Post injection syndrome

NSW Health has issued a safety notice on post-injection syndrome related to olanzapine long-acting injections (LAI). Post-injection syndrome (PIS) can arise due to the inadvertent intravascular injection of olanzapine. This syndrome presents with signs of overdose such as sedation or delirium and may also include extrapyramidal symptoms, dysarthria, ataxia, or convulsions. While recovery from PIS is expected to occur within 24 to 72 hours, NSW Health has reported a death associated with PIS that was not recognised.

The onset of PIS symptoms ranges from immediate to up to five hours post-injection. A large observational study reports that around 91% of cases occur within the first hour of injection and 96% occur within two hours of injection. The product information recommends an observation period of at least two hours following each administration of olanzapine LAI. This observation period should be extended as appropriate for any patients who exhibit signs or symptoms of PIS. Patients should also be advised not to drive for the rest of the day and to remain vigilant for PIS symptoms after leaving the healthcare facility.

Post-injection syndrome is a rare event thought to occur in around 0.07% of olanzapine LAI administrations. It is not dose-related and may occur in patients who have previously received olanzapine LAI without incident. The syndrome has not been reported with other long-acting antipsychotic injections.


  1. Detke HC, MCDonnell DP, Brunner E, Zhao F, Sorsaburu S, Stefaniak V, et al. Post-injection delirium/sedation syndrome in patients with schizophrenia treated with olanzapine long-acting injection, I: analysis of cases. BMC Psychiatry. 2010; 10:43.
  2. Meyers KJ, Upadhyaya HP, Landry JL, Chhabra-Khanna R, Falk DM, Rao BS, et al. Postinjection delirium/sedation syndrome in patients with schizophrenia receiving olanzapine long-acting injection: results from a large observational study. BJPsych Open. 2017; 3(4): 186-92.
  3. Zyprexa Zelprevv® (Olanzapine Pamoate Monohydrate) Australian approved product information. West Ryde: Eli Lilly. Approved March 2009.

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