newer anticonvulsants: targets and toxicity...antiepileptic drugs for improved tolerability and...
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Newer Anticonvulsants: Targets and Toxicity
Laura Tormoehlen, MDNeurology and EM-Toxicology
Disclosures• No financial disclosures
DEFINITIONS
Objectives/Outline• Mechanism of Action• Specific Indications• Toxicity• Adverse Effects
LACOSAMIDE
Lacosamide• Trade Names: Vimpat• Dosage Forms: Oral, Intravenous• Mechanism of Action: Functionalized Amino Acid, decreases
hyperexcitability via:– Enhancing slow inactivation of voltage-gated sodium channels– CRMP-2 binding
• Indication:– Partial seizure, monotherapy– Partial seizure, adjunct
Lacosamide : Targets
Beyreuther BK, et al. Lacosamide: A Review of Preclinical Properties. CNS Drug Reviews 2001: 13(1): 21-42
Lacosamide : Toxicity• Cardiac Arrest
– 1 Fatal (Malissin 2013, PMID 23534387)
• Ingestion of 7 grams of lacosamide• Co-ingestion with lamotrigine, phenobarbital, and carbamazepine, plus• Initial rhythm asystole, resuscitated, followed by shock and multi-organ failure
– 1 Survival (Chua-Tuan 2015, PMID 25951877)
• Ingestion of 4.5 grams of lacosamide• Co-ingestion of cyclobenzaprine and levetiracetam• Initial rhythm pulseless ventricular tachycardia
• Coma and Seizures (Bauer 2008, PMID 20171144)
– Ingestion of 12 grams of lacosamide– Co-ingestion with gabapentin (56g), topiramate (2g), zonisamide (2.8g)– Also had PR prolongation (265 ms) and hypotension (60/30 mmHg)
Lacosamide : Adverse Effects• Common: Nausea/Vomiting, Somnolence, Memory
Impairment, Dizziness/Vertigo, Headache, Diplopia, Ataxia, Tremor
• Worse with other VGSC blocking agents• Serious
• CV – Atrial fibrillation/flutter, PR interval prolongation, all degrees of AV block, bradycardia, syncope
• Immune – Drug hypersensitivity• Psych – Suicidal thoughts/behavior, Depression, Hallucinations
LACOSAMIDEAnother Parenteral Sodium Channel Blocker
RUFINAMIDE
Rufinamide• Trade Names: Banzel• Dosage Forms: Oral• Mechanism of Action: Triazole Derivative
– Prolongs inactive state of sodium channels
• Indication:– Lennox-Gastaut syndrome, seizure, adjunct– Off Label: Partial seizure, adjunct
Rufinamide : Targets
Johannessen-Landmark C and Johannessen SI. Pharmacological Management of Epilepsy. Drugs 2008; 68(14): 1925-39.
Rufinamide : Toxicity• An adult received 7200 mg during a clinical
trial without any adverse effects
Rufinamide : Adverse Effects• Common: Nausea/Vomiting, Somnolence, Dizziness,
Headache, Diplopia/Blurred Vision, Ataxia/Gait Disturbance, Shortened QT Interval
• Serious:– Neurologic – Status Epilepticus– Psychiatric – Suicidal behavior– Hematologic – Leukopenia– Immune – Drug hypersensitivity syndrome/DRESS, Stevens-Johnson
syndrome
RUFINAMIDEYet Another Sodium Channel Blocker, for Lennox-Gastaut
ESLICARBAZEPINE
Eslicarbazepine• Trade Names: Aptiom• Dosage Forms: Oral• Mechanism of Action: Structurally related to
carbamazepine and oxcarbazepine– Inhibition of voltage-gated sodium channels
• Indication:– Partial seizure, monotherapy– Partial seizure, adjuct
Johannessen-Landmark C and Johannessen SI. Modifications of Antiepileptic Drugs for Improved Tolerability and Efficacy. Perspect Med Chem 2008; 2: 21-39
Eslicarbazepine : Targets
Johannessen-Landmark C and Johannessen SI. Pharmacological Management of Epilepsy. Drugs 2008; 68(14): 1925-39.
Eslicarbazepine : Toxicity• Oxcarbazepine
Eslicarbazepine : Adverse Effects• Common: Nausea/Vomiting, Somnolence, Dizziness,
Headache, Diplopia/Blurred Vision, Ataxia, Tremor• Serious:
– Psychiatric – Suicidal thoughts– Ophthalmologic – Visual impairment– Metabolic – Hyponatremia– Hematologic – Eosinophilia– Hepatic – Increased transaminases, Increased bilirubin– Immune – Anaphylaxis, Drug hypersensitivity syndrome/DRESS,
Stevens-Johnson syndrome– Other – Angioedema
ESLICARBAZEPINEA Once-A-Day Oxcarbazepine
PERAMPANEL
Perampanel• Trade Names: Fycompa• Dosage Forms: Oral• Mechanism of Action: Noncompetetive antagonism
of AMPA receptors• Indication:
– Partial seizure, adjunct– Tonic-clonic seizure, adjunct– Orphan drug status for Lennox-Gastaut
Perampanel : Targets
Johannessen-Landmark C and Johannessen SI. Pharmacological Management of Epilepsy. Drugs 2008; 68(14): 1925-39.
