Case Series Profile of Olanzapine Post-Injection Delitrium/Sedation Syndrome

Abstract

Olanzapine pamoate is an intramuscular depot injection for the treatment of schizophrenia. Approximately 1.4% of patients develop a serious adverse event called Post Injection Delirium/Sedation Syndrome (PDSS); characterised by drowsiness, anticholinergic and extrapyramidal symptoms. The objective is to investigate olanzapine PDSS presentations including clinical features and treatment approach. This is a retrospective review of olanzapine PDSS patients from three toxicology units and the NSW Poisons Information between 2017 and 2022. Adult patients were included if they had intramuscular olanzapine then developed PDSS criteria. Clinical symptoms, treatment, timing and length of symptoms were extracted into a preformatted Excel database. There were 18 patients included in the series, with a median age of 49 years (IQR: 38-58) and male predominance (89%). Median onset time post injection was 30 minutes (IQR: 11-38). PDSS symptoms predominate with drowsiness, confusion and dysarthria. Median length of symptoms was 24 hours (IQR: 20-54). Most common treatment included supportive care without any pharmacological intervention (n=10), benzodiazepine (n=4) and benztropine (n=3). In one case, bromocriptine and physostigmine followed by oral rivastigmine were given to manage anti-dopaminergic and anti-cholinergic symptoms respectively. This proposed treatment combination could alleviate some of the symptoms. In conclusion, this case series supports the characterisation of PDSS symptomology predominantly being anti-cholinergic with similar onset (<1 hour) and duration (<72hours). A combination of bromocriptine and physostigmine followed by rivastigmine is proposed to manage PDSS if patients develop severe dopamine blockade or anti-cholinergic delirium.