Anticonvulsants

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  1. phenytoin and fosphenytoin
    • blocks Voltage gated Na+ channels (and VG Ca2+ channels)
    • drug of choice for initial therapy of epilepsy (oral)
    • - partial simple, partial complex, tonic-clonic seizures, emergency rx of status epilepticus (IV)
    • NOT used for absence seizures
    • liver metabolized - can cause saturation at high dosage, enhances P450
    • phenytoin metabolism stimulated by carbamazepine
    • phosphenytoin is prodrug, can be given IM
    • adverse effect: gingival hyperplasia, megaloblastic anemia, teratogenic
  2. carbamazepine
    • blocks Voltage gated Na+ channels
    • drug of choice for partial simple, partial complex, and tonic-clonic seizures
    • other use: trigeminal neuralgia, bipolar disorder
    • admin: oral, slow absorbed, highly lipid soluble
    • metabolized by hepatic P450 enzymes, induces P450 enzymes which increases its own metabolism during chronic administration
    • adverse effect: hepatotoxicity, teratogenic
  3. valproic acid
    • blocks VG sodium and calcium channels
    • facilitates GABAergic synaptic transmission
    • drug of choice for myoclonic seizures
    • second line (due to hepatotoxicity) for TC and absence seizures
    • oral - rapidly absorbed, high level of plasma protein binding
    • metabolized by liver P450
    • Divalproex is combination sodium valproate and valproic acid (improve GI tolerance)
    • adverse effect: hepatotoxicity, thrombocytopenia, teratogenic
  4. ethosuximide
    • blocks VG T-type calcium channels in thalamic neurons (suppressed rhythmic activity)
    • drug of choice in absence seizures
    • oral - well absorbed, NOT bound to plasma proteins
    • long half life
    • 75% metabolized by hepatic enzymes, 25% excreted unchanged
  5. phenobarbital and primidone
    • barbiturates - facilitates activation of GABA receptors to increase inhibitory tone
    • treat simple partial and recurrent TC seizures, as well as febrile seizures in children
    • combined with carbamazepine and phenytoin to allow for smaller doses
    • other use: rx anxiety
    • oral: well absorbed, freely penetrates brain
    • 75% inactivated by hepatic microsomal system
    • metabolite of primidone is phenobarbital
    • adverse effect: megaloblastic anemia, teratogenic
  6. diazepam and lorazepam
    • benzodiazepine - potentiate activation of GABA receptors
    • drug of choice for acute status-elipticus, (clonazepam) treats myoclonic and absence seizures
    • other use: anxiety drug of choice
    • tolerance can develop after 1-6 mo
  7. lamotrigine
    • blocks voltage gated sodium channels, also inhibits glutamate release
    • used to treat simple partial, complex partial, and generalized TC seizures
    • metabolized by liver
    • drug interactions: half life decreased by enzyme-inducing drugs (carbamazepine, phenytoin) and increased by valproic acid
  8. gabapentin
    • blocks calcium channels (binding to α2-δ subunit) and release of glutamate, enhances GABAergic synaptic transmission
    • used in simple or complex partial seizures and generalized TC
    • not metabolized, doesn't induce hepatic enzymes
    • not bound to plasma proteins
    • short half life
    • eliminated by kidneys
    • negligible drug interactions
  9. pregabalin
    • blocks calcium channels (binding to α2-δ subunit) and release of glutamate
    • used in simple or complex partial seizures
    • adverse effect: thrombocytopenia
  10. topiramate
    • blocks sodium channels, increase activity of postsynaptic GABAa receptors
    • used in simple or complex partial seizures and generalized TC
  11. levetiracetam
    • modifies glutamate and GABA release via binding to synaptic protein SV2A
    • broad spectrum for partial and generalized seizures (TC, MC)

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Author:
jboi
ID:
323813
Filename:
Anticonvulsants
Updated:
2016-09-28 18:41:50
Tags:
mohd4 pharmacology anticonvulsants
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Description:
MOHD4 lecture 63
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