment choices are quite limited, but he hopes that his study will encourage doctors to make greater use of clozapine and to be more conservative in prescribing other antipsychotics.
"If they are to be used, they should be used only for a period of time rather than indefinitely, as negative effects may accrue from exposure," says Weintraub.
By Matt McMillen
Reviewed by Louise Chang, MD