Psychosis, Catatonia and Tachypnoea Following Paliperidone Palmitate 3-Monthly Injection Error: Case Report.

Introduction: Paliperidone palmitate 3-monthly (PP3M) is a long-acting Injection (LAI) formulation of the anti-psychotic medication paliperidone, also known as 9-hydroxyrisperidone (9-OH-RIS). There is a notable absence of clinical guidelines or case reports pertaining to PP3M overdose and management of incorrect dosing. Patient Concerns and Clinical Findings: We present the first reported case of PP3M administered at 1 monthly intervals for three consecutive months in the community setting and describe the inpatient management of psychosis and catatonia occurring in the context of this overdose. Diagnoses Interventions and Outcomes: During this patient's admission to an inpatient psychiatric unit, our team, involving specialised pharmacy, navigated the acute management of psychosis in the context of PP3M overdose in the absence of published guidelines. We share the use of electroconvulsive therapy (ECT) and oral lorazepam in managing this patient's acute psychosis and catatonia presentation and provide a rationale for the timing of safe recommencement of paliperidone oral medication. The patient was safely discharged home. Conclusions: We highlight the need for LAI overdose guidelines as an important area for review and development of clinical guidelines as we see increasing use of paliperidone palmitate 1-monthly (PP1M), PP3M, and paliperidone palmitate 6-monthly injection (PP6M) in the community.