Antiepileptics Flashcards
What is the primary mechanism of action for phenytoin, carbamazepine, oxcarbazepine, and lamotrigine, and how does this treat seizures?
Stabilize the inactive conformation of voltage-gated Na channels, which inhibits further neuronal depolarization
Of the 4 Na channel stabilizers, which is most effective and which is least effective at treating absence seizures?
Lamotrigine; phenytoin
What kind of seizures are carbamazepine and oxcarbazepine most effective at treating?
Complex partial seizures
How are the Na channel stabilizers metabolized, and what 3 symptoms of toxicity do they all exhibit?
Hepatic metabolism; toxicity = “dizzy, drunk, and double vision”
In addition to treating epileptic seizures, what conditions are phenytoin, carbamazepine, oxcarbazepine, and lamotrigine commonly used to treat?
Phenytoin: none; Carbamazepine, oxcarbazepine, and lamotrigine: bipolar disorder and neuropathic pain
Which epileptic medication is FDA approved for use in children?
Lamotrigine
Name the active metabolite of carbamazepine, which is less protein bound, causes less autoinduction, has fewer interactions, is less toxic, and has a longer half-life than carabamazepine.
Oxcarbazepine
Which highly protein-bound epileptic medication can cause interesting side effects like gingival hyperplasia, hirsutism, and a lupus-like reaction?
Phenytoin
Which epileptic medication has synergistic action with / competes with valproic acid for excretion?
Lamotrigine
What receptors does valproate likely affect, and what are 4 disorders it can be used to treat?
Affects voltage-gated Na channels and GABA receptors; used for (1) all seizures including status epilepticus, (2) bipolar disorder, (3) migraine prevention, and (4) cluster headaches long-term prevention
What receptors do vigabatrine and tiagabine affect, and by what mechanisms do they treat epilepsy?
GABA-A receptors; Vigabatrine binds GABA transaminase which slows degradation, while tiagabine inhibits GABA reuptake
What class of anxiolytic drugs can also be used to treat status epilepticus and to cause anesthesia? What receptors do they affect?
Benzodiazepines; are GABA-A agonists
Name 2 features that limit the usefulness of benzodiazepines in terms of length of usefulness.
Redistribution in the body (limits short-term use) and tolerance (limits long-term use)
How do gabapentin and pregabalin work molecularly, and what are they therefore used to treat?
Gabapentin and pregabalin are GABA analogs that inhibit presynaptic Ca influx; they are used for partial complex epilepsy and neuropathic pain
Which antiepileptic is not metabolized at all in the body, and therefore has limited absorption in the intestines, almost no side effects, and will not cause organ toxicity if “overdosed”?
Gabapentin
Compare and contrast the receptor actions of topiramate and felbamate.
Both are glutamate receptor (Ca channel) antagonists with secondary effects on voltage-gated Na channels and GABA receptors; but topiramate blocks AMPA and kainate receptors while felbamate blocks NMDA receptors
Topiramate is similar to what other anti-epileptic in that it can used for prophylaxis of migraines and cluster headaches, as well as for seizures?
Valproate
What anti-epileptic drug has a number of unusal side effects, including carbonic anhydrase activity, modest weight loss, and “word-finding” cognitive problems? What are 3 more side effects that can accompany the carbonic anhydrase activity?
Topiramate; may see mild metabolic acidosis, kidney stones, and glaucoma (treat with vitamin C, which acidifies the urine)
What anti-epileptic drug, used in medically refractory epilepsy, can sometimes cause unusal side effects of aplastic anemia and acute hepatic failure?
Felbamate
What anti-epileptic drug binds synaptic vesicle protein 2, leading to decreased neurotransmitter release?
Levetiracetam
Name 3 rare but possible side effects of levetiracetam.
Irritability, aphasia, and thrombocytopenia
What anti-epileptic drug blocks T-type calcium currents in thalamo-cortical circuits?
Ethosuximide
What disorder is ethosuximide specifically used to treat? Does it have any side effects?
Absence seizures; may cause mild side effects (ex. nausea, sedation, and irritability)
What 2 anti-epileptic drugs can be used for absence seizures and neuropathic pain?
Lamotrigine and ethosuximide
