Antiepileptic Drugs Flashcards
In what ways can AEDs limit excitability?
- block voltage gated sodium channel
- block voltage gated calcium channel
- block glutamate receptors
In what ways can AEDs enhance inhibition?
- encourage the GABA system
What four drugs work on the Na channel, and what is their MOA?
- phenytoin
- carbamazepine
- oxcarbamazepine
- lamotrigine
- bind to and stabilize inactive state of channel, which inhibits recurrent depolarization
Sodium channel blockers are effective for what types of seizures?
- simple or complex partial (more effective)
- general tonic-clonic
What two drugs are used to treat absence seizures?
- ethosuximide and valproic acid
What drugs are used to treat status epilepticus?
- lorazepam, diazepam
- phenytoin
- fosphenytoin
What two drugs are glutamate receptor blockers and which specific receptors do they act on?
- topiramate: AMPA/kainate receptor blocker (toxicity: difficulty finding words)
- felbamate: NMDA receptor blocker (used for medically refractive epilepsy, SE: aplastic anemia, acute hepatic failure)
What class of drug are gabapentin and pregabalin (what’s in a name?) and how do they work? Even though they can be used for partial complex epilepsy, what are they more commonly used for?
- GABA analogs
- block presynaptic influx of Ca
- mostly used for neuropathic pain
What is unique about the metabolism of Na channel stabilizers?
all induce hepatic enzymes (upregulate P450) which causes autoinduction and heteroinduction
- over time will need to increase dose to get same effect
- may cause contraceptive failure
How are carbamazepine and oxcarbamazepine related and why would oxcarb be chosen over carb?
- carbamazepine has a toxic epoxide metabolite
- oxcarbamazepine is designed to bypass this metabolite
- however, oxcarbamazepine has its own metabolite that can cause its own toxicity but the side effects are generally less
What are the common toxicities and less common side effects of Na channel blockers?
- sedation, ataxia, diplopia (drunk, dizzy, double vision)
- Stevens-Johnson, hepatic enzyme elevation, myelosuppression
What is unique about phenytoins pharmacokinetics?
- a physiological dose can induce zero order kinetics, so blood levels can drastically change with small adjustments to dose
What are two unique side effects of phenytoin?
- gingival hyperplasia
- hirsutism
Which sodium channel blocker can be used in children? How must this drug be started, and what might it cause?
- lamotrigine
- start drug very slowly or may cause Stevens Johnson
How does valproic acid work? What are some adverse reactions?
- affects Na channels and GABA system
- tremor, hair loss, TERATOGENICITY
