11.1 - Epilepsy and AEDs Flashcards
what are the 2 types of generalised seizures?
absence and tonic-clonic
What occurs in an absence seizure?
staring, eyelid twitching, few muscle jerks. normal activity post attack
What occurs in a tonic-clonic seizure?
2 phases:
1) Tonic phase - body rigid, patient falls to floor, incontinence
2) clonic phase - convulsions, frothing at mouth, jerking of muscles
Followed by drowsiness, confusion or coma for several hours
What are the 2 types of partial seizures? What occurs in each of them?
Simple - conscious seizure
Complex - impaired consciousness, can become generalised
Define epilepsy
Tendency towards recurrent seizures
Define status epilepticus
Single convulsion lasting >30mins or convulsions ocurring back to back with no recovery
How can status epilepticus cause damage?
Physical injury due to fall, hypoxia, SUDEP
How can epilepsy be classified?
Primary - idiopathic
Secondary - known cause
What are some underlying causes which can result in epilepsy?
Brain tumours, pyrexia, alcohol or drugs or withdrawal, brain tumours, hypoglycaemia, brain injury
How would you take a history of a seizure?
Witness statements, pre, peri, and post seizure
What are the 4 types of AEDs?
Inhibition of glutamate release, inhibition of Ca channel, Inhibtion of Na channel, enhancement of GABA(A) action
What are the 3 types of inhibitiors of na channels?>
Lamotrigine, phenytoin, carbamezepine
What is the MoA of inhibitors of Na channels?
Only binds to channels in inactive state, preventing channels from returning to a resting state where they could continue to depolarise neurons. Preferentially binds high frequency discharge neurons
What are some ADRs of carbamezepine?
N&V, rashes, myelosuppression, dizziness, parasthesia, teratogenic
What are some ADRs of phenytoin?
Gingival hyperplasia, heaches, nystagmus, dizziness, hypersensitivity rashes, teratogenic
What are some ADRs of lamotrigine?
dizziness, ataxia, nausea, rashes,
What are the DDIs of the inhibitors of Na channels?
Phenytoin and carbamezepine - inducers of CYP450
Lamotrigine - oral contraceptives
What are the 2 types of enhancers of GABA action?
Valproate sodium, BZDs
Why is phenytoin used in emergency treatment?
Zero order kinetics - quickly reaches therapeutic levels
What is the MoA of valproate sodium?
Stimulates GABA synthesis and inhibits GABA inactivation
What is the MoA of BZDs
Positive allosteric modulation of GABARs.
Give an example BZD
lorazepam
What are some ADRs of valproate sodium?
ataxia, tremor, N&V, sedation, teratogenic
What are some ADRs of BZDs?
sedation, tolerance, confusion, aggresssion, resp and CNS depression, teratogenic
How would you prescribe an AED? What rules would you folow
aim for monotherapy, start low and increase dose to maximise effect and minimse ADRs
What AED would you use for primary generalised seizures?
Valproate sodium or lamotrogine
What AED would you use for partial seizures?
Carbamezepine or lamotrigine
What AED would you use for Status epilepticus?
BZD and IV phenytoin
What AED would you use in pregnancy and why? What other supplements would you combine it with?
Use lamotrigine - reduced teratogenic effects
Combined with folate and vit K supplements. Vit K reduces risk of cerebral hemorrhage and coagulopathy associated with AED-linked vit K deficiency. Folate reduces risk of neural tube defects
What would you do in an emergency involving status epilepticus?
1) ABC
2) lorazepam and then IV phenytoin
3) treat underlying cause
4) if all else fails, ITU referral with paralysis, sedation and intubation
Give some secondary causes of epilepsy
alcohol, drugs, withdrawal, flashing lights, pyrexia, brain tumours
