Antiepileptic drugs

Question 1

Carbamazepins

Answer 1

MOA: inhibition of AP by Na channel block (stabilized channel and prevents restin state)

PK: orally, HL = 30h but shorter w/ repeated administration

AE:

• unsteadiness
• sedation
• mental disorientation
• water retention

TU:

• partial seizures
• generalized tonic-clonic seizures

Interacts w/ drugs bc induce P450 liver enzymes

Question 2

Phenytoin

Answer 2

MOA: inhibition of AP by Na channel block

PK: zero-order metabolism -> disproportionate increase in plasma [ ] as dose increase (monitoring of plasma [ ] is necessary)

AE:
Dose
- vertigo
- confusion
-insomnia
- ataxia

Non-dose

• rashes, increase hair
• megaloblastic
• teratogenic
• thick gums

TU:

• partial seizures
• generalized tonic-clonic
• status epilepticus

Interacts w/ drugs bc induce P450 liver enzymes

Question 3

Ethosuximide

Answer 3

MOA: inhibition of AP by T-type Ca block and inhibition of GABA reuptake / metabolism -> enhanced GABA transmission

PK:

• orally
• HL = 15hs
• 90% bound to albumin

AE:

• fewer than others
• GIT disturbances
• teratogenic
• alteration in hair thickness
• liver failure (rare)

TU:

• generalized absence
• generalized tonic-clonic

Question 4

Clonazepam and Diazepam

Answer 4

BZP

MOA: agonists at the BZP site on the GABA-A R -> enhanced GABAergic (GABA-A) transmission

AE: sedation

TU:

• generalized absence
• generalized tonic-clonic
• i.v. for status epilepticus

Question 5

Phenobarbital

Answer 5

BZP

MOA: 2nd line

Question 6

Vigabatrin

Answer 6

New agent

MOA: inhibition of GABA reuptake / metabolism

PK: p.o.

AE: giddiness, sedation, depression, hallucinations

TU: all types and is effective in resistant epilepsy

Question 7

Lamotrigine

Answer 7

New agents

MOA: inhibition of glutamate release -> decrease glutamergic transmission

PK: p.o

AE: giddiness, ataxia, skin rashes, GIT disturbances

TU: all types of epilepsy