Antiepileptics

Question 1

What class is Phenytoin

Answer 1

Sodium channel blocker

Question 2

Phenytoin is used for what types of seizures

Answer 2

GTC and partial seizures

Question 3

Side effects of phenytoin

Answer 3

Nause, loss of appetite
Poor coordination, drowsiness
Hirsutism, gums hyperplasia
BM suppression
Osteoporosis
TEN - HLAB 1502
Teratogenic

Question 4

Phenytoin induces which enzyme

Answer 4

3A4 and 2C9

Question 5

What drugs increase phenytoin levels

Answer 5

Warfarin and trimetoprim

Question 6

Describe the metabolism and elimination of phenytoin

Answer 6

Mixed-order kinetics. Upon saturation, small increase in dose may lead to large increase in drug concentration

Question 7

What type of seizures do carbamazepine prevent

Answer 7

GTC and partial seizures
NOT for myoclonic

Question 8

Mechanism of action of carbamazepine

Answer 8

Binds preferentially to inactive form of sodium channel, inhibit entry of sodium and suppress AP

Question 9

Side effects of carbamazepine

Answer 9

NV, constipation
poor coordination, drowsiness
Decreased WBC and platelet
Hyponatremia, SIADH
TEN and SJS - HLAB 1502
Teratogenic

Question 10

Drugs decreasing metabolism of carbamazepine

Answer 10

erythromycin, cimetidine, CCB

Question 11

Carbamazepine is an inducer of…

Answer 11

CYP 450 (increase clearance of many drugs), strong inducer and it’s own plasma half-life is shortened to 15H when given repeatedly

Question 12

Indications of sodium valproate

Answer 12

GTC, partial seizures, absence seizures

Question 13

Side effects of sodium valproate

Answer 13

NV, constipation
poor coordination, drowsiness
hepatotoxicity
decreased platelets, bleeding
pancreatitis
suicidal behaviour
teratogenic

Question 14

Sodium valproate is an inducer or inhibitor?

Answer 14

Inhibitor of 2C9, glucuronyl transferase and epoxide hydrolase + highly protein bound

Question 15

MOA of valproate

Answer 15

Blocks voltage-gated sodium channels, increased brain levels of GABA

Question 16

GABA system enhanced by?

Answer 16

1) binding directly to GABA-A receptors - BZD, barbiturates
2) inhibit reuptake of GABA - tiagabine
3) inhibit metabolism by GABA transaminases - vigabatrine
4) GAD modulator - gabapentin, valproate?

Question 17

What drugs are glutamate blockers

Answer 17

AMPA - topiramate
NMDA - felbamate, levetiracetam

Question 18

How do glutamate blockers work?

Answer 18

Drug binds to glutamate receptors and block it, prevents flow of calcium and sodium ion into cell resulting in inhibition

Question 19

Monotherapy of new AEDs

Answer 19

topiramate, oxcarbazepine and lamotrigine

Question 20

AEDs to use in concomitant migraine

Answer 20

valproate, gabapentin, topiramate

Question 21

AEDs to avoid in young women

Answer 21

Valproate (high teratogenecity)
Phenytoin (cosmetic effects - hirsutism)

Question 22

AEDs that are hepatic enzyme inducers

Answer 22

Phenytoin
Carbamazepine
Barbiturates
Oxcarbazepine
Topiramate

Question 23

First line AEDs choice

Answer 23

carbamazepine, phenytoin, valproate

Question 24

When are AED level tested

Answer 24

AED level help clinical management under following clinica indications:
1) assessment of compliance in refractory epilepsy
2) assessment of symptoms due to AED toxicity
3) titration of phenytoin dose

Question 25

How to assess AED treatment working

Answer 25

1) Seizure frequency - ensure to assess if it is truly a seisure or other ddx (syncope, TIA, hypogly etc..)
2) Assess if there are any risk of breakthrough seizures:
- non compliance to AEDs
- DDI with other medications that lower AED levels
- alcohol abuse
- sleep deprivation
- concurrent illness

Question 26

Risks for breakthrough seizures

Answer 26

Non-compliance to AEDs
Interactions with AEDs that lower AED serum level
Alcohol abuse
Sleep deprivation
Concurrent illness

Question 27

When would you check patients after titrating AEDs?

Answer 27

5 half-life to new steady state so 1 month later