Antiepileptics

Question 1

Phenytoin

Answer 1

MOA: Blocks Na+ channels

Use: partial seizure, tonic-conic seizure; prophylaxis for status epilepticus

Toxicity: hirsutism, coarsening of facial features; peripheral neuropathy, gingival hyperplasia, osteomalacia; Teratogenic (cleft palate)

PK: bound to plasma proteins, induces hepatic cyp450, dose-dependent elimination

Question 2

Valproate

Answer 2

MOA: blocks Na+ channels and NMDA receptors

Use: all seizures (first line for tonic-clonic, myoclonic, and atonic)

SE: hepatitis, weight gain, hair loss, N/V/D

PK: bound to plasma proteins, dose-dependent elimination

Question 3

Carbamazepine

Answer 3

MOA: Blocks Na+ channels

Use: myoclonic and atonic seizure, partial seizure

SE: ADH-like effect may cause water intoxication

PK: induces the hepatic enzyme that facilitates its own metabolism so half-life of subsequent dose is reduced to ~20hrs

Question 4

Ethosuximide

Answer 4

MOA: blocks T-type Ca2+ channels

Use: absence seizure

Question 5

Lorazepam

Answer 5

MOA: Benzodiazepine (increases frequency of channel opening)

Use: status epilepticus

Question 6

Diazepam

Answer 6

MOA: Benzodiazepine (increases frequency of channel opening)

Use: status epilepticus

Question 7

Phenobarbital

Answer 7

MOA: Barbiturate (increases duration of time channel stays open)

Use: second line for partial seizure and tonic-clonic seizures

CI: porphyria

Question 8

Primidone

Answer 8

MOA: biotransformed to phenobarbital and PEMA

Use: second line for partial seizure and tonic-clonic seizures

CI: porphyria

Question 9

Clonazepam

Answer 9

MOA: benzo derivative

Use: myotonic and atonic seizures

Question 10

Lamotrigine

Answer 10

MOA: blocks Na+ channels

Use: all seizures (except status epilepticus)

Question 11

Topiramate

Answer 11

MOA: unknown (Na, GABA?)

Use: partial seizure

SE: kidney stones, decreased appetite

Question 12

Gabapentin

Answer 12

MOA: increases GABA concentration

Use: partial seizure, peripheral neuropathy