Exam 1 - Antiepileptics

Question 1

What are the three partial/focal seizures and which is associated with impairment of consciousness?

Answer 1

simple partial (without), complex partial (with) and secondary generalized

Question 2

Explain pathophysiology of seizures?

Answer 2

abnormalities in ion channel, increased ENT activity, rhythmic and repetitive hypersynchronous discharge of neurons, seizure focus

Question 3

What seizures is phenytoin used for? (2)

Answer 3

partial and generalized tonic-clonic

Question 4

Explain phenytoin pharmacokinetics? (6)

Answer 4

80-90% protein bound, inducer, t1/2 = 20 hrs, TPI = 10-20 ug/mL, 200-400 mg/day, excreted in urine

Question 5

What is the MOA for phenytoin?

Answer 5

membrane stabilization by blocking Na and Ca influx

Question 6

What are adverse effects of phenytoin?

Answer 6

gingival hyperplasia, hirsutism, osteomalacia, Hydantoin syndrome

Question 7

What drug has a similar MOA and clinical uses (+mania and trigeminal neuralgia) as phenytoin?

Answer 7

carbamazepine

Question 8

Explain carbamazepine pharmacokinetics? (6)

Answer 8

80% protein bound, strong inducing agent, t1/2 = 30 hrs, TPI = 6-12 mg/mL, 200-800 mg/day, excreted in urine

Question 9

What are adverse effects of carbamazepine?

Answer 9

congenital malformation, hyponatremia and water intoxication, blood dyscrasias (fetal aplastic anemia)

Question 10

Explain valproate pharmacokinetics? (2)

Answer 10

t1/2 = 15 hrs, excreted in urine

Question 11

What seizures is sodium valproate used for? (2)

Answer 11

absence, myoclonic

Question 12

What are adverse effects of sodium valproate?

Answer 12

increased appetite and weight gain, hepatotoxicity, neural tube defects

Question 13

What is the MOA for levetiracetam?

Answer 13

non-competitive AMPA receptor antagonist

Question 14

What seizures is levetiracetam used for?

Answer 14

all

Question 15

What is the dosing for immediate release levetiracetam?

Answer 15

500 mg bid

Question 16

What is the dosing for extended release levetiracetam?

Answer 16

1 g qd

Question 17

Explain pharmacokinetics for lamotrigine? (3)

Answer 17

does not affect hepatic enzymes, t1/2 = 24 hrs, excreted in urine

Question 18

What is the MOA for lamotrigine?

Answer 18

inhibits amino acid release by Na channel blockade

Question 19

What are adverse effects of lamotrigine?

Answer 19

rash, somnolence

Question 20

What is the MOA of gabapentin?

Answer 20

structural analogue of GABA

Question 21

Explain pharmacokinetics for lamotrigine? (4)

Answer 21

not protein bound, does not affect hepatic enzymes, t1/2 = 5-7 hrs, excreted unchanged in urine

Question 22

What seizures is gabapentin used for?

Answer 22

adjunct with other antiepileptics

Question 23

What are adverse effects of gabapentin?

Answer 23

somnolence, ataxia, nystagmus

Question 24

Explain pharmacokinetics of topiramate? (4)

Answer 24

9-17% protein bound, does not affect hepatic enzymes, t1/2 = 18-24 hrs, excreted unchanged in urine

Question 25

What is the MOA of topiramate?

Answer 25

blocks sodium channels

Question 26

What are adverse effects of topiramate?

Answer 26

psychological or cognitive dysfunction ("dopamax"), weight loss, urolithiasis, bilateral paresthesias

Question 27

Explain pharmacokinetics of vigabatrin? (4)

Answer 27

not protein bound, does not affect hepatic enzymes, t1/2 = 4-7 hrs, excreted unchanged in urine

Question 28

What is the MOA for vigabatrin?

Answer 28

inhibits GABA metabolizing enzyme

Question 29

What seizures is vigabatrin used for?

Answer 29

infantile spasms

Question 30

What are adverse effects of vigabatrin?

Answer 30

visual field defects, psychosis, and depression

Question 31

Explain pharmacokinetics of zonisamide? (4)

Answer 31

40% protein bound, does not affect hepatic enzymes, t1/2 = 50-68 hrs, metabolized by liver

Question 32

What is the MOA for zonisamide?

Answer 32

prolongation of sodium channel inactivation

Question 33

What seizures is zonisamide used for?

Answer 33

add-on therapy for partial seizures

Question 34

What are adverse effects of zonisamide?

Answer 34

drowsiness, ataxia, headache, N/V

Question 35

Explain pharmacokinetics of tiagabine? (3)

Answer 35

96% protein bound, t1/2 = 4-7 hrs, metabolized by liver

Question 36

What is the MOA of tiagabine?

Answer 36

inhibits GABA uptake

Question 37

What are adverse effects of tiagabine?

Answer 37

asthenia, sedation, dizziness, mild memory impairment

Question 38

What are reasons for failure of antiepileptics? (4)

Answer 38

improper diagnosis, incorrect drug, inadequate dose, compliance