Anti-Convulsants Flashcards
Carbamazepine mechanism
Increases Na+ channel inactivation
Clonazepam mechanism
Increases GABA action (benzo) Used for: - absence seizures - myoclonic seizures - infantile spasms
Diazepam mechanism & use
Increases GABA action (benzo)
First line for acute status epilepticus
Ethosuximide mechanism
Blocks thalamic T-type Ca2+ channels; used for treating absence seizures
Felbamate Toxicity
Causes aplastic anemia and severe hepatitis at unexpectedly high rates–> recommended to use it only for refractory cases
Gabapentin mechanism
Designed as GABA analog, but primarily inhibits high voltage-activated Ca2+ channels
Lamotrigine mechanism
Blocks voltage-gated Na+ channels
Lamotrigine Toxicity
Life-threatening dermatitis (steven-johnson syndrome)
Phenobarbital mechanism
Increases GABA action (barbituate)
Phenytoin mechanism and use
Increases Na+ channel inactivation
Good alternatives are available so it is no longer used as a first line drug
Topiramate mechanism
Blocks Na+ channels and increases GABA action
Valproic acid mechanism
Increases Na+ channel inactivation and increases GABA concentration
Tonic-Clonic Grand-Mal Seizure
prolonged duration with loss of consciousness
Absence Seizures
loss of consciousness and amnesia (from less than 10s to 45 seconds)
Myoclonic seizures
brief shock-like muscle contractions in extremities
Simple Partial
focal onset in cerebral cortex; seizures lasting from 30s to 60s with no loss of consciousness. Basically this is an aura.
Complex Partial
focal onset in cerebral cortex; seizures lasting from 30s to 2 min with loss of consciousness
3 ways that anti-convulsants work:
- Enhances GABAergic transmission in the CNS
- Reduces excitatory/glutamatergic transmission in the CNS
- Reduces neuronal excitability by targeting ion channels
Gabapentin Toxicity/SEs
Can exacerbate myoclonic seizures
Causes somnolence, dizziness, and ataxia
Topiramate SEs
somnolence, fatigue, dizziness, cognitive slowing, psychiatric symptoms, and WEIGHT LOSS.
Ethosuximide Toxicity
EFGH: -Ethosuximide -Fatigue -GI distress -Headache Rare cases--> rash, Steven-Johnson Syndrome, and bone marrow depletion
Valproic Acid Use
Used for:
- partial seizures (simple and complex)
- tonic-clonic (first line w/ carbamazepine & phenytoin)
- absence seizures (ethosuximide is first line)
- myoclonic seizures
Valproic Acid Toxicity
Hepatotoxicity (rare, but fatal within 4 months– measure LFTs)
Birth defects (spina bifida, cardiovascular, orofacial, and digital defects)
Weight gain & tremor
Anti-convulsants and Oral Contraception
Majority of anticonvulsant medications that induce liver enzymes (e.g. phenytoin, carbamazepine, phenobarbital) do reduce the efficacy of oral contraceptives
Anti-convulsants and Vitamin K
vitamin K supplements during the last 2-4 weeks of gestation recommended to decrease the risk of coagulation problems and cerebral hemorrhage in the newborn
Phenytoin Toxicity
Nystagmus, diplopia, ataxia, sedation, gingival hyperplasia, hisutism, megaloblastic anemia, teratogenesis (fetal hydantoin syndrome), SLE-like syndrome, induction of Cytochrome P450, lymphadenopathy, SJS, and osteopenia
What drugs may exacerbate absence seizures?
Phenytoin, Phenobarbital, and Carbamazepine
Carbamazepine Toxicity
Diplopia, ataxia, blood dyscrasias (agranulocytosis, aplastic anemia), liver toxicity, teratogenesis, induction of cytochrome P450, SIADH, SJS
–> Blood counts and LFTs should be done often!
Phenobarbital Toxicity
Sedation, tolerance, dependence, induction of cytochrome P450
Tolerance–> toxicity (often in children)
What anti-convulsant is contraindicated in pregnancy?
Valproic Acid due to risk of neural tube defects
