Antiepileptic Drugs 2
Terms
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- Simple Partial Seizure
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focal seizure
consciousness preserved - Complex Partial Seizure
- altered consciousness; bilateral cerebral involvement
- Secondarily Generalized Seizure
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tonic/clonic seizures
partial seizures that orginate in cortical structure -> thalamus and brainstem - Phenytoin
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Mechanism: binds to inactivation particle in Na channel, delays recovery from inactivation
Pharmacokinetics: water insoluble at neutral pH, so i.v. is highly alkaline -> muscle necrosis is extravasates; hepatic metabloism is non-linear, clearance declines as conc. increases
Clinical Use: simple partial, complex partial, and and primary secondary generalized tonic-clonic seizures and primarily generalized tonic clonic seizures
Side Effects: ataxia, nystagmus, lethargy, rash, teratogenic 2-3x risk - Carbamazepine
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Mechanism: same as phytoin
Pharmacokinetics: slowly titrated, orally absorbed
Clinical Use: First line drug for Partial Seizure esp in children, can worsen abscence seizure; CN V and IX neuralgia; bipolar disorder
Side Effects: well tolerated
chronic - leukopenia, aplastic anemia - Lamotrigine
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Mechanism: similar to phenytoin, additional action at K channel (hyperpolarization), oral only
Clinical Use: Broad Spectrum, refractory tonic, atonic and absence; Partial seizures and seizure assoc. Lennox-Gastaut syndrome; bipolar disorder
Side Effects: toxic CNS similar to phenytoin, rash - Topiramate
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Mechanism: blocks glutamate receptor
Clinical Use: broad spectrum anticonvulsant, second line partial seizure and assoc with Lennox-Gastaut
Side Effects: anxuety, memory and conc. difficulty - Levetiracetam
- add-on therapy for partial seizures in refractory patients and those with hepatic dysfunction (renal metabolism)
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Lorazepam
Diazepam
Tiagabine
Gabapentin -
enhance GABA inhibitory potential
Effective for partial seizures
Tigabine NOT to be used in generalized epilepsy
Gabapentin only effective with another anticonvulsant -
Phenobarbital
Primidone - Barbiturates are the cheapest anticonvulsant available; third-line drugs
- Generalized Seizures
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Absence- young children, staring out in space
Myoclonic- 12-20 yo
Tonic- brief stiffening of arms
Atonic- fall over, risk of head injury
Tonic-Clonic - Ethosuximide
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Mechanism: blocks T-type Ca channel, long T1/2 (30-50 hrs)
Clinical Use: Pure Absence seizures
Side Effects: very safe, anxiety or other behavioral - Valproic Acid
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Mechanism: like phenytoin, inhibits Na currents, also smaller effect on T-type Ca channel and increases GABA
Clinical Use: broad specturm against abscence, myoclonic, tonic, and tonic clonc and partial seizures; bipolar and migraine
Side Effects: tremor, sedation fetal malformation, fulminating hepatitis - Felbamate
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Not really used
Clinical Use: refractory tonic, atonic and absence and partial seizures
Side Effects: aplastic anemia, hepatotoxicity -
Clonazepam
Clorazepate
Diazepam
Lorazepam -
Benzodiazepines with broad anticonvulsant properties.
Long term treatment: Clonazepam and Clorazepate
Status Epilectus: Lorazepam (superior) and Diazepam -> follow with fosphenytoin or if ineffective use pentobarbital or propofol