Anticonvulsants II Flashcards
What are the general adverse side effects of antiepileptic drugs?
Ataxia Nystagmus HA Depression Sedation
How are antiepileptic drugs metabolized?
hepatic MES system
Abrupt withdrawal of antiepileptic drugs has the potential for what to happen?
Inducing seizures
Why do antiepileptics cause a decrease in efficacy of oral contraceptives?
Induces cytochrome p450
What is the safest antiepileptic drug to take during pregnancy?
Phenobarbital
What is the MOA of hydantoins? (3)
- Blocks and prolongs the inactivated state of voltage-gated Na channels
- Decreases glutamate release
- Enhances GABA release
What type of antiepileptic drug is phenytoin?
Hydantoin
What type of antiepileptic drug is Fosphenytoin?
Hydantoin
What is the major difference between the Hydantoins Phenytoin and fosphenytoin?
Fosphenytoin is more soluble prodrug
What are the pharmacokinetics of Hydantoins (absorption, state in blood, what type of elimination)?
Variable absorption
Highly bound to protein albumin
Zero order elimination
What type of drugs cause the release of albumin bound hydantoins?
Acidic drugs
What is the route of metabolism for Hydantoins?
Metabolized in liver by MES system
Induction of p450 enzymes
Can zero order elimination be saturated?
yes
At low doses, what is the relationship between plasma concentration, and dose? High doses?
Low = relatively linear High = Nonlinear
true or false: phenytoin can be used to treat status epilepticus
true
What are the idiosyncratic side effects of phenytoin?
Gingival hyperplasia
Osteomalacia
Hirsutism
What is fetal hydantoin syndrome?
Teratogenic effects like cleft palate,
What are the two drugs that interfere with Phenytoin metabolism?
Warfarin
barbiturates (high concentration)
What are the two drugs that increase phenytoin metabolism?
Barbituates (low dose)
Carbamazepine
Lower pH can cause the release of phenytoin from albumin. What are the two drugs and one condition that can cause this?
ASA
Valproic acid
Renal failure
What is the MA of carbamazepine?
Inhibition of voltage gated Na channels
Decreases E release
How is carbamazepine metabolized?
Hepatic MES
Potent induce of MES p450s
How well is carbamazepine absorbed?
Well absorbed
What is the MOA of oxcarbazepine?
Derivative of carbamazepine
Inhibits Na channels and decreases E release
What is the major difference between Oxcarbazepine and carbamazepine?
fewer drug interactions
What are the clinical uses of carbamazepine?
generalized szs
Partial szs
Trigeminal neuralgia
What are the side effects of carbamazepine?
CNS depression
Aplastic anemia
SIADH
What are the three major drug interactions of carbamazepine?
Phenytoin
valproate
Phenobarbital