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Flashcards in Anticonvulsants Deck (70):
1

Epilepsy

spontaneous episodes associated w/ loss or disturbances of consciousness, usually but not always accompanied by characteristic body movements and always excessive EEG discharge

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Seizure

transient alteration of behavior due to disordered, synchronous and rhythmic firing of a population of brain neurons

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Focal or partial seizure

60% of epilepsies, originates in one hemisphere of brain, usually due to lesion: head trauma, tumor, stroke, hypoxia at birth, metabolic disorders, malformations, can progress to generalized seizures

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Generalized seizures

originates from both hemispheres simultaneously, loss of consciousness

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Status epilepticus

failure of seizure termination>5 mins

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Tonic-clonic

loss of consciousness w/ tonic stiffening followed by clonic muscle activity

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isolated tonic

mostly in children, increased tone in extensors

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isolated clonic

mostly in small children and babies

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Atonic

abrupt loss of all muscle tone; patients fall

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Absence

hardest to treat, commonly seen in children, brief loss of awareness and behavioral arrest, inhibition of GABA receptors, activation of T-type Ca current leading to hypperpolerization

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Myoclonic

sudden or split second, contraction of a muscle or group of muscles

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Lennox Gastaut syndrome

difficult to control seizure disorder where pt usually has myoclonic, atonic, absence and tonic seizures

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Pathophysiology of seizures

not well understood, imbalance between excitatory and inhibitory neurons

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Non-pharm treatment

surgery, ketogenic diet, vagal nerve stimulator

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Goals of AEDs

decrease seizures, minimize adverse effects of seizures

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AEDs MOA

inhibit Na channels, inhibit Ca channels, potentiate K channels, increase GABA, decrease glutamate

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Barbiturates

Phenobarbital, primidone (Mysoline), Prntobarbital (Nembutol), Methohexital (Brevitol)

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Barbiturates MOA

binds to allosteric modulation site that is present at a/B subunits of GABA, coupled to Cl channels they open in presence of GABA permitting influx of Cl and hyperpolerizes cell, barbiturates cause cl channel to stay open

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Phenobarbitol

effective in tonic-clonic, and focal seizures, DOC for neonatal seizures, IV/PO, cheap, can be monitored

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ADRs of phenobarbitol

sedation, depression of mood, cognitive impairment, hepatoxicity, lots of DIs

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Primidone (Mysoline)

major metabolite of phenobarbitol, DOC for essential tremor, second line for focal and tonic clonic, very sedating, sometimes status epilepticus, primary use for pentobarbital coma

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Phenytoin (Dilantin) MOA

Na channel blocker that binds the inactive channel and inc the time it takes to recover to the active state, prolonged recovery time limits high-freq firing, some use in antiarrythmias

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Phenytoin (Dilantin) indications

focal w/and w/out 2nd generalization, sometimes primary generalized tonic clonic, eizure prevention following neurosurgery, not effective for atonic, absence or myoclonic seizures

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Phenytoin (Dilantin)

IV/PO must drug monitor, narrow therapeutic index, nonlinear kinetics, status: load w/ 15-20 mg/kg IV/PO, maintenance 100 mg PO TID to start, normal levels 10-10 mcg/ml, adjust for protein, many DI

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Phenytoin ADRs

sedation, nausea, nystagmus, dizziness, cog impair, ataxia, SJS, hepatic toxicity aplastic anemia, gingival hyperplasia, hirsutism, folate defiency and osteopenia

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Fosphenytoin (Cerebyx)

IV prodrug of phenytoin, less ADRs, infused faster 150 mg/min, loading does 100 mg IV, IV/IM

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Benzodiazepines

Diazepam (Valium), Lorazepam (Ativan), Midazolam (Versed), Clonazepam (Klonipin), Clobazam (Onfi)

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Benzo MOA

bind to allosteric modulation site of GABA receptor, GABA linked to Cl channel, when GABA and Benzos are bound to receptors they follow more frequent opening of channels, and thus more hyperpolarization

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Clonazepam (Klonopin)

only PO, for myoclonic, atypical absence seizures of lennox Gastaut syndrome, severe ADRs limit use, CIV controlled

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Clonazepam (Klonopin) dose

.5-2 mg PO BID

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Clobazam (Onfi)

only PO, for adjunct Lennox-Gastaut, epilepsy, CIV controlled, ADRs- somnolence, pyrexia, lethargy, upper respiratory infxn

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Clobazam (Onfi) dose

based on wt, end dose 10-20 mg PO BID

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Diazepam (Valium)

PO, IV and rectal (acute at home), CIV controlled, many active metabolites, long T1/2

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Diazepam (valium) dose

10-20 mg, rectal .2 mg/kg

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Lorazepam (Ativan)

IV/PO, IV DOC for status, also acute seizures, PO rare for chronic, better options

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Lorazepam (Ativan) dose

2 mg IV until controlled, maintenence dose .5 mg PO BID

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Midazolam (Versed)

IV, refractory status last line, short T1/2 requires continuous infusion to maintain therapeutic levels, usually used for sedation

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Succinimides

Ethosuximide (Zarontin), Methsuximide (Celontin)

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Ethosuximide (Zarontin)

first absence seizure med, unknown MOA (block voltage dependent T-type Ca channels in thalamus), only effective for treatment of absence (DOC)

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ADRs of Ethosuximide (Zarontin)

GI intolerance, sedation, dizziness, irritability, aggression, and extrapyramindal symptoms