Perampanel : Toxicity– Case report: 34 year-old with tuberous
sclerosis (Hoppner 2013, PMID 24001596)
• Ingestion of 204 mg, initially estimated to be 264 mg
• Dysarthria and fatigue, followed by stupor, then misperception and disorientation
• Impaired consciousness lasted 2 days• EEG without epileptiform discharges
Perampanel : Adverse Effects• Common: Somnolence, Dizziness, Headache,
Ataxia/Abnormal Gait/Falls, Dysarthria, Irritability, Mood Disorder
• Serious: – Psychiatric – Aggressive behavior, Homicidal
thoughts, Suicidal thoughts– Dermatologic – Drug hypersensitivity syndrome
PERAMPANELAMPA antagonist, limited use due to SI/HI
CLOBAZAM
Clobazam• Trade Names: Onfi• Dosage Forms: Oral• Mechanism of Action: Benzodiazepine
– Binds to benzodiazepine site of GABA(A) and potentiate neurotransmission
• Indication:– Lennox-Gastaut, seizure, adjunct– Off Label: SGE, Partial seizure, adjunct– Not labeled for EtOH withdrawal or anxiety
Clobazam : Targets
Johannessen-Landmark C and Johannessen SI. Pharmacological Management of Epilepsy. Drugs 2008; 68(14): 1925-39.
Clobazam : Toxicity• It’s a Benzodiazepine
Clobazam : Adverse Effects• Common: Somnolence/Sedation, Ataxia,
Dysarthria, Cough, Fever, Dependence, Constipation, Drooling, Insomnia
• Serious:– Dermatologic – Stevens-Johnson Syndrome, Toxic
Epidermal Necrolysis– Psychiatric – Suicidal Behavior/Ideation,
Aggressive Behavior
CLOBAZAM“Less Sedating” Benzodiazepine
VIGABATRIN
Vigabatrin• Trade names: Sabril• Dosage Forms: Oral• Mechanism of Action:
– Irreversibly inhibits GABA Transaminase– May also stimulate GABA release
• Indication:– Partial seizure, adjunct– Infantile spasms– Restricted distribution, black box warning for vision loss
Vigabatrin : Targets
Johannessen-Landmark C and Johannessen SI. Pharmacological Management of Epilepsy. Drugs 2008; 68(14): 1925-39.
Vigabatrin : Toxicity• Case reports
– Adult ingested 8-12 grams• Psychosis
– 25 year-old woman ingested 60 grams• Severe delirium
Davie MB, Cook MJ, Ng C. Vigabatrin Overdose. Med J Aust 1996; 165: 403.
Vigabatrin : Adverse Effects• Common: Somnolence, Dizziness/Vertigo,
Headache, Agitation• Serious:
– Ophthalmologic: Permanent vision loss– Neurologic: Coma, Seizures– Psychologic: Psychosis– Respiratory: Respiratory depression– Cardiovascular: Hypotension, Bradycardia
VIGABATRINNovel agent, VERY limited use due to visual impairment
EZOGABINE/RETIGABINE
Ezogabine• Trade names: Potiga (US), Trobalt (Europe)• Dosage Forms: Oral• Mechanism of Action: Opens voltage-gated potassium
channels (KCNQ2/3) resulting in hyperpolarization• Indication:
– Partial seizure, in patients with inadequate response to several alternatives, adjunct
– Benign familial neonatal convulsions (loss of function of KCNQ2/3)– Black box warning for retinopathy
Ezogabine : Targets
Johannessen-Landmark C and Johannessen SI. Pharmacological Management of Epilepsy. Drugs 2008; 68(14): 1925-39.
Ezogabine : Toxicity– Moderate: agitation, aggressive behavior,
irritability (doses greater than 2500 mg)– Severe:
• Cardiac dysrhythmias (asystole or ventricular tachycardia) within 3 hours of single 900-mg dose in 2 volunteers.
• QT prolongation known, TdP possible but not yet reported
Product Information: Potiga ® oral tablets, ezogabine oral tablets. GlaxoSmithKline (per FDA), Research Triangle Park, NC, 2015
Ezogabine : Adverse Effects• Common: Fatigue, Memory Impairment, Vertigo,
Diplopia/Blurred Vision, Tremor, Incoordination/Abnormal gait, Aphasia/Dysarthria
• Serious:– Neurologic – Dizziness, Somnolence, Confusion– Ophthalmologic – Retinal disorder, Pigment change– Psychiatric – Hallucinations/Psychosis, Suicidal thoughts– Cardiovascular – Prolonged QT interval– Renal – Urinary retention– Dermatologic – Skin pigmentation (blue, grey, brown)
Zaugg BE, et al. Ezogabine maculopathy. Retinal Cases & Brief Reports 2016; 0: 1-6.
EZOGABINE“Niche drug,” limited use due to retinal/skin pigment changes and urinary retention
GANAXOLONE
Johannessen-Landmark C and Johannessen SI. Modifications of Antiepileptic Drugs for Improved Tolerability and Efficacy. Perspect Med Chem 2008; 2: 21-39
Ganaxolone : Targets
Johannessen-Landmark C and Johannessen SI. Pharmacological Management of Epilepsy. Drugs 2008; 68(14): 1925-39.
SIRIPENTOL
Stiripentol : Targets
Johannessen-Landmark C and Johannessen SI. Pharmacological Management of Epilepsy. Drugs 2008; 68(14): 1925-39.
BRIVARACETAM
Brivaracetam : Targets
Johannessen-Landmark C and Johannessen SI. Pharmacological Management of Epilepsy. Drugs 2008; 68(14): 1925-39.
QUESTIONS?
emedicine.Medscape.com
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