Case report: increased patient response to intramuscular haloperidol decanoate following a change in needle length

Intramuscular (IM) injection is a commonly used administration route for a variety of medications. Determining the optimum needle length for administration of IM formulations based on individual patient variables has not been extensively reported in patients receiving antipsychotic medication via IM administration.

The patient, a 23-year-old African American female diagnosed with schizophrenia, was referred to a community-based treatment program following multiple inpatient admissions. At age 19, she began experiencing psychiatric symptoms that resulted in assault and incarceration. Treatment included separate trials of haloperidol and fluphenazine decanoate formulations with minimal success reported. At the time of evaluation, she was experiencing constant positive psychiatric symptomatology. Oral haloperidol was started. Haloperidol decanoate 150 mg by IM injection using a 1.5-inch needle was added and titrated to 350 mg IM over 11 months. Auditory hallucinations continued. Following refusal of a haloperidol level, the physician changed to a 2-inch needle for decanoate injections. Noticeable and continued slow improvement of her psychotic symptoms resulted.

Needle length may be of new importance to practitioners. If anticipated results of IM antipsychotic medication administration are not realized, practitioners are urged to consider patient variables, notably the amount of adipose tissue in the administration area.