Antiepileptics 1/18 Flashcards
classic AEDs
phenytoin,carbamazepine, phenobarbital,benzodiazepines,valproate,ethosuximide
newer AEDs
oxcarbazepine,gabapentin,lamotrigine,felbamate,
tiagabine,levetiracetam,zonisamide,topiramate
phenytoin
inhibits Na channels, use-dependent.first line for partial,grand mal,status epilepticus.
prodrug is fosphenytoin for IM,IV.highly bound to plasma proteins.zero order kinetics.
adverse effects:CNS sedation,gum hyperplasia,hirsu,teratogenic
interactions of phenytoin with other drugs
carbamazepine,phenobarbital will decrease plasma levels.
EtOH,diazepam,methylphenidate will increase.
valproate can displace from plasma proteins.
stimulates cytochrome P-450–>increase metabolism of others
therapeutic range is narrow
carbamazepine
inhibits Na channels, use dependent. most widely used.derived from TCA.
first line for partial and grand mal.
adverse effects:CNS sedation,diplopia,ataxia,agranulocytosis,aplastic anemia in elderly (rare), increases ADH, teratogenic.
stimulated metabolism of other drugs and its own.
phenobarbital
allosteric modulator of GABAA,increase open time.partial seizure.effective in neonates.
adverse effects: sedation,tolerance and physical dependence. severe CNS depression when combined with EtOH and benzos.stiumulates cytochrome P450.
overdose–>coma and resp depression
seldom used
Benzodiazepines
allosteric modulator of GABAA receptors. increase open frequency.
status epilepticus.rapid onset. valium available for rectal.
CNS sedation,tolerance and dependence.can inhance action of other CNS depressants
Valproate
inhibits low threshold T-type Ca channels,enhances GABA transmission,blocks Na channels
simple monocarboxylic acid unrelated to any antiepileptic.
partial, first line for generalized, grand mal,myoclonic..
adverse effects:CNS depressant,n/v,hair loss,weight gain,hepatoxicity,may cause birth defects.
displaces phenytoin from plasma proteins,P450 inhibitor
Ethosuximide
inhibits T-type Ca current in thalamus.
absence seizure.
adverse effects:gastric distress,less CNS effects,transient fatigue,dizziness,hematotoxicity.
administration with valproate results in inhibition of its metabolism
oxcarbazepine
blocks Na channels,use dependent.
add-on therapy for partial that are refractory to other AEDs.
similar adverse effects to carbamazepine but less toxic.less induction of liver enzymes but can stimulate CYP3A and inhibit CYP2C19
gabapentin
inhibits voltage sensitive L-type Ca channels (a2D2 subunit) and may interfere with GABA uptake.
add-on for partial, evidence that it’s also effective as monotherapy in newly diagnosed partial.
eliminated renally.less CNS effects.no drug interactions
lamotrigine
inhibits Na channels,use-dependent.
add-on for partial,effective against generalized.
less CNS sedation,dermatitis,Steven-Johnson syndrome.
levels increased by valproate.decreased by carbamazepine,phenobarbital,phenytoin
felbamate
modulation of NMDA and GABA receptors.
third-line for partial.
aplastic anemia and severe hepatitis.
increases plasma phenytoin+valproate.decreases carbamazepine.Stimulates CYP3A and inhibits CYP2C19
tiagabine
inhibits reuptake of GABA.Analog of GABA(penetrates BBB).
short 1/2 life.
add-on for partial.CNS sedations and confusion.
minimal drug interactions.
levetiracetam
binds to synaptic vesicle protein SV2,may regulate NT release.
developed as an analogue of piracetam, used for congnitive function as a memory enhancer.
add-on for partial.
CNS depression.behavioral mood swings.
minimal drug interactions.
Common adverse effects
