Anti-epileptic drugs

Question 1

How do voltage gated sodium channels treat epilepsy

Answer 1

Bind to Na channels in depolarised neurones to keep them deactivated
Preferentially bind to focal area of increased depolarisation so prevent spread of neuronal hyperactivity

Question 2

Examples of voltage gated Na channel blockers to treat epilepsy

Answer 2

Carbamazepine
Lamotrigine
Phenytoin

Question 3

Contraindications for carbamazepine

Answer 3

AVN conduction disorders

Question 4

Side effects of carbamazepine

Answer 4

Leukopenia
Diplopia
Blurred vision
Impaired balance
Erythematous rash (mild)

Question 5

Drug interactions of carbamazepine

Answer 5

Decreases concentration of:
Phenytoin
OC pill
Warfarin
Corticosteroid
Antidepressants

Question 6

What categories of epilepsy carbamazepine and phenytoin treat

Answer 6

Tonic clonic

All partial

Question 7

What categories of epilepsy do lamotrigine and valproate treat

Answer 7

All generalised (including absence) 
All partial

Question 8

What kinetic order does phenytoin follow

Answer 8

0 order at therapeutic dose

Question 9

Side effects of phenytoin

Answer 9

Dizziness
Ataxia
Headache
Nystagmus
Gingival hyperplasia (20%)
Stevens johnson syndrome (2-5%)

Question 10

Drug interactions for phenytoin

Answer 10

Decreases concentration of OC pill

Levels are increased in plasma by NSAIDs and cimetidine

Question 11

Side effects of lamotrigine

Answer 11

Maculopapular rashes
Steven Johnson syndrome
Diplopia
Blurred vision
Photosensitivity 
(More side effects in children so not first line for paeds)

Question 12

Drug interactions for lamotrigine

Answer 12

Plasma levels increased by valproate

Plasma levels decreased by OC pill

Question 13

Examples of drugs that increase GABA to treat epilepsy

Answer 13

Valproate

Benzodiazepines

Question 14

Role of GABA in treating epilepsy

Answer 14

Binds to GABA receptor so increased Cl influx which causes hyperpolarisation of neurones

Question 15

MoA of valproate

Answer 15

Inhibits GABA inactivation

Increases GABA synthesis

Question 16

Side effects of valproate

Answer 16

Nausea very common - have with meal
Sedation
Tremor
Weight gain 
Increased LFTs (40%)
Pancreatitis 
Hair loss

Question 17

Drug interactions for valproate

Answer 17

Plasma levels increased by aspirin

Plasma levels decreased by antidepressants and antipsychotics

Question 18

MoA of benzodiazepines for epilepsy

Answer 18

Positive allosteric effector of GABA receptor

Question 19

Side effects of benzodiazepines

Answer 19

Sedation
Tolerance
Dependence/seizure on withdrawel
Confusion
Aggression
Respiratory depression

Question 20

What can reverse a benzodiazepine overdose

Answer 20

IV flumazenil

Question 21

What categories of seizures do benzodiazepines treat

Answer 21

Status ellipticus (lorazepam)
Absence (clonazepam)

Question 22

Treatment for status ellipticus

Answer 22

IV lorazepam
IV phenytoin
Propofol

Question 23

Difficulty with AED prescribing in pregnancy

Answer 23

Risk of seizure = hypoxia

Risk of treatment = birth defects

Question 24

What should be given to pregnant epileptic women

Answer 24

Lamotrigine
Folate supplements
Vitamin K supplements

Question 25

Which antiepileptics are present in breast milk

Answer 25

All except carbamazepine and valproate

Question 26

Principles of drug choice in epilepsy

Answer 26

Monotherapy!
Build up dose over 2-3 months until epilepsy controlled or reach max dose
If ineffective or not tolerated, switch
Only withdraw 1st drug once established on 2nd
If seizure free for over 2 years, can decrease dose over 2-3 months