(Summary version version, Updated September 2021)
Olanzapine is a second generation (atypical) antipsychotic with a potent antagonism of serotonin 5-HT2A, 5-HT2C, dopamine D1-4, histamine H1 and alpha1-adrenergic receptors. It also has a moderate antagonism of muscarinic M1-5 receptors, as well as a weak agonism to GABA-A, BZD and beta-adrenergic receptors.
In the ED, olanzapine is frequently indicated as a first-line antipsychotic for acute agitation associated with psychiatric disorders (US FDA and EMA approved for agitation in individuals with schizophrenia and bipolar disorder)(7, 9). Agitation in the ED is a very complex situation that includes a variety of dissimilar scenarios with a wide range of therapeutic options. Many clinical guidelines have been proposed with substantial differences between them; as emergency physicians, it is of great importance to be familiarized with the available therapeutic arsenal for agitation, such as haloperidol, droperidol, benzodiazepines, propofol, ketamine, etc.
There are significant differences among first and second generation antipsychotics, and there is an abundant amount of literature available that compare olanzapine with haloperidol as well as other therapies to treat agitation. Clinically relevant data is summarized below:
Olanzapine vs haloperidol; extrapyramidal effects: olanzapine had a reduced risk of nearterm side effects such as dystonia or akathisia, with rates being less than 1%; 10 times less than haloperidol. (1, 2).
Olanzapine vs haloperidol; adequate sedation within 15 min: olanzapine showed better results (61% vs 42%)(6).
Olanzapine vs haloperidol; need of rescue medication: olanzapine needed less rescue medication (21% vs 33% in the entire encounter)(6).
Olanzapine vs haloperidol + benzodiazepine; sedation in 2 hours: either intervention showed similar results (3).
Olanzapine vs droperidol; time to sedation: no significant difference (16 min vs 17.5 min)(10).
Olanzapine vs droperidol; need of rescue medication: olanzapine needed more rescue medication (24% vs 17%)(10).
Olanzapine vs droperidol; extrapyramidal effects: olanzapine had a significantly lower risk (0.1% vs 6.1%)(10).
Therefore, olanzapine is currently recommended as the first-line antipsychotic for an agitated psychiatric adult patient (2). In the pediatric population it is considered to be safe and effective (8), but is not yet US-FDA nor EMA approved for agitation (7, 9).