L3 Antiepileptics

Question 1

Accurate diagnosis of epilepsy from:

Answer 1

clinical history and examination: determine risk of recurrent seizures
- Do not rush to diagnose based on blood tests (LFT, blood chemistry), EEG, brain scan (MRI/CT)

Question 2

Pathophysiology of epilepsy

Answer 2

Unbalanced excitatory and inhibitory receptor/ion channel function, favouring depolarisation, resulting in dysregulated discharge

Question 3

Grand mal

Answer 3

Tonic clonic

Question 4

Petit mal

Answer 4

Absence generalised seizure

Question 5

What type of seizures can phenytoin be used for?

Answer 5

Suitable for all types of seizures except absence seizures

Question 6

Can phenytoin be used for pregnancy?

Answer 6

No! Teratogenic: toxic for developing fetus, causes mutation

Question 7

Important thing to note for phenytoin

Answer 7

Titration and monitoring is necessary:

• relatively narrow therapeutic range (plasma conc 40-100uM)
• saturation kinetics, consequent non-linear rs between dose and plasma conc

Question 8

Which antiepileptic drug has the exact same MOA as phenytoin? Are they structural analogues?

Answer 8

Carbamazepine, different chemical structure

Question 9

What type of seizures can carbamazepines be used for?

Answer 9

Suitable for all types of seizures except absence seizures

Question 10

What is a dangerous ADR of carbamazepine?

Answer 10

rare but very dangerous: asplastic anemia (bone marrow not producing blood cells anym, 2 per million per year)

Question 11

Important thing to note for carbamazepine

Answer 11

Induces its own metabolism: CYP450 inducer, t1/2 shortens with repeated doses

Question 12

How does valporate’s MOA differ from that of phenytoin and carbamazepine?

Answer 12

Valporate also blocks voltage-dependent Ca2+ channels and inhibits GABA transaminase (leading to increase GABA, hence incr inhibitory tone)

Question 13

What type of seizures can valporate be used for?

Answer 13

Suitable for all types of seizures

Question 14

Important thing to note for valproate

Answer 14

strongly bound to plasma proteins, displaces other antiepileptics

Question 15

Important thing to note for benzodiazepines

Answer 15

Also anxiolytics, hence can be potentially addictive, leading to dependence
- but work faster (used in emergency situations)

Question 16

What are 2 examples of an intermediate-acting antiepileptic?

Answer 16

Clonazepam (Klonipin): panic disorder, seizure

Lorazepam (Ativan): anxiety, insomnia, status epilepticus

Question 17

What is 1 example of an long-acting antiepileptic?

Answer 17

Diazepam (Valium): alcohol withdrawal syndrome, anxiety, sedation, status epilepticus, seizure, refractory seizure, adjunct skeletal muscle spasm

Question 18

What are benzodiazepines usually used for (in epilepsy treatment)?

Answer 18

Adjuvant/emergency situations

Question 19

Patient should commence on mono/multi-therapy initially?

Answer 19

mono!

Question 20

Should the patient develop an adverse reaction to the initial drug or if the initial monotherapy is unsuccessful,

Answer 20

MONOTHERAOY using another drug should be tried - do not add on!

Question 21

Which antiepileptic drug has the highest efficacy?

Answer 21

All antiepileptic drugs licensed for monotherapy ie. carbamazepine, phenytoin, sodium valproate - have similar efficacy in newly diagnosed epilepsy

• Prescribing physicians use the medicine that they are most familiar with
• First line treatments for newly diagnosed particial and generalised tonic clinic seizures

Question 22

Routine checking of antiepileptic drug levels without a clear clinical indication is not required, and is not cost-effective - what are the indications for antiepileptic drug levels testing?

Answer 22

1. assessment of compliance for pt treated for refractory epilepsy
2. assessment of smx due to possible drug toxicity
3. phenytoin dose titration