Anti-epileptics Flashcards
What is the MOA of phenytoin?
Inhibit VG fast Na+ channel in inactivated state on presynaptic glutamate neuron (same as local anesthetics and Class Ib anti-arrhythmia drugs)
What are the dose-related ADRs of phenytoin in adults?
Diplopia, ataxia, dizziness, nystagmus, tremor, sedation
What are the non-dose-related / chronic use ADRs of phenytoin (unique to phenytoin) in adults?
Gingival hyperplasia and hirsutism
OD of phenytoin is what type of elimination?
Zero-order elimination
What is the definition of zero-order and first-order elimination?
Zero-order elimination is a constant rate of metabolism independent of drug concentration (concentration, same plasma conc. / time, linear line). First-order elimination is rate of metabolism proportional to drug concentration where half life is constant (percentage, different conc. / time, exponential / curved line).
What are the zero-order elimination drugs?
Phenytoin, high-dose aspirin, and alcohol
Which type of elimination allows for the drug to accumulate in the body because it is not efficient?
Zero-order elimination
What is the MOA of carbamazepine?
Inhibit inactivated VG fast Na+ channel
What are the ADRs of carbamazepine in adults?
SIADH, SJS, and agranulocytosis (reduced WBC)
Besides convulsion, carbamazepine is used to treat _____ and _____.
Trigeminal Neuralgia, mania
What are the ADRs of carbamazepine in the fetus?
Cleft lip / palate and spina bifida
What are the ADRs of phenytoin in the fetus?
Fetal Hydantoin Syndrome (signs include microcephaly, growth delay, mental retardation, developmental delay, and craniofacial dysmorphic features; hydantoin old name for phenytoin)
What are the 3 MOAs for valproic acid?
- Inhibit VG fast Na+ channels in inactive state 2. Blocks GABA ransaminase (decrease degradation, increase GABA) 3) blocks VG T-type (transient) Ca2+ channel in Thalamus (glutamate neuron)
Which drug is known to be the universal treatment for seizures since it can treat all types?
Valproic acid
What are the 2 uses of Valproic acid in addition to treating seizures?
Treatment of mania, migraine prevention
What ADR in the fetus occurs if mother takes Valproic acid (like all anti-convulsants)?
Spina bifida
To prevent spina bifida in a woman trying to get pregnant, what do you do?
Give her folate supplements 1 month before and 3 months after the pregnancy.
When do you use ethosuximide?
Absence seizure
How do you ID an absent seizure on EEG?
3 HZ spike with slow wave about 3-4 seconds
What is the MOA of ethosuximide?
Blocks VG T-type (transient) Ca2+ channel in Thalamus (glutamate neuron)
What is the ADR of ethosuximide?
swollen joints, depression, liver damage, kidney damage, drug reation (thiol)
What is the MOA of lamotrigine?
AMPA receptor (glutamate) antagonist
What is the ADR of lamotrigine?
SJS
Lamotrigine is used to treat _____ seizures.
General tonic-clonic (grand-mal)
Besides Valproic acid, what other two anti-convulsants can be used to prevent migraines?
Lamotrigine and Topiramate
What is the MOA of felbamate?
NMDA (glutamate) receptor blocker (potentiate GABA A receptor)
Though all the all anti-convulsant drugs can cause aplastic anemia, which one is considered to be the #1 worst offender of the ADR?
Felbamate
What other ASR, besides aplastic anemia, can be caused by Felbamate?
Liver toxicity
What is the mechanism of Gabapentin?
N-type presynaptic VG Ca2+ channel blocker (glutamate neuron, increase GABA release)
Other than treating convulsions, what can Gabapentin be used for?
Postherpetic neuralgia (shingles)
Which anti-convulsant drugs inhibit P450?
Valproic acid
Which anticonvulsant drugs induce P450?
All of them EXCEPT Valproic acid
Which drugs cause alopecia?
Valproic acid
Which drugs anti-convulsant, anti-cancer, anti-HIV, and anti-PCP/PCJ cause pancreatitis respectively?
Valproic acid, asparginase, didanosine, Pentamidine
Which drugs cause spina bifida and which one has higher incidence?
valproic acid > carbamazepine
Which drugs treat absence seizure?
ethosuximide and valproic acid
Which drugs first to treat status epilepticus (work fast to stop immediately)?
Diazepam and Lorazepam (BZDs)
What are the drugs for maintained treatment (long term use)?
Barbituates and Phenytoin
What drugs are used in children with febrile convulsion?
First Diazepam to stop convulsion then second acetaminophen to reduce fever
What drugs for general tonic clonic seizure?
Valproic acid, carbamazepine
Phenytoin, lamotrigine, topiramate
What are the ADRs of Pentamidine?
Reduces blood Ca2+ causing painful muscle spasm and acute pancreatitis
What methods should you do to reduce a fever causing febrile convulsion in a child if acetaminophen is not used?
Warm water bath, 30% alcohol bath, or put in air conditioned room
