Pharmacology of Epilepsy Flashcards
What are the 4 most common main drug classes prescribed for epilepsy / convulsions?
- Lamotrigine
- Sodium valproate
- Diazepam
- Levetiracetam
What is the primary mechanism of action for Lamotrigine?
Blocks voltage gated Na+ channels preventing Na+ influx
Prevents depolarisation of glutamatergic neurones and reduces glutamate excitotoxicity
What is the drug target site for Lamotrigine?
Voltage gated Na+ channels
What are the main side effects for Lamotrigine?
Side effects:
Common: Rash, drowsiness
Less common but serious:
Steven-Johnson’s syndrome, suicidal thoughts
What condition is Lamotrigine particularly useful for?
Introducing lamotrigine gradually is one of the keys to reducing the frequency and severity of allergic skin reactions
What is the primary mechanism of action for Sodium valproate?
Inhibition of GABA transaminase prevents the breakdown of GABA
This increases GABA concentrations directly in the synapse presynaptically and also indirectly prolongs GABA in the synapse due to the fact that extraneuronal metanolism of GABA is slowed which also slows GABA removal from the synapse
What is the drug target site for Sodium valproate?
GABA transaminase
What are the main side effects for Sodium valproate?
Side effects (MANY):
Common: Stomach pain and diarrhoea, drowsiness, weight gain, hair loss
Serious:
hepatotoxicity, teratogenicity, pancreatitis
How can Sodium valproate impact other drugs?
Broad CYP enzyme inhibitor - increases serum concentration of many co-administered drugs
What is the primary mechanism of action for Diazepam?
Increases choride ion influx in response to GABA binding at the GABA A receptor. Increased chloride ion influx associated with hyperpolarisation of excitatory neurones
What is the drug target site for Diazepam?
Benzodiazepine site on the GABA A receptor
What are the main side effects for Diazepam?
Side effects:
Common: Drowsiness, respiratory depression (if i.v. or at high dose)
Uncommon but serious:
Haemolytic anaemia, jaundice
Why is Diazepam not given long term?
Main reason that diazepam is not used for long term suppression of seizures is due to the development of tolerance
Diazepam is a Schedule 4 controlled drug - addiction prone individuals more likely to become dependent on diazepam
What is the primary mechanism of action for Levetiracetam?
Inhibition of the synaptic vesicle protein SV2A. It inhibits this protein and prevents vesicle exocytosis. A reduction in glutamate secretion is reduces glutamate excitotoxicity
What is the drug target site for Levetiracetam?
Synaptic vesicle protein SV2A