Antiepileptics

Question 1

What is epilepsy?

Answer 1

Neurological disorder characterised by seizures (uncontrollable firing of neurons)

Question 2

What are the common causes of epilepsy?

Answer 2

• Brain Injury
• Chemical imbalance
• Idiopathic causes

Question 3

What is the effect of antiepileptics on neurons?

Answer 3

Effects firing of action potentials

Question 4

What are the three main mechanisms of antiepileptics?

Answer 4

• Enhancing GABA action
• Inhibition of sodium channel function
• Inhibition of calcium channel function

(Some act by more than one)

Question 5

What is GABA?

Answer 5

The main inhibitory neurotransmitter in the brain

Question 6

What does action of GABA cause?

Answer 6

GABA acts on the GABAA receptor on inhibitory synapses, binding causes Cl- to flow into cell and K+ out of the cell, causing hyperpolarisation, so further action potentials cannot be generated until membrane returns to resting state

Question 7

What are the 3 ways of enhancing GABA action and what drugs work in these ways ?

Answer 7

• Inhibiting GABA transaminase (Vigabatrin, Valproic acid)
• Inhibition of GABA uptake (Tiagabine)
• Potentiating GABA function, GABAa receptor agonists (Topiramate, Benzodiazepines, Barbiturates)

Question 8

Why does the inhibition of sodium channels treat epilepsy?

Answer 8

Sodium channels are important in generating action potentials, blocking these channels would block the excitation of neurons that are firing repetitively, depolarisation increases proportion in inactive state

Question 9

What drugs act by the inhibition of sodium channels?

Answer 9

Carbamazepine, Oxcarbazepine, Phenytoin, Lamotrigine, Valproic acid

Question 10

Why does the inhibition of calcium channels treat epilepsy?

Answer 10

T-Type calcium channels are important in generating rhythmic discharge associated with absence seizures
(Other types are also targets)

Question 11

What are examples of drugs that inhibit calcium channels?

Answer 11

• Ethosuximide and valproate (T type)
• Gabapentin (P/Q type)
• Zonisamide, Pregabalin

Question 12

What are the four other mechanisms of action and what drugs can work this way?

Answer 12

• Blocking AMPA receptors (Topiramate)
• Blocking NMDA receptors (Felbamate)
• Carbonic anhydrase inhibitors (Topiramate)
• Synaptic vesicle targeting (Levetiracetam, Brivaracetam)

Question 13

What other conditions are antiepileptics effective in?

Answer 13

• Bipolar disorder (Valproate, carbamazepine, Topiramate)
• Migraine prophylaxis (Valproate, gabapentin, Topiramate)
• Anxiety disorders (gabapentin)