Epilepsy and AED's

Question 1

Examples of classical AEDs

Answer 1

phenytoin, phenobarbital, primidone, carbamazepine, ethosuximide, valproate

Question 2

Adverse effects of AEDs

Answer 2

• nause, irritability, headache
• sedation, weight changes
• cosmetic - gum hypertrophy, acne, hurtuism (phenytoin)
• teratogen - sodium valproate
• congiive, behavioural and antiepileptic hypersensitivity syndrome

Question 3

Targets for AEDs

Answer 3

• increase GABA (inhibitory NT)
• decrease glutamate (excitatory NT)
• block voltage gated inward positive currents (Na or Ca)

Question 4

Modulation of GABA receptor (AED)

Answer 4

• reduce GABA metabolism (vigabatrin, valproate)
• reduce GABA reuptake (tiogabine)
• increase GABAa receptor Cl- flux
  
  • benzodiazepine (enhance GABA binding)
  • barbituates - keep channel open longer

Question 5

Reducing Na influx (AED)

Answer 5

-prolongued Na channel inactivation - drugs bind to inactivated form of channel - channel remains open but inactivation gate blocks ion flux

Question 6

Drug interactions (AEDs)

Answer 6

• Phenytoin, carbamazepine, phenobarbital and primidone are autoinducers of cytochrome p450 enzymes (increase its metabollic activity) - e.g. can’t use the pill as oestrogen broken down
• valproate inhibits cytochrome p450 enzymes

Question 7

Status epilepticus

Answer 7

prolongued seizure or cluster of seizures without return to baseline lasting >30 mins - medical emergency

Question 8

Treatment of status epilepticus

Answer 8

1. ABC and seek help
2. Correct any hypoglycaemia
3. Consider parental thiamine if alcohol abuse is suspected
4. Benzodiazepine: 2-4mg lorazepine IV
5. long acting IV AED

Question 9

Alternative uses of AEDs

Answer 9

• neuropathic pain - gabapentin/pregablin/carbamazepine
• bipolar - carbamazepine/lamotrigine
• main - valproic acid
• migraine - topiramate, gabapentin