182 Unintentional Overdose on Long-Acting Injectable Risperidone

Abstract

Study Objectives

Understand the mechanism and pharmacokinetics involved in an unintentional overdose of injectableantipsychotic medication; identify how to transition between long acting injectable antipsychotics; formulate steps to ensure patient safety in an event of an unintentional overdose of injectable antipsychotic

Method

Review of a case study involving a 47-year-old male, with history of schizoaffective disorder and previous episodes of loss of consciousness of unknown etiology, who was admitted to the inpatient psychiatry unit at UConn Health John Dempsey Hospital for stabilization of psychotic symptoms and monitoring of unintentional overdose after initially being admitted to the ICU. He was found unconscious at home following a period of days where he self-injected four of 37.5mg Risperidone injections (estimated 150mg) along with limited adherence to prescribed oral clozapine, doxepin and lorazepam. He reported self-injecting additional medication to treat paranoia, auditory, visual and olfactory hallucinations. In the ICU, he was evaluated by Toxicology and Neurology for loss of consciousness thought to be from seizures, with no clear outcome. He was awake and alert within 24 hours of medical admission but became agitated, hostile, and psychotic prompting psychiatric admission. When his worsening paranoia had resulted in termination of his visiting nurse services that administered injections and in home assessments, his outpatient psychiatrist allowed him to self-administer bi-monthly injections. Over three weeks in the hospital, he was evaluated for signs and symptoms of antipsychotic overdose.

Results

Initial literature review did not reveal information involving an overdose of injectable Risperidone. Thus, the time frame and symptoms to monitor were uncertain. As the injectable medication was expected to peak in 2-3 weeks and persist for 4-6 weeks, there was a concern about delayed potential side effects such as EPS, sedation, QTC prolongation and electrolytes imbalances. He was treated with oral antipsychotic medication. Clozapine and doxepin were discontinued due to patient non-adherence, side effects, and drug interactions. He exhibited signs of EPS and was started on benztropine. To simplify his regimen, he was switched to another long acting injectable, Paliperidone Palmitate, prior to his discharge.

Conclusions

Given the nature of the presentation, he was advised not to self-administer injectable medication and was referred for visiting nurse services. He was educated on the potential side effects of injectable antipsychotic medication. As there was a change in antipsychotic medications, follow up was recommended in an intensive outpatient program for psychotic symptoms and prolonged side effects. Due to the patient’s concordant episode of loss of consciousness, he was advised to follow up with an outpatient long term EEG monitoring and complete Neurology evaluation.

Funding Acknowledgements

No funding.