anti-convulsants

Question 1

define seizure

Answer 1

sudden changes in behaviour caused by electrical hypersynchronisation of neuronal networks in cerebral cortex

Question 2

how can brain activity be measured?

Answer 2

• EEG

- MRI

Question 3

what are general seizures and the types?

Answer 3

• 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

Question 4

describe what happens in tonic-clonic seizures

Answer 4

• loss of consciousness
• muscle stiffening
• jerking/ twitching
• deep sleep
• wakes up

Question 5

what are partial/ focal seizues and what are the types?

Answer 5

• begins within particular area, may spread out
• simple: retained awareness/ consciousness
• complex: impaired awareness/ consciousness

Question 6

describe the steps to neurotransmission at glutamatergic synpase

Answer 6

1. VGSC opens –> membrane depolarisation
2. VGKC opens –> membrane repolarisation
3. Ca influx through VGCCs –> vesicle exocytosis
4. synaptic vesicle associated protein (SV2A) allows vesicle attachment to presynaptic membrane
5. glutamate activated excitatory post-synaptic receptors (e.g. NMDA, AMPA)

Question 7

name 2 VGSC blockers

Answer 7

• Carbamazepine

- Lamotrigine

Question 8

what does Carbamazepine do?

Answer 8

• stabilizes inactive state of Na channel

- reduces neuronal activity

Question 9

what does Lamotrigine do?

Answer 9

• inactivates Na channels

- reduces glutamate neuronal activity

Question 10

what are the pharmacokinetics of carbamazepine?

Answer 10

• enzyme inducer
• onset of activity within 1 hour
• 16-30 hour half life

Question 11

what are the indications for use of carbamazepine?

Answer 11

• tonic-clonic

- partial

Question 12

what are the pharmacokinetics of lamotrigine?

Answer 12

• onset of activity within 1 hour

- 24-34 hour half life

Question 13

what are the indications for use of lamotrigine?

Answer 13

• tonic clonic

- absence

Question 14

name a VGCC blocker and how it works

Answer 14

• Ethosuzimide
• T-type Ca channel antagonist
• reduces activity in relay thalamic neurones

Question 15

what is the pharmacokinetics and indications of ethosuximide?

Answer 15

• long half life = 50 hours

- used in absence seizures

Question 16

what is levetiracetam and when is it indicated?

Answer 16

• binds to synaptic vesicle associated protein
• prevents glutamate release
• used in myoclonic seizures

Question 17

what is topiramate and when is it indicated?

Answer 17

• inhibits NDMA and kainite receptors
• also affects VGSCs and GABA receptors
• used in myoclonic seizures

Question 18

describe what happens in GABAergic synapses?

Answer 18

• 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

Question 19

describe diazepam and when is it indicated

Answer 19

• GABA receptor, PAM –> inc. GABA-mediated inhibition
• rectal gel = fast onset
• indicated for status epilepticus

Question 20

what is the MoA of sodium valproate and indications for use?

Answer 20

• inhibits GABA-T
• inc. GABA mediated inhibition
• fast onset = 12 hour half life
• indicated for all forms of epilepsy