Effects of Accidental Overdose of Paliperidone Palmitate

Case Reports in Psychiatry
13 Apr, 2019 ,

Case of a 21-year-old male with a history of mental illness that presented with selective mutism, disorganized speech, thought process, behavior, and auditory hallucinations who accidentally received 624 mg Paliperidone Palmitate intramuscularly with no reported side effects after 2 weeks of monitoring and observation. Paliperidone is a D2, 5HT2A receptor antagonist with additional antagonist activity at α-1 and α-2, H-1 receptor sites, and four metabolic pathways identified for its metabolism.

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Patient is a 21-year-old African American male, single, unemployed, and homeless with a reported history of mental illness and no past medical history who was brought in by ambulance from the shelter for psychiatry evaluation as the patient was reportedly found talking to himself. Upon evaluation in the psychiatry emergency room (ER), he was uncooperative and selectively mute. He reported recent relocation to New York from California 2-3 months prior to presentation; however, the exact duration of his symptoms could be not elicited and no valid collateral could be obtained. He reported he was on Olanzapine 10 mg orally daily and needed to get a refill. Patient was grossly disorganized in his speech, thought process, and behavior. He was internally preoccupied; he was seen smiling and mumbling to self. His mentation was slowed and he had difficulty processing information with poor reality testing. Urine toxicology was negative for any illicit substance on admission. He was admitted to the inpatient psychiatry unit for stabilization after receiving a stat dose of Olanzapine 5 mg orally in the psychiatry emergency room. On the inpatient unit, patient was started on the Olanzapine 20 mg orally at bedtime for psychosis, Valproic acid 500 mg orally twice daily for mood stabilization due to agitation and low dose, regular form of Trazodone 100 mg orally at bedtime for sleep on day 1 of his hospital course. Patient was compliant with his medication and after 2 weeks of compliance with Olanzapine, he remained grossly disorganized and internally preoccupied, constantly seen responding to internal stimuli. His medications were reviewed, Olanzapine cross-tapered with Risperidone on day 14 with the aim of giving him Paliperidone Palmitate (Invega Sustenna) if the patient improves on a trial of Risperidone. He was started on Risperidone 1 mg orally twice daily which he tolerated with no report of adverse effect. On day 17, he was given the first dose of Invega Sustenna 234 mg intramuscularly (IM), well tolerated with no report of side effect or adverse drug reaction. He received the second dose of Invega Sustenna 156 mg IM five days after the first dose on day 22, also well tolerated with no report of side effect or adverse drug reaction. On day 28, six days after he received the second dose of Invega Sustenna, patient received another dose of Invega Sustenna 234 mg IM due to name error. Patient was mistaken for another patient who bears the same last name. Patient was immediately evaluated, given Benztropine 2 mg IM stat for extrapyramidal symptom prevention.

The patient was closely observed for extrapyramidal and dose-related side or adverse effects such cardiac arrhythmias, QTc prolongation, dizziness, extrapyramidal symptoms, and hypotension. Patient had stat electrocardiogram (EKG), complete blood count, and complete metabolic profile which were normal. Carbamazepine 400 mg orally stat then 400 mg every 8 hours was commenced the following day with the aim of decreasing serum levels of Paliperidone. Serial daily EKG was ordered for monitoring of QTc, and vital signs were checked every 15 minutes. Patient was also instructed to report any unusual or abnormal feelings which could be related to the high dose of Paliperidone Palmitate or side effects associated with hyperprolactinemia. Serum prolactin level was not done as patient had no report of side effects related to hyperprolactinemia. After 2 weeks of close monitoring, patient did not report any of the reported side effects of Paliperidone Palmitate and none was observed by the treatment team. Patient was discharged on day 55 of admission with no reports or observed side effects associated with Paliperidone Palmitate.