Antiepileptic Drugs Flashcards
Na channel blockers
Phenytoin (Oxcarbazepine-children)
Fosphenytoin (prodrug)
3 ways antiepileptic drugs work
Prevent abnormal changes in ion conductance : block Na,K, Ca channels
Decrease excitatory activity: block NMDA and AMPA receptors
Increase inhibitory transmission: increase GABA synthesis or release
Phenytoin
Blocks Na channels by binding to inactive gate delaying onset of neuron firing
Extravasation causes tissue injury
Hypotension
*
Phenytoin drug interaction
Increases conversion of primidone to phenobarbital
Enhances carbamazepine by inducing CYP3A4
Phenytoin side effects
dont use with juvenile myoclonic seizure
*gingival hyperplasia and hirsutism
Felbamate
Glutamatergic (excitatory) receptor antagonist
Use only in:
Lennox-Gastaut Syndrome
Pts highly refractory to other drugs
Inhibits NMDA channel
Binds to NR2B and NR1 subunits, delaying recovery of desensitized NMDA channels
What can Felbamate cause?
Liver failure
Gabapentin
Releases GABA from glial cells
Used for neuropathic pain and seizures, NOT for controlling seizures
GABA agonists
Agonizing GABA increases Cl- influx = hyperpolarization
Gabapentin
Tiagabine
Vigabatrin
Tiagabine
Inhibits reuptake of GABA by GABA transporter
Controls tonic-clonic seizures for children under 12
Vigabatrin
Inhibits metabolism of GABA by GABA transaminase
Tx of infantile spasm and refractory complex partial seizures
Myoclonic seizures
Juvenile
Single/multiple jerks in face, neck, and upper
Most originate from brainstem in the CNS
Valproic acid
Tx for juvenile myoclonic seizures
Block Na+ channel
Adverse effects of Valproic acid
If used during pregnancy causes Spina bifida
If pregnant, give VPA with folate
Zonisamide
Na and Ca antagonist
Myoclonic seizures
*causes renal stones
Lamotrigine
Na channel blocker
Myoclonic seizures with mild side effects
Absence seizure (petit mal)
Brief and abrupt unconsciousness (5-10sec)
Onset 4-12 and continues to adolescence
High voltage bilaterally synchronous spike wave discharge
Ethosuximide
Used to tx absence seizure (petit mal)
Blocks T-type Ca+ channels
Binding reduces Ca entry and suppresses spike wave activity
Valproate
Tx absence seizures (petit mal) with tonic-clonic attacks
Lamotrigine
Na channel blocker used in children with absence seizures
Status epilepticus
Seizure activity the lasts 10min without recovery, or two or more seizures within 30min
Mostly in ppl >30
Lorazepam
Benzodiazepine GABA agonist Low lipid solubility Lasts 6-12hrs Less respiratory depression
Diazepam
Benzodiazepine
GABA agonist
High lipid solubility -accumulates, toxicity
Rapid onset
Respiratory depression and hypotension
Partial and generalized seizures tx
Phenytoin, Oxcarbazepine (child)
