Pharm: Antiepileptic Drugz

Question 1

Where do AED limit excitability

Answer 1

• Voltage gated Na channel
• Voltage gated Ca channel
• Glutamate receptors

Question 2

Where do AED enhance inhibition

Answer 2

GABA system

Question 3

Voltage gated Na channel

Answer 3

• Membrane ion channel involved in AP generation
• AED stabilize the inactive state, inhibiting recurrent depolarization
• Ex: Phenytoin,Carbamazepine, Oxcarbamazepine, Lamotrigine. Secondary: Valproate, Felbamate, Topiramate

Question 4

Voltage gated Ca chanel

Answer 4

• Presynaptic membrane channels
• Blocking influx of Ca leads to less excitatory NT release
• Useful in treating neuropathic pain
• Ethosuximide - T-type in thalamus
• Gabapentin, Pregabalin - high voltage types
• Secondary: Topiramate, Felbamate, Phenobarbitol, Lamotrigine, Levitiracetam

Question 5

Glutamate receptors

Answer 5

• Post synaptic membrane of excitatory synapses
• Ligand-gated cation channels (Ca, Na)
• Felbamate - NMDA receptor blocker
• Topiramate - partially active as AMPA and kainate receptor blocker

Question 6

GABA system

Answer 6

• GABA-A receptors found on post synaptic membranes of inhibitory synapses
• Ligand gated Cl channels
• Ex. phenobarbitol, benzos. Secondary: valproate, topiramate, gabapentin, leviteracetam, felbamate

Question 7

Voltage gated sodium channels

Answer 7

• Stabilize inactive state inhibiting recurrent depolarization
• Similar efficacy, metabolism, toxicities
• Hepatic enzyme inducers
• Phenytoin, Carbamazepine, oxcarbamazepine, Lamotrigine