BACKGROUND:The management of neuropsychiatric symptoms, including psychosis, in Parkinson's Disease (PD) is complicated by the fact that treatment with antipsychotics can worsen the movement disorder, which may necessitate changes to antiparkinsonian medications. OBJECTIVES:The objectives of this study were to determine what antipsychotics are prescribed to residents in long-term care with PD and document subsequent changes in levodopa dosage. METHODS:A retrospective cohort study using administrative health database information from Ontario, Canada, was conducted. PD diagnostic codes were obtained from the Ontario Health Insurance Plan (physician diagnostic codes) and the Canadian Institute of Health Information (hospitalization discharge diagnoses). The Ontario Drug Benefit database provided information on the use of antiparkinsonian medications and antipsychotics. Residents diagnosed with PD in long-term care were included if they were treated with stable doses of levodopa monotherapy and received a new prescription for an antipsychotic. The type of antipsychotic and the changes in levodopa dosage were determined. RESULTS:There were 479 residents who met inclusion criteria. The prescribed antipsychotics were quetiapine (n = 192; 40 %), risperidone (n = 185; 39 %) and olanzapine (n = 81; 17 %), and only 21 (4 %) received a prescription for a typical antipsychotic. The first levodopa dosage change was a dose reduction in 469 (98 %) patients, and a dose increase in ten (2 %) patients. CONCLUSIONS:Many PD patients in long-term care are treated with potentially inappropriate antipsychotic medications. However, there is no evidence that this treatment results in a prescribing cascade that leads to inappropriate increases in levodopa dosage.