Neuro Drugs from Textbook Chart Flashcards
What is the MOA for Phenytoin/Fosphenytoin?
Na Channel Blocker
What are the kinetics of Phenytoin/Fosphenytoin?
*Decreases synaptic release of glutamate and increases release of GABA
*At therapeutic levels, the major action is to block Na+ channels and inhibit the generation of rapidly repetitive Aps
Oral absorption nearly 100%
IM absorption unpredictable
Fosphenytoin is well absorbed IV
Highly protein bound
Accumulates in the brain, liver, muscle, and fat
No active metabolites (all inactive)
Excreted in urine
Elimination is dose-dependent (FIRST ORDER KINETICS, increases in the dose after the liver has reached max capacity can result in toxicity)
Half-life: 12-36 hrs
Average 24 hrs for most pts
5-7 days to reach a steady state after each dose change (4 half-lives to reach steady state)
At high doses, it may take as long as 4-6 weeks
What are the clinical applications for Phenytoin/Fosphenytoin?
*Partial seizures
*Generalized tonic-clonic seizures
What are the S/Sx of toxicity associated with Phenytoin/Fosphenytoin?
nystagmus, diplopia, ataxia, sedation, gingival hyperplasia, hirsutism
Nystagmus and loss of ocular movements are early signs (do not indicate need to decrease dose)
Diplopia and ataxia are most common dose related adverse effects requiring dose adjustments
Sedation occurs only at considerably high levels
Gingival hyperplasia
Hirsutism (male patterned hair growth in women)
What are the S/sx associated with long-term use of Phenytoin/Fosphenytoin?
Coarsening of facial features, mild peripheral neuropathy (diminished deep tendon reflexes in the lower extremities), osteomalacia, vitamin D deficiencies, low folate levels, megoblastic anemia (inhibition of DNA synthesis during RBC production)
What drug interactions occur with Phenytoin/Fosphenytoin?
Interactions with phenobarbital, carbamazepine, topiramate, steroids, oral contraceptives
What is the MOA for Carbamazepine?
Na Channel Blocker
What are the kinetics for Carbamazepine?
Rapidly absorbed orally (bioavailability 75-85%)
Peak levels in 4-5hrs
Metabolized in the liver
Half-life: 25-65hrs
What are the clinical applications for Carbamazepine?
Focal seizures
Focal-to-bilateral tonic-clonic seizures
Trigeminal neuralgia
What are the toxicity S/Sx for Carbamazepine?
nausea, diplopia, ataxia, hyponatremia, headache
What drug interactions occur with Carbamazepine?
Interactions with phenytoin, valproate, fluoxetine, verapamil
What is the MOA for Valproate?
Unknown
What are the kinetics for Valproate?
Nearly complete (>90%) absorption
Metabolized in liver
What are the clinical applications for Valproate?
Generalized tonic-clonic seizures
Focal seizures
Absence seizures
Myoclonic seizures
Other generalized seizure types
Migraine prophylaxis
What are the toxicity S/Sx for Valproate?
nausea, tremor, weight gain, hair loss, teratogenic, hepatotoxic
What are the drug interactions associated with Valproate?
Interactions with phenobarbital, phenytoin, carbamazepine, lamotrigine
What is the MOA for Lamotrigine?
Na Channel Blocker
What are the Kinetics associated with Lamotrigine?
Nearly complete (>90%) absorption
Peak levels in 1-3hrs
Extensively metabolized, no active metabolites
T1/2 = 8-35hrs
What are the clinical applications for Lamotrigine?
Focal seizures
Generalized tonic-clonic seizures
Absence seizures
Other generalized seizures
Bipolar depression
What are the toxicity S/Sx of Lamotrigine?
dizziness, headache, diplopia, rash