Evaluation of haloperidol decanoate initiation dosing in inpatients with serious mental illness.

Introduction: Manufacturer labeling for haloperidol decanoate recommends an initial dose of 10 to 20 times the daily oral dose; however, significant heterogeneity in dosing practices exists. The purpose of this medication use evaluation was to assess initial haloperidol decanoate dosing in psychiatric inpatients. Methods: An institutional review board-exempt retrospective chart review was conducted using data from University of California Health Data Warehouse (UCHDW) from June 1, 2014, to June 1, 2024. Inpatients diagnosed with schizophrenia or schizoaffective disorder aged 18 years or older receiving an initial dose of haloperidol decanoate were included. Patients on dual antipsychotics or those without oral haloperidol within 24 hours before decanoate administration were excluded. The primary outcome was the proportion of patients receiving 10 to 20 times the oral haloperidol dose as per the manufacturer's package insert. Secondary outcomes included dosing characterization and incidence of extrapyramidal symptoms. Descriptive statistics were employed. Results: A total of 147 eligible patients were included, with a mean age of 49 years; 62% of participants were male. The mean oral dose of haloperidol before decanoate initiation was 20.7 mg, and the mean initial dose of haloperidol decanoate was 178 mg. The primary outcome was observed in 47.6% of patients. Of those who received doses outside of the recommended range, 41.5% received a dose less than 10 times the oral haloperidol dose, while 10.9% received a dose exceeding 20 times the oral dose. Conclusion: Fewer than half of the patients evaluated received an initial dose of haloperidol decanoate as recommended by the manufacturer's labeling. These findings underscore the need to further investigate clinician attitudes, comfort, and knowledge on haloperidol decanoate prescribing.