Anti-Epileptic Drugs

Question 0

Describe the MoA of sodium channel blockers

Answer 0

• Binds to internal face of sodium channels in its inactivated state
• Prevents depolarisation of neurone, preventing action potential generation.

Question 1

What are the four classes of AEDs?

Answer 1

• Enhancement of GABA mediated inhibition
• Voltage-gated sodium channel blockers
• Calcium channel blockers
• Inhibition of glutamate release

Question 2

Name three types of VGSC blockers

Answer 2

• Carbamazepine
• Phenytoin
• Lamotrigene

Question 3

Describe the properties of carbamazepine.

Answer 3

• Linear PK
• CYP450 inducer
• Half-life decreases from 30 to 15hrs with repeated use
• Used to treat generalised tonic-clinic seizures and partial seizures

Question 4

List some ADRs of carbamazepine

Answer 4

• Drowsiness, dizziness, ataxia, motor disturbances, paresthesia, anaesthesia
• Nausea and vomitting
• Variations in BP
• Rashes, bone marrow suppression

Question 5

List some DDIs of carbamazepine

Answer 5

• Reduces levels of warfarin, phenytoin, corticosteroids, OCP

Question 6

Describe the properties of phenytoin

Answer 6

• Well absorbed, 90% bound to plasma proteins
• Linear PK at sub-therapeutic levels, non-linear PK at therapeutic levels
• Variable half life (6-24hr) must be monitored
• CYP450 inducer
• Used to treat generalised tonic-clonic and partial seizures

Question 7

List some ADRs of phenytoin

Answer 7

• Dizziness, ataxia, headaches, nystagmus
• Gingival hyperplasia
• Hypersensitivity reactions (Stevens Johnson syndrome)

Question 8

List some DDIs of phenytoin

Answer 8

• Plasma levels are increased if taken alongside valproate due to competitive binding
• Reduces level of OCP
• Increases level of cimetidine

Question 9

Describe the properties of Lamotrigine

Answer 9

• Well absorbed
• Linear PK
• Half life 24 hrs
• Fewer DDIs and ADL
• Used to treat generalised tonic-clonic, partial, and absent seizures
• Unable to cross the placental barrier

Question 10

List some ADRs of Lamotrigine

Answer 10

• Dizziness, ataxia, and somnolence
• Nausea
• Skin rashes

Question 11

List some DDIs of Lamotrigine

Answer 11

• Adjunct therapy with other AEDs
• Plasma levels are reduced by OCP
• Plasma levels are increased by valproate due to competitive binding