Clinical management of medication overdose: Three-monthly paliperidone palimitate injectable medication

To the Editor

A 46-year-old Aboriginal female diagnosed with schizophrenia (multiple episodes, currently in full remission) living in a remote Northern Territory community inadvertently received two doses of 350 mg three-monthly injectable paliperidone palmitate (Trinza) on 31 December 2020 and on 5 January 2021.

At the time of the prescribing error resulting in the ‘double-dosing’, the consumer was experiencing an acute kidney injury secondary to bacteraemia with a serum creatinine of 166 µmol/L. Given her co-morbid poorly controlled type 2 diabetes mellitus (T2DM) and cannabis use disorder, a decision was made in conjunction with the consumer, her family and the General Medicine team to transfer to a tertiary setting for further treatment and management.

Consequently, her admission provided an opportunity to formulate a clear observation process to her medication overdose and monitor for any immediate complications. Throughout her admission course from 13 January 2021 to 22 January 2021, she was monitored closely for cardiac (hypotension, tachycardia, QTc prolongation) and neurological (Neuroleptic Malignant Syndrome, acute dystonia and akathisia) sequelae of overdose. Although she experienced initial hypotension (low of BP 89/43), no further complications were observed. Her mental state was closely observed, and there was no acute confusional state or withdrawing complication from her cannabis use disorder. With a resolving acute kidney injury upon discharge with a serum creatinine of 90, no further renal management was required.

General Medicine, Psychiatry and the General Practitioner managing her care formulated an ongoing community management plan to asses for any ongoing complications at the times of expected peak plasma levels of medication. Two-weekly ECGs to monitor QTc and twice weekly psychiatric review to assess for extrapyramidal side effects and monitor her mental state was initiated. To guide ongoing management, monthly plasma 9-hydroxy risperidone levels were collected. These were recorded at 67.6 ng/mL on 27 January 2021, 48.3 ng/mL on 2 February 2021 and 42.9 ng/mL on 17 March 2021 (therapeutic range, 20–60 ng/mL).

Fortunately, the consumer’s physical health, mental state and ECGs remained stable post-discharge, and there was no requirement for escalating management to a tertiary setting. There has been no clinical complications post ‘double dose’ and the consumer’s mental state has remained stable. She has recommenced her regular dose of three-monthly paliperidone palmitate (given on 21 April 2021).

The literature is scant regarding long-acting injectable antipsychotic medication overdose and its clinical management. Although there has been a report in the literature (Ojimba et al., 2019) of a patient inadvertently receiving multiple one-monthly paliperidone (Sustenna) in close sequence, this may be the first reported case of an inadvertent multiple three-monthly injection, fortunately with no adverse outcomes.