Antiepileptic Drugs Flashcards
Define seizure, what do symptoms depend on?
An episode of abnormal synchronized high-frequency electrical activity within the brain. 50-70% is idiopathic (due to a condition/disease)
Seizures are dependent on what part of the brain they affect - motor cortex, reticular formation centre and hippocampus
What is the difference between a seizure and convulsion?
A seizure is to do with abnormal electrical activity in the brain. Convulsions is due to random muscle movements that can’t be controlled.
What are the two types of seizure?
Generalised and Partial
What are the two sub-divisions of generalised seizures?
Tonic-clonic
Where strong contractions of all musculature occurs. Respiration stops. Hoarse cry, defecation & salivation occur. Followed by a series of violent jerks.
Absence - normally in children and are known to grow out of it. Abrupt ceasing of normal activity and stare vacantly. Often mistaken for day-dreaming
What is a partial seizure?
Where the seizure only affects part of the brain. The symptoms are dependent on the region of the brain affected. Normally the loss of consciousness doesn’t occur. Increases with age, so may be due to brain lesions.
What are the three antiepileptic drugs?
What is a requirement when on these drugs?
Sodium channels
t-type calcium channels
GABA Activators
Must be take continuously.
What is the purpose of GABA receptors?
MOA and examples
Benzodiazepines (ie diazepam) are examples of GABA receptors. These enhance the activation of GABAa facilitating their opening.
Vigabatrin - binds irreversibly to GABA transaminase in astrocytes
Tigabine - inhibits the reuptake of GABA
What does Valproic acid do?
Increases GABA production in the nerve terminal
Inhibits sodium channels and inhibits T-type sodium channels
Effective against all seizures & bipolar disorder
What are sodium channel blocking drugs?
Requirements?
Use - dependence?
Phenytoin - Narrow therapeutic index. Rather than blocking the channel they desensitise the channel.
Many show the property of use dependence - drug binds to Na channel in the inactivated state provided it has been previously opened.
Blocking sodium channels prevent action potentials from occurring. Regular blood tests are required.
What are calcium channel blockers designed to treat?
What specific type?
T-type calcium channels. Treat absence seizures
Ethosuximide
What is carbamazepine?
MOA
Derived from?
Drug of choice for tonic-clonic & partial derived from TCA
Affects sodium channels - stabilises inactivated stage voltage gated Na channel.
Can be used for other treatments : sedative, analgesic, anti-depressant (manic depressive illness)
Low adverse drug reactions
What is a downside to carbamazepine?
It induces the action of hepatic microsomal enzymes. This increases not only its drug metabolism but also other drugs metabolism. In tune - a higher dose is required to overcome the enzymes effects
What are drug is drowsiness, dizziness and ataxia associated with?
Carbamazepine
