Antiepileptic Drugs

Question 1

What are the 4 Na+ channel stabilizers used for epilepsy? Which ones are used for primary generalized? complex partial?

Answer 1

Phenytoin (Dilantin) [acute seizures, primary generalized]
Carbamazepine [complex partial]
Oxcarbamazepine [complex partial]
Lamotrigine [primary generalized

Question 2

Besides epilepsy, what are 2 other uses of carbamazepine and other in its class?

Answer 2

Stabilize inactive conformation of Na channel–>

bipolar disorder and neuropathic pain

Question 3

What are 2 side effects of Lamotrigine and the others in its class?

Answer 3

rash (15%); contraceptive failure due to enzyme induction

Question 4

What are 2 side effects specific to carbamazepine and oxcarbamazepine? What is the difference between the 2 drugs?

Answer 4

• mild myelosuppression, mild increase in LFTs
• oxcarbamazepine Designed to bypass carbamazepine epoxide; less protein-bound, less autoinduction, fewer interactions, less toxic, longer half-life than carbamazepine

Question 5

Which Na+ channel blocker is a hepatic enzyme inducer (both auto- and hetero-inducer); highly protein bound; must increase dose in 1-2 wks due to autoinduction?

Answer 5

Carbamazepine

Question 6

Which Na+ channel blocker competes with Valproic acid for excretion?

Answer 6

Lamotrigine

Question 7

What are the toxicity side effects of Phenytoin and the others in its class?

Answer 7

Na+ channel blocker–>

“dizzy, drunk, double vision”

Question 8

Which epileptic agent is teratogenic?

Answer 8

Valproate

Question 9

What are 4 uses of Valproate?

Answer 9

1. seizures (primary generalized & partial)
2. bipolar
3. migraine prophylaxis
4. IV infusion for status epilepticus

Question 10

What are some side effects of Valproate?

Answer 10

Weight gain, hair turnover, hyperammonemia (which can be mitigated with oral carnitine), teratogenicity, blood dyscrasias; pancreatitis

Question 11

What are benzodiazepines role in epilepsy?

Answer 11

Status epilepticus (refractory); anesthesia
SE: sedation
Long-term usefulness limited by tolerance

Question 12

What is the class, mechanism and use of Gabapentin?

Answer 12

GABA analog–>
Block presynaptic influx of Ca++ –>
Adjunct for partial complex epilepsy; more commonly used for neuropathic pain

Question 13

Which agent is not metabolized in humans? (eat and pee unchanged)?

Answer 13

Gabapentin

Question 14

What is a voltage-gated Ca++ channel blocker used to treat absense seizures? Side effects?

Answer 14

Ethosuximide–>

Side effects: Nausea (transient), sedation, irritability

Question 15

What are 2 glutamate receptor blockers? Which receptors do they work at? Used to treat?

Answer 15

Topiramate (AMPA)
Felbamate (NMDA)
treat partial onset seizures [topiramate also headaches]

Question 16

What are some side effects of Topiramate?

Answer 16

[Ca++ channel blocker]
Toxicity: sedation, “word finding”
SE: mild metabolic acidosis –> tingling, distaste for carbonated beverages, kidney stones, rare acute glaucoma

Question 17

What is an uncommon but serious side effect of Felbamate?

Answer 17

Uncommon but potentially fatal. Aplastic anemia, acute hepatic failure. Requires monitoring. (not used much anymore)