anti-convulsants Flashcards
define seizure
sudden changes in behaviour caused by electrical hypersynchronisation of neuronal networks in cerebral cortex
how can brain activity be measured?
- EEG
- MRI
what are general seizures and the types?
- begins simultaneously in both hemispheres of brain
1. tonic clonic: loss of consciousness
2. absence: brief staring episodes with behavioural arrest
3. tonic: sudden muscle stiffening/ sudden loss of muscle control
4. myoclonic: sudden, brief muscle contractions
5. status epilepticus: > 5 min of continuous seizure activity
describe what happens in tonic-clonic seizures
- loss of consciousness
- muscle stiffening
- jerking/ twitching
- deep sleep
- wakes up
what are partial/ focal seizues and what are the types?
- begins within particular area, may spread out
- simple: retained awareness/ consciousness
- complex: impaired awareness/ consciousness
describe the steps to neurotransmission at glutamatergic synpase
- VGSC opens –> membrane depolarisation
- VGKC opens –> membrane repolarisation
- Ca influx through VGCCs –> vesicle exocytosis
- synaptic vesicle associated protein (SV2A) allows vesicle attachment to presynaptic membrane
- glutamate activated excitatory post-synaptic receptors (e.g. NMDA, AMPA)
name 2 VGSC blockers
- Carbamazepine
- Lamotrigine
what does Carbamazepine do?
- stabilizes inactive state of Na channel
- reduces neuronal activity
what does Lamotrigine do?
- inactivates Na channels
- reduces glutamate neuronal activity
what are the pharmacokinetics of carbamazepine?
- enzyme inducer
- onset of activity within 1 hour
- 16-30 hour half life
what are the indications for use of carbamazepine?
- tonic-clonic
- partial
what are the pharmacokinetics of lamotrigine?
- onset of activity within 1 hour
- 24-34 hour half life
what are the indications for use of lamotrigine?
- tonic clonic
- absence
name a VGCC blocker and how it works
- Ethosuzimide
- T-type Ca channel antagonist
- reduces activity in relay thalamic neurones
what is the pharmacokinetics and indications of ethosuximide?
- long half life = 50 hours
- used in absence seizures
what is levetiracetam and when is it indicated?
- binds to synaptic vesicle associated protein
- prevents glutamate release
- used in myoclonic seizures
what is topiramate and when is it indicated?
- inhibits NDMA and kainite receptors
- also affects VGSCs and GABA receptors
- used in myoclonic seizures
describe what happens in GABAergic synapses?
- GABA can be released tonically and following neuronal stimulation
- GABA activated inhibitory post-synaptic GABAa receptors
- these receptors are Cl channels = membrane hyperpolarisation
- GABA taken up by GAT and metabolised by GABA-T
describe diazepam and when is it indicated
- GABA receptor, PAM –> inc. GABA-mediated inhibition
- rectal gel = fast onset
- indicated for status epilepticus
what is the MoA of sodium valproate and indications for use?
- inhibits GABA-T
- inc. GABA mediated inhibition
- fast onset = 12 hour half life
- indicated for all forms of epilepsy
