Prolonged Stupor in Perampanel Overdose and Pharmacokinetic Considerations

A Case of Perampanel Overdose Presenting with Respiratory Failure

Perampanel is a novel antiepileptic drug that has been used as an adjunctive treatment for focal-onset seizures. No reports to date have documented respiratory suppression as a side effect of perampanel in adults. Herein, we report a 51-year-old man with focal epilepsy presented with type 2 respiratory failure after accidently consuming of 66 mg of perampanel. Clinicians should consider the possibility of respiratory compromise whenever a high dose of perampanel needs to be administered to patients.

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.

"Zombielike" Aggression in Perampanel Overdose

Perampanel is an antiepileptic drug that blocks amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors. To date, little is known about the management of perampanel intoxication. We report a case of “zombielike” behavior secondary to intentional perampanel overdose. An 18-year-old male with idiopathic generalized epilepsy and focal features presented with aggressive and “zombielike” behavior after suicide attempt via intentional perampanel overdose, amounting to approximately 128 mg. Clinical symptoms gradually improved with continuous dexmedetomidine infusion and intravenous lorazepam boluses five days after being admitted to the intensive care unit. While perampanel intoxication has been reported to be associated with central nervous system-related adverse effects, awareness of this association is necessary to prompt more appropriate management tailored to perampanel toxicity.

Perampanel overdose in low body mass index patients with epilepsy: a case report and review of the literature

Background

Perampanel (PER) is a novel antiepileptic drug (AED) which employs a completely different mechanism of action compared to existing medications. Overall, PER is considered to be safe up to a dose of 12 mg per day. When used to treat refractory and super-refractory status epilepticus, PER seems to be extremely well tolerated; this is true even when used at doses of up to 32 mg. There are currently only three case reports on the effects of acute PER overdose in epilepsy patients.

Case presentation

We report a 16-year-old Thai woman with a low body weight, who took PER at a dose of 40 times that of the prescribed daily dose. She experienced only an alteration of consciousness, without any systemic medical effects, and made a full recovery within 3 days without gastric lavage or specific treatment.

Conclusion

Our report demonstrates that an acute PER overdose may not produce serious adverse systemic effects. Individuals with adverse central nervous system (CNS) effects, such as altered consciousness, can experience a rapid recovery.

Development and application of an HPLC-DAD technique for human plasma concentration monitoring of perampanel and lamotrigine in drug-resistant epileptic patients

Perampanel is a third-generation antiepileptic drug (AED), while lamotrigine is a second-generation AED. Both drugs are subject to extensive pharmacokinetic variability between different patients. Furthermore, it has been reported that perampanel and lamotrigine may be implied in pharmacokinetic drug-drug interactions with other AEDs such as carbamazepine or valproate, with consequent alterations of plasma concentrations. This emphasizes the relevance of therapeutic drug monitoring of perampanel and lamotrigine with appropriate bioanalytical methods. Herein, the development and validation of a bioanalytical techique for the simultaneous quantification of perampanel and lamotrigine in human plasma samples is described. The reported method is based on high-performance liquid chromatography coupled with diode-array detection (HPLC-DAD) and sample preparation consists of liquid-liquid extraction. Chromatographic separation of the analytes (lamotrigine and perampanel) and the internal standard (entacapone) was achieved in 12 min on a reversed-phase C₁₈ column at 40 °C by applying a gradient elution program with a mobile phase composed of 0.1% ortho-phosphoric acid pH 2.79 (A) and acetonitrile (B) pumped at 1.0 mL/min. Perampanel was quantified at 320 nm while lamotrigine and the internal standard were monitored at 306 nm. Calibration curves were linear in the concentration range of 0.03-4.5 µg/mL (r² = 0.9978) for perampanel and in the concentration range of 0.25-30 µg/mL (r² = 0.9981) for lamotrigine. Overall precision did not exceed 14.3% and accuracy ranged from -6.08 to 12.66%. Some drugs potentially co-prescribed with perampanel and lamotrigine were tested and did not interfere with the retention times of the analytes and internal standard. The method was then successfully applied for the quantification of perampanel and lamotrigine in plasma samples obtained from 42 drug-resistant epileptic patients admitted to the Coimbra University Hospital Centre (CHUC.EPE, Coimbra, Portugal). In conclusion, it is a suitable method for the therapeutic drug monitoring of lamotrigine and perampanel in drug-resistant epileptic patients, as well as, for the assessment of drug-drug interactions. It can also be adopted by hospitals and laboratories, when HPLC with fluorescence and mass spectrometry detections are unavailable.

Prolonged unconsciousness in perampanel overdose

Clinical experience of perampanel overdoses is markedly limited and the relevant literature is sparse. Perampanel is a novel antiepileptic drug (an amino-3-hydroxy-5-methyl-4-isoxazlepropionic acid glutamate receptor antagonist) with a long half-life, which is used for the adjunctive treatment of epilepsy. The literature available identifies a potential for prolonged unconsciousness in overdose. We report a case of prolonged unconsciousness for 14 days following a perampanel overdose of 3.5 times the maximum daily dose, requiring protracted intubation and ventilation on intensive care, with eventual complete neurological recovery. This represents the longest known period of unconsciousness with full recovery and the first reported in a perampanel naïve patient. This case helps to inform decision-making in critical care, particularly the early consideration of admission and intubation. It highlights that while perampanel overdose may not initially cause systemic effects such as cardiac toxicity, it can cause protracted altered consciousness with secondary compromise requiring prolonged intensive care management.