Pediatric perampanel poisoning

Severe Perampanel Toxicity in a Pediatric Patient With Prolonged Symptoms

BACKGROUND

Perampanel is a new antiepileptic used to treat partial-onset seizures and generalized tonic-clonic seizures in people older than 12 years old. Perampanel is a selective, non-competitive α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist, with a prolonged half-life of approximately 105 hours. Few cases of significant toxicity have been reported, and effects in overdose are poorly understood.

CASE REPORT

This case describes a 20-month-old healthy female who ingested 8 mg of perampanel. She presented to a pediatric emergency department 1 hour after ingestion with ataxia, irritability, and somnolence. Vital signs were: heart rate 130 beats per minute, blood pressure 112/97 mmHg, temperature 99°F, respiratory rate 30 breaths per minute. She was admitted to the pediatric intensive care unit. During the hospitalization, she developed hypotension and bradycardia which improved with stimulation and fluid resuscitation. Intermittent bradycardia persisted for 32 hours after ingestion. Physical examination was notable for somnolence and truncal ataxia with irritability when aroused, all of which improved throughout the hospitalization. A quantitative level obtained on hospital day 3 (HD) was 750ng/ml. On HD 3 the patient was noted to be ataxic but otherwise had an age-appropriate neurologic examination. She was discharged on HD 4 with normal vital signs, return to baseline mental status, and baseline gait. The patient's cardiovascular, neurologic, and behavioral symptoms were attributed to perampanel toxicity. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS ?: Toxicity from a perampanel overdose is poorly understood both in adults and pediatric patients with significant cardiovascular, behavioral, and central nervous system abnormalities.

Clinical effects and outcomes of perampanel overdoses reported to U.S. poison centers

INTRODUCTION

Perampanel is indicated for partial onset seizures in children and adults. The mechanism is unique among antiepileptic agents as it inhibits glutamate activity on AMPA receptors. Currently, there are few published case reports describing overdose.

METHODS

This is a retrospective observational study of all single substance perampanel ingestions from January 2014 to December 2019 reported to the national poison data system (NPDS). The primary outcome is to describe the clinical effects of perampanel exposures. Secondary outcomes include evaluation of management and investigation of a dose-effect relationship for the purpose of triaging acute unintentional exposures.

RESULTS

A total of 138 exposures were reported to NPDS since the release of the agent. Median age was 20 years (IQR 10-38) with 68 (49.3%) males. The reason for exposure was most commonly therapeutic error (80, 58.0%), followed by exploratory ingestion (24, 17.4%), and suicidal ingestion (14, 10.1%). A total of six (4.3%) patients developed major effects, 20 (14.5%) moderate, 32 (23.2%) minor effects and 22 (15.9%) no effect. An additional 54 (39.1%) cases were not followed. Almost half of cases were managed at home. Of those that were in a healthcare facility (HCF) (n = 72), most were treated/evaluated and released (31, 43.1%), followed by admission to a non-critical care unit (20, 27.8%), and critical care unit (13, 18.1%). Most frequently reported symptoms were drowsiness (27, 19.6%), agitation (20, 14.5%), ataxia (13, 9.4%), and confusion (12, 8.7%). The most common therapies provided in a HCF were intravenous fluids (22,30.6%), followed by benzodiazepines (14, 19.4%), then other types of sedation (9, 12.5%). There were too few cases to determine a dose cut off for triaging.

CONCLUSIONS

While drowsiness, agitation, ataxia, and confusion were the most often reported symptoms, close to 19% developed moderate/major effects and almost 4% of patients received potentially life-saving interventions.

Truncal Ataxia and Prolonged Coma in an Exploratory Pediatric Perampanel Ingestion

INTRODUCTION

Several overdoses of the antiepileptic drug perampanel have been reported in adults, but very few have been reported in children. We report the case of an observed exploratory ingestion of perampanel in a 2-year-old child that resulted in ataxia and prolonged coma.

CASE REPORT

A previously healthy 2-year-old female patient presented to the emergency department (ED) 30 minutes after the witnessed ingestion of 30 mg of perampanel (2 mg/kg). Within minutes of ingestion, she displayed ataxia and inability to walk. Upon ED presentation, she had normal vital signs but was minimally responsive with physical stimulation. Naloxone was given without response. She was intubated because of profound central nervous system depression and transferred to a pediatric tertiary care facility. She remained intubated with no pharmacological sedation. Physical exam showed a horizontal nystagmus. Detailed neurologic examination of ataxia and coordination was not possible, and she did not demonstrate hyperreflexia, clonus, or rigidity. Her mental status gradually improved, and she was extubated approximately 72 hours after exposure. After extubation, the patient still exhibited truncal ataxia and did not return to baseline until 96 hours post ingestion. Serum drawn approximately 16 hours after exposure showed 870 ng/mL perampanel (ref < 20 ng/mL). She remained hemodynamically stable throughout her hospital course, despite protracted depressed mental status.

DISCUSSION

Given the severity of our patient's presentation, pediatric patients showing symptoms of perampanel overdose should be triaged to the ED for evaluation in anticipation of a prolonged clinical course with decreased consciousness and hypoventilation.