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35 Cards in this Set
- Front
- Back
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Define a partial seizure
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A partial seizure is initiated in localized regions of the cortex and often originate in a region of an anatomic abnormality (tumor, trauma, stroke, ect.)
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What are the subtypes of partial seizures?
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1) simple partial: no loss of consciousness, last less than one minute
2) complex partial: impaired or loss of consciousness, less than 2 minutes 3) partial with secondary generalized: Either of the above that progresses to a tonic-clonic seizure |
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Define a generalized seizure
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Neocortical discharges that synchronize with discharges in the thalamus and are usually considered to be congenital; they involve both hemishperes
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What are the subtypes of generalized seizures?
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1) Absence: abrupt onset or impaired consciousness with duration less than 30 seconds
2) myoclonic: contraction of muscles that may be generalized or local 3) tonic 4) tonic-clonic |
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What percentage of patients are refractory to seizure medication?
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25%
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What anti-seizure drugs work by inhibiting voltage-gated Na channels?
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phenytoin, carbamazapine, valproate, topiramate, lamotrigine, zonisamide
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Describe the therapeutic uses of phenytoin. What is it's mechanism of action?
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Phenytoin inhibits depolarization by inhibiting the voltage-gated Na channel. It is used to treat partial and generalized tonic-clonic seizures
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Describe the side effects of phenytoin
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1) Nystagmus and diplopia
2) Hirsutism 3) Facial coarsening 4) Gingival hyperplasia 5) megaloblastic anemia (decreased folate absorption) ** |
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What drug interactions are associated with phenytoin?
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Phenobarbital and carbamazapine decrease the plasma levels of phenytoin by inducing CYPs, while sulfonamides and phenylbutazone increase plasma levels by displacing them from proteins. Valproate increases serum concentration due to competition for hepatic metabolism
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Describe the teratogenic effects of phenytoin
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It results in fetal hydantoin syndrome, which consists of mental retardation and characteristic facial features along with hypoplastic distal phalanges
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What is the mechanism of action of carbamazapine?
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It stabilizes the inactive form of the voltage-gated Na channel and also potentiates GABA-A post synaptic receptors
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Describe the therapeutic uses for carbamazapine
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It is the drug of choice for partial seizures and is also first-line for generalized tonic-clonic seizures; it can be used for mood stabilization in bipolar disorder
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Describe the side effects and toxicity associated with carbamazapine
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1) diplopia
2) ataxia 3) aplastic anemia (rare but potentially fatal) |
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What is the mechanism of action of valproate?
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It has multiply mechanisms:
1) voltage-gated Na channel inhibition 2) increase in presynaptic GABA 3) inhibition of Ca voltage-gated channels in the thalamus |
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Describe the therapeutic uses of valproate
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1) All types of seizures--especially myoclonic
2) mood stabilizer in bipolar disorder 3) migraine prophylaxis |
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Describe the toxicity associated with valproate
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1) nausea and gastric upset
2) hepatotoxicity - important to check liver enzymes in the first 4 months of therapy |
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Describe the mechanism of action of topiramate
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1) inhibits voltage-gated Na channels
2) potentiates activity of post-synaptic GABA receptors |
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What are the therapeutic uses of topiramate?
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They are similar to phenytoin (partial and generalized tonic-clonic seizures) and are most often used to treat partial seizures
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What are the side effects of topiramate?
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1) fatigue, confusion
2) paresthesias 3) glaucoma |
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What is the mechanism of action of lamotrigine?
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It inhibits both voltage-gated Na channels and voltage-gated Ca channels in the thalamus
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Describe the toxicities associated with lamotrigine
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Rashes and Stevens-Johnson syndrome (mostly in children, contraindicated for that population)
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What are the therapeutic uses of lamotrigine?
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They are similar to phenytoin (partial and generalized tonic-clonic)
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What is the mechanism of zonisamide?
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It inhibits Na and Ca voltage-gated channels
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What is the therapeutic use of zonisamide?
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It is used as an adjunct in refractory partial seizures
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Toxicity associated with zonisamide
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rashes and renal calculi
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What anti-seizure drugs work primarily by enhancing the GABA-mediated Cl- flux?
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Phenobarbital, primidone, tigabine, and gabapentin
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What is the mechanism of action of phenobarbital and it's metabolite primidone?
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They enhance the GABA mediated chloride ion flux
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What is the therapeutic use of phenobarbital?
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It is used to treat partial and generalized tonic-clonic seizures. It is tried on almost any kind of seizure
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What is the mechanism of action of Tigabine?
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It inhibits GABA reuptake
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What is the therapeutic use of Tigabine?
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It is used as an adjunct in treatment of partial seizures
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What is the mechanism of action of ethosuximide?
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It blocks the voltage-gated channels in the thalamus
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What drug is the first-line and drug of choice in the treatment of absence siezures?
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Ethosuximide
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What drug is the drug of choice for the treatment of myoclonic seizures?
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Valproate
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What is the mechanism of action of gabapentin and what is it used to treat?
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It enhances the concentration of presynaptic GABA, but the molecular target is unknown; it is a mjor treatment for neuropathic pain
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Describe the treatment of status epilepticus
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Initial seizure activity is treated with IV diazepam, followed by IV phenytoin
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