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The "Zepine" MOA

prolongs refractory period of voltage gated Na channels, inhibits voltage gated Ca channels, limits sustained high frequency neuronal firing of action potentials in a manner similar to PHT

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Carbamazepine (Tegretol)

for partial seizures, generalized tonic/clonic, trigeminal neuralgia, acute mania, migraines, not for absence, myoclonic or atonic seizures, lots of DI, induces its own metabolism

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Carbamazepine (Tegretol) dose and ADRs

200 mg BID, hyponatremia, dizziness, somnolence, ataxia, nystagmus, nausea, diplopia, SJS, leukopenia, agranulocytosis, aplastic anemia, hepatic toxicity

44

Oxycarbazepine (Trileptal)

developed to limit ADRs, metabolized to monohydroxy derivative which exerts the anticonvulsant effect, for monotherapy of add-on for focal seizures, few DI

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Oxycarbazepine (Trileptal) ADRs and dose

150 mg PO BID-600 PO BID (2400mg/day max), dizziness, somnolence, ataxia, nystagmus, nausea, diplopia, rash, hyponatremia

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Eslicarbazepine (Apriom)

brand new, 400-800 mg PO daily, for partial onset seizures as adjunct, same ADR and DIs

47

Valproate

Valproic Acid (Depakene), Divalproex (Depakote), IV/PO, broad spectrum, tonic/clonic, absense, myoclonic, focal, status, mania, migraine prevention/tx, many DI w/ other AEDs

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Valproate MOA

inc GABA at synaptic sites, inc synthesis and dec degradation, reduced sustained rapid firing consistent w/ effect on Na channels, reduces excitation mediation by NMDA type glutamate receptors, blocks voltage dependent T-type Ca in peripheral ganglion

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Valproate Dose

initial 10-15 mg/kg/day, load 1000 mg IV, max 50-60 mg/kg/day, normal maintenance 500mg PO BID, normal therapeutic 50-100 mcg/ml

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Valproate ADRs

GI upset, sedation, cog impairment, ataxia, dizziness, weight gain, hair loss, hepatotoxic, pancreatitis, thrombocytopenia, encephalopathy, teratogenicity, PCOS

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Felbamate (Felbatol)

Na channel blocker, non-NMDA glutamate receptor antagonist, use for focal seizures, Lennox-Gastaut syndrome, atonic seizures, use limited by ADRs

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Gabapentin (Neurontin)/Pregabalin (Lyrica)

increases GABA synthesis, not very effective as anticonvulsant, for neuropathic pain, renally eliminated, 300 mg PO BID up to 1200 mg PO TID, gaba very sedating, pregabalin not as much (but dea controlled?)

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Lamotrigine (Lamictal) MOA

blocks voltage dependent Na channels leading to decrease in glutamate release, blocks influx through voltage dependent Ca channel, enhancing hyperpolarizing K current

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Lamotrigine (Lamictal) uses and ADRs

monotherapy or add on for all seizure, DOC bipolar, DOC during pregnancy, mood-elevating, dizziness, migraines, tremors, SJS (but not if titrate slowly)

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Topiramate (Topamax) MOA

exact MOA unknown, likely effects Na channels, glutamate receptors and GABA

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Topiramate (Topamax) Uses/Dose

25 mg PO BID up to 400 mg/day, monotherapy/add on for focal/ tonic/clonic, add on for lennox gastaut, ineffective for ansence, migraine prevention, wt loss

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Topiramate (Topamax) ADRs

Cog impairment, sedation, behavior symptoms, peripheral paresthesis, nephrolithiasis, angle-closure glaucoma

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Zonisamide (Zonegran)

reduces current through voltage-dependent Na channels, impairs high-freq firing of action potentials, blocks T-type Ca channels, used for mono/add on for generalized seizures

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Levetiracetam (Keppra)

Unknown MOA, but unique, 500 mg PO BID up to 3000mg/day, IV/PO, focal, myoclonic, add on for status, seizure prevention in brain tumors, renally eliminated, no known DI, frequent in peds

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Levetiracetam (Keppra)

generally well tolerate, does not need to be titrated, fatigue, irritability, psychosis, depression

61

Vigabatrin (Sabril)

inhibits GABA transaminase, inc GABA, for focal/ infantile spasms (DOC), BBW for vision loss

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Ezogabine (Potiga)

unique MOA, neuronal K channel opener, stabilizes channels in open formation resulting in suppression of epileptic activity, for partial seizures, new safety alert for vision loss

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Lacosamide (Vimpat)

slow inactivation of voltage-gate Na channels, indicated for partial onset seizures, IV/PO, neuropathic pain, dizziness, HA, nausea, diplopia, dose dependent PR interval prolongation

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Rufinamide (Banzel)

prolongs refractory period of voltage-gated Na channels, for lennox-gastaut in pts >4 yo, cause sedation, nausea, HA, valproic acid will inhibit metabolism, decrease dose if using together

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Generalized tonic clonic DOC

valproate, Levetiracetam, Fosphenytoin, Lorazepam, also Phenobarbital, Carbamazepine, Oxcarbazepine, phenytoin, topiramate

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General absence DOC

ethosuximide, valproate, also levetiracetam, clonazepam, lamotrigine

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Focal or partial DOC

carbamazepine, Oxcarbazepine, levetiracetam, also phenobarbital, phenytoin, topiramate, lacosamide

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Myotonic DOC

valproate, levetiracetam, also rufinamide, clobazam

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Status epilepticus

Lorazepam, Diazepam, also fosphenytoin or phenobarb for prolonged

70

Lennox gastaut

valproate also clobazam, topiramate, rufinamide