Epilepsy Flashcards
General mechanism of actions of antiepileptics (AED)?
- Decreased membrane excitability by altering Na+ and Ca2+ conductance during action potential
- Enhance GABA neurotransmitters
Carbamazepine is unsuitable for what type of seizures?
Absence seizures
BZDs can be classified according to their duration of action: Short-acting, intermediate-acting and long-acting. Name an example of each and their usual oral dosage range
- Short-acting: Midazolam 15mg
- Intermediate-acting: Clonazepam 0.5-1mg, Lorazepam 1-2mg
- Long-acting: Diazepam 5mg ++ (should be multiples of 5 bah HAHa)
Definition of epilepsy in terms of the number of seizure episodes?
≥2 unprovoked seizures occurring > 24h apart
Treatment goals for epilepsy
- Absence of seizures
- Absence of AED side effects
- Improve QoL
General principle for dosing AEDs?
Start low titrate slow
According to ILAE 2013, three AEDs that are preferred for Generalised onset epilepsy?
- Lamotrigine (LTG)
- Topiramate (TPM)
- Valproate (VAL)
Which AEDs are preferred in epilepsy with concurrent migraine? State the dosing range of each AEDs
- Topiramate (TPM): 50-200mg in OD-BD titrated weekly, then 100 mg weekly till max 400 mg/day (monotherapy dosing. If adjunct, initial dose is 25 mg)
- Valproate (VAL): 10-15 mg/kg/day in OD-QDS, max 60 mg/kg/day. Increase by 10mg/kg/day weekly
AED that should be used in caution in patients who have concurrent depression or anxiety? State dosing range of the AED.
Levetiracetam (LEV) 500 mg BD, increase by 1000 mg q2w until max 4000mg a day (2000 mg BD)
AEDs that are preferred in women with childbearing potential? State their dosing range
- Levetiracetam (LEV) 500 mg BD, increase by 1000 mg q2w until max 4000mg a day (2000 mg BD)
- Lamotrigine (LTG) 25-500 mg/day
(FYI: This LTG dosing: Generally if nothing interacts with it, initial dose is 25 mg OD. If lamotrigine metabolism is increased by other drugs, then initial dose is 25 mg BD. If lamotrigine metabolism is DECREASED by other drugs, initial dose is 12.5-25mg EOD. This is due to severe cutaneous reaction and is dose dependent)
AEDs that are NOT SUITABLE in pregnancy due to established or possible teratogenicity
Valproate (most established), phenytoin, topiramate, carbamazepine
What is the difference in terms of clearance between first generation AEDs and newer AEDs?
- 1st gen AEDs (CBZ, PHT, VAL) are hepatically cleared
- Newer AEDs (e.g. Gabapentin, LTG, LEV) are mostly renally cleared (except TPM which is 33-50% R cleared)
Newer AEDs that have no effects on CYP enzyme hence less drug interactions?
Gabapentin, levetiracetam and pregabalin
AED that induces its own metabolism. How is it dosed?
Carbamazepine 100-200 mg/day in BD-QDS
(or 2-3mg/kg/day)
AEDs that are potent enzyme INDUCERS
Carbamazepine, Phenytoin
