Intramuscular olanzapine vs. intramuscular short-acting antipsychotics: safety, tolerability and the switch to oral antipsychotic medication in patients with schizophrenia or acute mania

Background: This study compared the safety, tolerability and switch to oral medication in patients with bipolar disorder or schizophrenia who received intramuscular (IM) olanzapine or other IM antipsychotics for the treatment of acute agitation. Methods: Patients (N = 2011) from 15 countries participated in this prospective, observational, non-interventional study. Inpatients requiring treatment with at least one IM injection of a short-acting antipsychotic were assessed at baseline and within 7 days after the first IM injection. Treatment groups comprised: (i) patients prescribed IM olanzapine at baseline; and (ii) patients prescribed any other IM antipsychotic medication at baseline. Outcome measures included: treatment-emergent adverse events, concomitant psychotropic medication and the time taken to switch to oral medication. Results: Fewer patients in the IM olanzapine group experienced an adverse event than patients in the other IM antipsychotic group (34.4% vs. 46.2%, p < 0.001). The most frequently reported adverse events in both groups were: sedation, Parkinsonism, disturbance in attention, akathisia, dystonia and orthostatic hypotension. Fewer patients in the IM olanzapine group used anticholinergics (13.9% vs. 42.5%, p < 0.001) or anxiolytics/hypnotics (47.6% vs. 51.6%, p = 0.023). Patients in the IM olanzapine group switched to oral medication earlier than patients in the other IM antipsychotic group (median time = 46.5 vs. 48.0 h, p = 0.009). Conclusions: These findings suggest that IM olanzapine may have a favourable impact on individual patients. However, the high rate of oral concomitant medication used throughout the study limits these findings from being associated with IM olanzapine alone.