Published: 6 June 2014


Reminder: Olanzapine depot and post-injection syndrome

Prescriber Update 35(2)
6 June 2014

Key Messages

  • Olanzapine pamoate depot injection carries a small risk of post-injection syndrome.
  • Patients must to be monitored for at least two hours after each dose.
  • Symptoms of post-injection syndrome include sedation, confusion, agitation, anxiety, aggressiveness, dizziness, ataxia and extrapyramidal symptoms.
  • In most cases, symptoms appear within one hour following injection and resolve within 24 – 72 hours.
  • Healthcare professionals are advised to discuss this potential risk with patients each time they prescribe and administer olanzapine pamoate depot injection.


Healthcare professionals are reminded that patients who receive olanzapine pamoate depot injection must be monitored for at least two hours after each dose1.

Olanzapine pamoate is an antipsychotic depot formulation for injection, designed to release olanzapine slowly from the intramuscular site. It is administered by deep intramuscular injection into the gluteal region every two to four weeks.

Post-injection syndrome has been estimated to occur after 0.07% of olanzapine depot injections and in approximately 1.4% of treated patients2. The syndrome is yet to be convincingly linked to depot antipsychotics other than olanzapine. Post-injection syndrome includes a range of signs and symptoms such as sedation and delirium that are consistent with olanzapine overdose. Other symptoms include dizziness, weakness, aggression, ataxia, hypertension and seizures. Extrapyramidal symptoms are also reported, such as tremor, dystonia, akathisia, and tardive dyskinesia.

Initial signs and symptoms of post-injection syndrome appear within one hour following injection1. In most cases full recovery is expected to occur within 24-72 hours after injection. There is no specific reversal agent for olanzapine depot injection and treatment of post-injection syndrome is management of the symptoms.

The Centre for Adverse Reactions Monitoring (CARM) has received 14 reports of reactions following olanzapine pamoate injection that suggested a post-injection syndrome had occurred. Patients experienced reactions including sedation, ataxia, slurred speech, blurred vision, confusion, agitation, and extrapyramidal symptoms. The time to onset of symptoms ranged from ‘immediate’ to one hour following injection. The dose and interval between doses varied considerably. Most patients required overnight observation in hospital.

Cases of post-injection syndrome have also been reported internationally. The FDA issued an alert in June 2013 over three unexplained deaths in patients who had received olanzapine depot injection. The following link provides more details:

Healthcare professionals are advised to discuss the potential risk of post-injection syndrome with their patients prior to administering each dose of olanzapine pamoate.

Please report any adverse reactions to the CARM. The following link provides more information about how to report:


  1. Eli Lilly and Company (NZ) Limited. 2013. Zyprexa Relprevv Data Sheet. 31 January 2013. URL: (accessed 12 May 2014).
  2. Novakovic V, Adel T, Peselow E et al. 2013. Long-acting injectable antipsychotics and the development of postinjection delirium/sedation syndrome (PDSS). Clinical Neuropharmacology 36:59-62.
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