Specific AEDs

Question 1

CBZ and Phenytoin

Answer 1

• dec Na+ channels (frequency and voltage dependent blockade of Na+ channels; bind channel causing it to remain in inactivated state)
• CP450 inducer…
  - Inc metabolism of oral contraceptives so inc pregnancy
  - Dec Warfarin conc so inc DVT/emboli
  - Inc statin clearance so inc cholesterol
  - Dec TCA conc so inc depression
  • Absorption in gut decreases if on antacids

-ONLY used for partial or tonic-clonic seizures

**Phenytoin is non-linear

Question 2

Lamotrigine

Answer 2

• dec Na+ channels; dec Ca++ channels

- Lamotrigine conc dec if on oral contraceptives so breakthrough seizures

Question 3

TPX

Answer 3

Topirimate

dec Na+ channels, dec excitatory transmission, inc GABA transmission

Question 4

Zonisamide

Answer 4

-dec Na+ channels

Question 5

Valproic Acid

Answer 5

• dec Na+ channels, dec excitatory transmission, inc GABA transmission, dec Ca++ channels
• CP450 enzyme inhibitor

Question 6

Vigabatrin

Answer 6

inc GABA transmission (irreversibly binds and incapacitates GABA transaminase - main enzyme for GABA degradation)

• Unchanged in urine
• Only used for partial or tonic-clonic seizures

Question 7

Tiagabine

Answer 7

inc GABA transmission (inhibits re-uptake of synaptic GABA)

-ONLY used for partial or tonic-clonic seizures

Question 8

Benzodiazepine

Answer 8

inc GABA transmission (enhance effect of GABA of GABA A receptors)