Anticonvulsants Flashcards
MOA: delays recovery of inactivated Na+ channels
Use: Partial & tonic-clonic seizures
lamotrigine (Lamictal)
zonisamide (Zonegran)
carbamazepine (Tegretol)
phenytoin (Dilantin)
Int: oral contraceptives
MOA: reduces recovery time of Na+ channels & reduces low-threshold T-type Ca2+ currents
Use: absence, partial & tonic-clonic seizures
Valproic acid (Depakene)
Int: phenytoin, phenobarbital, lamotrigine, lorazepam
Caution: teratogen -> no use in pregnancy
Use of Valproic acid in bipolar disorder
depletes inositol, stabilizes mood
MOA: reduces voltage-gated Na+ currents & activates GABAa receptors (increases Cl- influx causing hyperpolarization); limits activation of AMPA receptors
Use: partial or tonic-clonic seizures & adult migraine headache
Adverse: fatigue, weight loss, renal calculi
changes taste of carbonated beverages
Topiramate (Topamax)
Int: oral contraceptives
MOA: reduces low-threshold T-type Ca2+ currents in thalamic neurons
Use: absence seizures
Adverse: nausea, vomiting, anorexia, drowsiness,
some tolerance, bone marrow suppression
Ethosuximide (Zarontin)
benzodiazepine anticonvulsant
MOA: increases the frequency of Cl- channel opening increasing GABAa synaptic inhibition
Use: absence & myoclonic seizures in children/ status epilepticus
“Benzos are mazo and open the door over and over”
Adverse: drowsiness, lethargy, tolerance, behavioral disturbances
clonazepam (Klonipin)
diazepam (Valium)
Note: clorazepate is also approved but not on our SG
barbiturate anticonvulsive
MOA: enhances activation of the GABAa receptor and therefore synaptic inhibition by increasing the duration of the Cl- channel opening
Use: tonic-clonic seizure
Adverse: drowsiness
“Barb holds the door open”
phenobarbital (Luminal)
primidone (Mysoline)
*note: primidone is metabolized to phenobarbital
can be used to activate GABAa receptors without GABA bound and can be used for full surgical anesthesia
high dose barbiturates
anticonvulsive that inhibits the GABA transporter GAT-1, reducing GABA uptake into neurons and glia
Use: add on therapy for refractory partial seizures in adults
Adverse: dizziness, somnolence, tremor
tiagabine (Gabitril)
Int: phenobarbital, phenytoin, carbamazepine
centrally-acting GABA agonists with high lipid solubility
Use: partial seizures
Adverse: somnolence, dizziness, ataxia, pregnancy category C
Gabapentin (Neurontin)
pregabalin (Lyrica)
*note: can also be used for neuropathic pain (shingles)
Conventional anticonvulsive drug that can be used for all types of seizures
Valproate
newer anticonvulsive drug that can be used for all types of seizures
Lamotrigine
*note: generally better tolerated with less drowsiness. Rash limits its use.
Caution with phenytoin
It follows first order kinetics (concentration is related to dose) at low doses and the dose is not saturable. However, with increasing the dose as blood levels rise to therapeutic range approaches the capacity for the liver to metabolize the drug (zero order kinetics meaning there is not relationship between dose & concentration in the blood): small increases in dose can easily cause toxicity.
Note: also highly albumin-bound and can be displaced by valproate
drug induces CYP that metabolizes it
carbamazepine
Metabolism notes of anticonvulsives
carbamazepine can induce metabolism of phenytoin and vice versa
Lamotrigine metabolism is inhibited by valproate
