E1: Anticonvulsants Flashcards
What is the main goal of anticonvulsants?
Since a blockage of GABA receptors causes seizures, the goal is to increase GABA activity
-OR since activation of glutamate can lead to seizures, the goal is to decrease glutamate activity
What are the 4 mechanisms in which anticonvulsants can increase GABA activity?
- block GABA re-uptake
- inhibit GABA metabolism
- Stimulate GABA receptors
- Binds synaptic vesicular protein
What are the two main channels that are inhibited by decreased glutamate activity?
Na+ and Ca+ channels
What are the three anticonvulsants that induce CYP450?
Phenytoin, Carbamazepine, and phenobarbital
What are the uses of phenytoin and fosphenytoin?
- Partial seizures and generalized tonic-clonic seizures.
- Not effective of absence seizures
What is the MOA of Phenytoin and Fosphenytoin?
Prolongs inactivation of Na Channels by decreasing glutamate activity
Can phenytoin or fosphenytoin be injected?
Fosphenytoin
How is Phenytoin and fosphenytoin elimated?
-Elimination is 1st order at low doses and zero order at therapeutic and higher doses
What are the common side effects of Phenytoin?
- Gingival hyperplasia
- nystagmus, diplopia, ataxia, sedation
- skin rash (risk of SJS)
- Pregnancy category D
What is the DOC for partial seizures?
Carbamazepine
What are the uses of Carbamazepine?
- DOC for partial seizures
- generalized tonic-clonic seizures
- Bipolar disorder
- Trigeminal neuralgia
What is the MOA of Carbamazepine?
-Blocks Na channels by decreasing glutamate activity
What are the important pharmacokinetics associated with carbamazepine?
- Induces CYP450
- induces its own metabolism
What are the drug interactions associated with Carbamazepine?
- Increases metabolism of multiple anticonvulsants, haloperidol, and oral contraceptives
- metabolism increased by phenobarbital and phenytoin
- metabolism is inhibited by cimetidine, fluoxetine, and Valproic acid
What are the common side effects associated with carbamazepine?
- SJS (test for HLA-B gene)
- diplopia, ataxia, GI upset, drowsiness, aplastic anemia, and agranulocytosis
- Pregnancy category D
What is the MOA of Lamotrigine?
-inactivation of Na channels by decreasing glutamate activity
What are the uses of lamotrigine?
- partial seizures
- may be effective against myoclonic and absence seizures in children
- bipolar disorder
What are the important pharmacokinetics associated with lamotrigine?
- inducers of CYP450 will increase metabolism
- half life is doubled by valproic acid
What are the common side effects of lamotrigine?
- CNS (dizziness, headache, ataxia, diplopia)
- nausea and vomiting
- SJS
- Pregnancy category C
What are the uses of Topiramate?
- Partial and generalized tonic clinic seizures
- may also be effective for absence seizures
- migraine prevention
What is the MOA of Topiramate?
Blocks Na channels by decreasing glutamate activity
What are the common side effects of Topiramate?
- acute myopia and glaucoma
- dizziness, sedation, nervousness, confusion