Antiepileptic Drugs

Question 1

Nonpharm tx for seizure

Answer 1

Surgery
Vagal nerve stimulator implantation
Ketogenic Diet

Question 2

MOA for antiepileptic drugs

Answer 2

effect Na and Ca channels which leads to stabilization of neuronal membranes > enhance inhibitory NTs (GABA) which calms the CNS and decrease excitatory NTs (glutamate and aspartate)
leads to increase seizure threshold and inhibition of the spread of abnormal discharges

Question 3

Acute AE (2 categories)

Answer 3

Concentration related: MC, increase drug levels increases AEs, NOT PERMANENT, see at peak concentrations or throughout the day, try lowering dose, change schedule or D/C med
Idiosyncratic: more rare, not related to dose, may be permanent, seen throughout the day, need to D/C med and tx AE

Question 4

Carbamazepine important info

Answer 4

Brand: Tegretol
MOA: Na channel
AEs: *diplopia, *hyponatremia, *leukopenia, ataxia
TR: 4-12 mcg/ml
DI: CYP2C8, 3A/4 substrate AND CYP1A2, 2C, 3A/4 inducer auto-inudction

Question 5

Felbamate important info

Answer 5

MOA: excitatory AA inhibition
AEs: N/V, *aplastic anemia, *hepatic failure; usually used for refractive pts

Question 6

Gabapentin important info

Answer 6

MOA: increase GABA-ergic inhibition, decrease glutamate
AEs: sedation, dizziness, ataxia, wt gain, *potential for misuse d/t euphoria w/ high dose
DI: renally eliminated so no dg intx

Question 7

Lamotrigine important info

Answer 7

MOA: Na channel, decrease glutamate
AEs: *rash, ataxia, tremor, *start at low dose and titrate up to avoid rash

Question 8

Phenobarbital important info

Answer 8

MOA: increase GABA-ergic inhib.
AEs: *sedation, aggression in adults and hyperactivity in kids
T1/2: 36-136 hours half life for adults
DI: CYP1A2,2B6,2C,3A/4, 3A5-7 inducer

Question 9

Phenytoin important info

Answer 9

Brand: Dilantin
MOA: Na channel
AEs: *ataxia, *nystagmus, osteoporosis, sedation, *gingival hyperplasia, *hirsutism
TR: 10-20 mcg/ml free; 1-2 mcg/ml
DI: CYP2C9, 2C19, substrate; CYP1A2, 2B6, 2C, 3A/4, 3A5-7 inducer; highly protein bound
*needs a vehicle so you have to put it in solution

Question 10

Pregabalin important info

Answer 10

MOA: Ca channel
AEs: *dizziness, somnolence, ataxia, *wt gain, *abnormal thinking
DI: non renally eliminated

Question 11

Topiramate important info

Answer 11

MOA: Na channel
AEs: *decrease appetite, *decreased cognition, HA, diplopia

Question 12

Valproic Acid important info

Answer 12

Brand: Depakote
MOA: increase GABA
AEs: N/V, *tremor, *wt gain, *hepatic failure, *thrombocytopenia, pg D
TR: 50-150 mcg/ml
DI: CYP2C19 substrate; CYP2C9, 2D6, 3A3/4 inhibitor, highly protein bound

Question 13

Lorazepam important info

Answer 13

Brand: Ativan
MOA: increase GABA-ergic inhibition
AEs: *sedation, *ataxia, confusion
t1/2: 10-13 hours (shortest of benzos)

Question 14

Fosphenytoin important info

Answer 14

Brand: Cerebyx
MOA:Na channel
AEs: *nystagmus, *dizziness, *ataxia, ECG or blood changes lower than phenytoin
t1/2: have to wait 2-4 hours to make sure it’s converted to phenytoin

Question 15

What will cause total serum concentrations of a certain AED drug to increase?

Answer 15

If you remove: absorption interference, inducer, or displacer
OR if you add inhibitor

Question 16

What will cause total serum concentrations of a certain AED drug to decrease

Answer 16

IF you add: absorption interference, inducer, or displacer

OR if you remove inhibitor

Question 17

Common Inducers (Most common)

Answer 17

Carbamazepine, Phenytoin, Phenobarbital

Question 18

Common inhibitors (Most common)

Answer 18

Valproic Acid

Macrolides

Question 19

How and when should you monitor if pt is within TR

Answer 19

Measure trough levels in the am after 5 1/2 lives

Question 20

Important info about AEDs and women of childbearing age

Answer 20

PHT, CBZ, PB, and PRM may decrease affect of OC

Avoid VPA during pregnancy (teratorgenic)

Question 21

Criteria to discontinue AEDs

Answer 21

All 5 must be met
sz free for 2-5 years
normal neuro exam
normal IQ
single type of partial or generalized sz
Normal EEG with tx

Question 22

How to tx status epilepticus

Answer 22

ABCs: O2 and IV
Lorazepam: 2-4 mg IV (max 2mg/min)- watch for resp. depression
Also give phenytoin/phosphenytoin at the same time so it can reach TR before Lorazepam before it wears off- must monitor EKG