Antipsychotics still frequently prescribed for Parkinson patients

Despite FDA warnings, more than half of patients with Parkinson disease and psychosis were prescribed an antipsychotic in a new study.

Researchers used data from all Veterans Affairs facilities to assess trends in antipsychotic prescribing between 2002 and 2008. The study included 2,597 patients with Parkinson disease and psychosis and a comparison group of 6,907 patients with dementia and psychosis but not Parkinson disease. Results were published in the July Archives of Neurology.

In 2008, 50% of the patients with Parkinson disease and psychosis were prescribed an antipsychotic, a rate that was unchanged since 2002. Over the course of the entire study, quetiapine was the most frequently prescribed drug (66% of treated patients). The use of quetiapine increased over the course of the study, the researchers noted, even though all three placebo-controlled trials of the drug in Parkinson disease psychosis have been negative. Aripiprazole also increased in popularity, becoming the third most prescribed antipsychotic in these patients in 2008, even though research has shown poor tolerability, the authors said.

Almost 30% of treated patients received risperidone or olanzapine as their antipsychotic, and 7% got a high-potency typical antipsychotic. The study authors noted that typical and conventional antipsychotics are not recommended for use in patients with Parkinson disease because of the potential to exacerbate parkinsonism. The only drug that has demonstrated efficacy for the treatment of psychosis in these patients is clozapine, which was prescribed to fewer than 2% of the patients. Study authors noted several possible reasons for the low use, including the lengthy application process required to prescribe the drug, potential adverse events, and monitoring requirements.

They observed several other associations in the prescribing data. Patients diagnosed with Parkinson disease and dementia were more likely to receive antipsychotics than those without the conditions (despite FDA warnings about an association between the drugs and mortality in dementia patients), and younger Parkinson patients were particularly likely to be treated with antipsychotics.

The authors did note several limitations of their study, including that it may not be generalizable outside of the Veterans Affairs system. They called for additional research into the causes and effects of antipsychotic drug use in Parkinson patients.