Antiepileptics

Question 1

What is a seizure

Answer 1

A paroxysmal event due to abnormal, hypersynchronous discharge from a mass of CNS neurons

Question 2

Risk factors for seizure

Answer 2

Alcohol, hypoglycemia, pyrexia, sleep deprivation

Question 3

Epilepsy

Answer 3

Chronic prolonged risk of seizure

Question 4

Determinations of high risk of recurrent seizures

Answer 4

Previous seizures, epileptiform EEG, abnormal brain scan

Question 5

Diagnosis of epilepsy is based on

Answer 5

Clinical history and examination

Appropriate investigations to determine risk of recurrent seizures (blood tests, EEG, brain scan)

Question 6

Pathophysiology of epilepsy

Answer 6

Excessive synchronous depolarisation, due to unbalanced excitatory and inhibitory receptor/ion channel function which favour depolarisation → dysregulated discharge

Question 7

Causes of epilepsy

Answer 7

Congenital or hereditary 
Brain injury, scarring or tumour
Infections: meningitis or encephalitis 
Blood glucose alterations
Metabolic disorders eg adrenal insufficiency

Question 8

Types of generalised seizures

Answer 8

Tonic clonic, absence, myoclonic, atonic

Question 9

WHich seizures lead to loss of consciousness

Answer 9

tonic clonic, absence, myoclonic, atonic, complex partial seizures

Question 10

MOA of antiepileptics

Answer 10

Decrease membrane excitability by altering Na+ and Ca2+ conductance during action potentials
Enhance effects of inhibitory GABA neurotransmitters

Question 11

Phenytoin MOA

Answer 11

Blockade of voltage-dependent Na+ channels

Question 12

Which seizures are phenytoin and carbamazepine suitable for?

Answer 12

All seizures except absence seizures

Question 13

Who should avoid phenytoin?

Answer 13

Pregnant women and women of child-bearing age

Question 14

Phenytoin kinetics

Answer 14

Saturable kinetics and non-linear relationship

Question 15

Carbamazepine MOA

Answer 15

Blockade of voltage-dependent Na+ channels

Question 16

How is carbamazepine cleared?

Answer 16

CYP450 metabolism

Question 17

Carbamazepine AE

Answer 17

Aplastic anemia

Question 18

Valproate MOA

Answer 18

Blockade of voltage dependent Na+ and Ca2+ channels

Inhibits GABA transaminase (breaks down GABA → so GABA increases)

Question 19

AEs of antiepileptics

Answer 19

Dose related: drowsiness, mental changes, coma

Non-dose related: folate deficiency, osteomalacia, gingival hyperplasia, acne, hypersensitivity, hirshutism

Question 20

Benzodiazepines MOA

Answer 20

Enhance effects of inhibitory GABA neurotransmitters

Question 21

When will benzodiazepine be first line

Answer 21

Status epilepticus → diazepam, lorazepam, clonazepam

Question 22

Monitoring of antiepileptic drug levels

Answer 22

Assessment of compliance in patients with refractory epilepsy
Assessment of symptoms due to possible antiepileptic drug toxicity
titration of phenytoin dose