(990) Neuroleptic Malignant Syndrome From Suspected Amantadine Withdrawal in a Hospitalized Child

Introduction: Intentional discontinuation of some home medications due to a change in health during hospitalization may result in withdrawal symptoms of varying severity. Withdrawal from amantadine is lesser known in pediatric patients. Amantadine increases synaptic dopamine availability and is used in treatment of Parkinson’s disease and in pediatric behavioral conditions alike. Amantadine withdrawal has been reported in adult Parkinsonism to cause neuroleptic malignant syndrome (NMS) which occurs in the setting of sudden dopamine deficiency. Herein we report a case of a child who developed NMS from suspected amantadine withdrawal.

Description: A 16-year-old male with a history of autism spectrum disorder and epilepsy was hospitalized for increasing seizure frequency. Brain CT and lumbar puncture were normal, and he was given loading doses of lorazepam and levetiracetam for clinical seizures. Once admitted, he was placed on continuous video-electroencephalogram (EEG). Home medications of amantadine (100mg taken twice daily for agitation), doxepin, clonidine, tizanidine, and lisdexamfetamine were held on admission in the setting of suspected iatrogenic somnolence and a post-ictal state. Approximately 24-36 hours from his last amantadine dose, he developed fever (40.1 C), irritability, tachycardia (165 beats per minute), muscle rigidity, hyperreflexia, and abnormal flexion and extension of his extremities without an EEG seizure correlate. Electrolytes were unremarkable and total creatinine kinase (CK) was 128,067 U/L, raising suspicion for NMS. Dexmedetomidine was initiated in place of clonidine without improvement. Amantadine was restarted upon which NMS symptoms began to improve within approximately 6 hours. The patient returned to baseline and was discharged home three days later.

Discussion: Given the severe nature of NMS, prompt identification of the cause is an essential component of patient management, and children with developmental delay are at risk for delayed recognition of various conditions. In pediatrics, NMS may be commonly attributed to side effects of dopamine antagonists. This case highlights the potential for NMS from amantadine withdrawal in a pediatric patient without an underlying Parkinsonism-like condition.