Exam 1 - Antiepileptics Flashcards
What are the three partial/focal seizures and which is associated with impairment of consciousness?
simple partial (without), complex partial (with) and secondary generalized
Explain pathophysiology of seizures?
abnormalities in ion channel, increased ENT activity, rhythmic and repetitive hypersynchronous discharge of neurons, seizure focus
What seizures is phenytoin used for? (2)
partial and generalized tonic-clonic
Explain phenytoin pharmacokinetics? (6)
80-90% protein bound, inducer, t1/2 = 20 hrs, TPI = 10-20 ug/mL, 200-400 mg/day, excreted in urine
What is the MOA for phenytoin?
membrane stabilization by blocking Na and Ca influx
What are adverse effects of phenytoin?
gingival hyperplasia, hirsutism, osteomalacia, Hydantoin syndrome
What drug has a similar MOA and clinical uses (+mania and trigeminal neuralgia) as phenytoin?
carbamazepine
Explain carbamazepine pharmacokinetics? (6)
80% protein bound, strong inducing agent, t1/2 = 30 hrs, TPI = 6-12 mg/mL, 200-800 mg/day, excreted in urine
What are adverse effects of carbamazepine?
congenital malformation, hyponatremia and water intoxication, blood dyscrasias (fetal aplastic anemia)
Explain valproate pharmacokinetics? (2)
t1/2 = 15 hrs, excreted in urine
What seizures is sodium valproate used for? (2)
absence, myoclonic
What are adverse effects of sodium valproate?
increased appetite and weight gain, hepatotoxicity, neural tube defects
What is the MOA for levetiracetam?
non-competitive AMPA receptor antagonist
What seizures is levetiracetam used for?
all
What is the dosing for immediate release levetiracetam?
500 mg bid
What is the dosing for extended release levetiracetam?
1 g qd
Explain pharmacokinetics for lamotrigine? (3)
does not affect hepatic enzymes, t1/2 = 24 hrs, excreted in urine
What is the MOA for lamotrigine?
inhibits amino acid release by Na channel blockade
What are adverse effects of lamotrigine?
rash, somnolence
What is the MOA of gabapentin?
structural analogue of GABA
Explain pharmacokinetics for lamotrigine? (4)
not protein bound, does not affect hepatic enzymes, t1/2 = 5-7 hrs, excreted unchanged in urine
What seizures is gabapentin used for?
adjunct with other antiepileptics
What are adverse effects of gabapentin?
somnolence, ataxia, nystagmus
Explain pharmacokinetics of topiramate? (4)
9-17% protein bound, does not affect hepatic enzymes, t1/2 = 18-24 hrs, excreted unchanged in urine
What is the MOA of topiramate?
blocks sodium channels
What are adverse effects of topiramate?
psychological or cognitive dysfunction (“dopamax”), weight loss, urolithiasis, bilateral paresthesias
Explain pharmacokinetics of vigabatrin? (4)
not protein bound, does not affect hepatic enzymes, t1/2 = 4-7 hrs, excreted unchanged in urine
What is the MOA for vigabatrin?
inhibits GABA metabolizing enzyme
What seizures is vigabatrin used for?
infantile spasms
What are adverse effects of vigabatrin?
visual field defects, psychosis, and depression
Explain pharmacokinetics of zonisamide? (4)
40% protein bound, does not affect hepatic enzymes, t1/2 = 50-68 hrs, metabolized by liver
What is the MOA for zonisamide?
prolongation of sodium channel inactivation
What seizures is zonisamide used for?
add-on therapy for partial seizures
What are adverse effects of zonisamide?
drowsiness, ataxia, headache, N/V
Explain pharmacokinetics of tiagabine? (3)
96% protein bound, t1/2 = 4-7 hrs, metabolized by liver
What is the MOA of tiagabine?
inhibits GABA uptake
What are adverse effects of tiagabine?
asthenia, sedation, dizziness, mild memory impairment
What are reasons for failure of antiepileptics? (4)
improper diagnosis, incorrect drug, inadequate dose, compliance
