Chapter 4 - Epilepsy Flashcards
What are the two main categories of seizures?
Focal (partial) seizures
Generalised seizures
What types of seizures do ‘generalised’ seizured encompass?
Tonic-clonic Tonic Atonic Myoclonic Absence
When initiating anti-epileptic treatment, what method should be taken to reduce the risk of adverse effects?
Titration - should start of low and then titrate upwards until seizure control is met
If an anti-epileptic needs to be stopped or switched, how best should this occur?
Slowly titrating down and/or if initiating new anti-epileptic drug, this should also be titrated upwards slowly until seizure control has been met.
Which two neurotransmitters are generally most commonly associated with excess excitation/ decreased inhibition of excited neuronal activity in the brain, causing seizures to occur?
Glutamate - excitory neurotransmitter
GABA - inibitory neurotransmitter
In epilepsy, there is an increase in glutamate action, causing consistent action potentials to be fired amongst neurones. GABA helps to inhibit this action.
Anti-epileptics can be broadly categorised into 3 modes of action. What are these 3 categories?
1) Modulation of voltage-gated ion channels (target Na+ and Ca2+ channels)
2) Enhanced activity of synaptic inhibition (increased GABA activity)
3) Inhibition of synaptic excitement (decreased glutamate activity)
Sodium valproate can be used for the treatment of which types of seizures?
All types
Carbamazepine, Phenytoin, Lamtrogine are examples of anti-epileptics which have what MOA?
Act on voltage gated Na+ channels, to inhibit influx of Na+ ions into the pre-synaptic neurone — preventing depolarisation and therefore glutamate being released into the synaptic cleft and causing excitation of post-synaptic neuron
Lamotrigine and ethosuximide are examples of anti-epileptics which have what MOA?
Act on voltage gated Ca2+ channels, to inhibit influx of Ca2+ ions into the pre-synaptic neurone — preventing depolarisation and therefore glutamate being released into the synaptic cleft and causing excitation of post-synaptic neuron
How do benzodiazepines work to help control seizures?
Helps to potentiate the effects of GABA on GABA-A receptors — this consequently leads to an influx of Cl- ions into the post-synaptic neuron, causing replorarisation and therefore inhibition of excess excitation of neurons
Which anti epileptic medicines need to be brand specific and patients are to be maintained on that specific brand?
Category 1:
Phenytoin
Carbamazepine
Phenobarbital
Primidone
Which antiepileptic is associated with the highest teratogenic risk?
Sodium Valproate - highest risk of major and minor congenital malformations (in particular neural tube defects) and long term development disorders
To reduce the risk of neural tube defects in renal patients with epilepsy who want to or are pregnant, what is advised to be prescribed?
Folic acid 5mg
What is first line treatment for patients newly diagnosed with focal (partial) seizures?
Carbamazepine or lamotrigine ( lamotrigine is preferred)
What is first line treatment for generalised tonic-clinic seizures?
Sodium valproate or lamotrigine
What is first line treatment for absence seizures?
Ethosuximide or sodium valproate
GABA analogues (Gabapentin and Pregabalin) may be used for what types of seizures? What other indication can they be used for?
Focal seizures
May also be used for neuropathic pain
What else is carbamazepine licensed to be used for aside from epilepsy?
Trigeminal neuralgia
Which type of seizure can lamotrigine exacerbate?
Myoclonic
When initiating treatment with carbamazepine, eslicarbazepine, fosphenytoin or phenytoin, ethinicity plays an important part. Why?
In people of Han Chinese or Thai origin risk of drug induced Stevens-Johnson syndrome if the HLA-B*1502 allele is present
SCREENING for this allele in people of this origin is crucial if no other alternative therapy is available
What serious side effects have been commonly reported or patients/ carers should be advised to look out for with carbamazepine, lamotrigine, oxcarbazepine and phenytoin?
Blood disorders
Patients should be reminded to report any signs of unexplained bleeding, bruising or signs of infection such as sore throat, malaise, fever etc
What is the optimum plasma phenytoin concentration range?
10-20mg/L
What monitoring requirements are needed for sodium valproate?
LFTs - hepatotoxicity has occurred with valproate use, especially in children under the age of 3
If hepatic dysfunction occurs treatment with sodium valproate should be stopped
What specific side effects have been associated with topiramate use?
Acute myopia with secondary angle-closure glaucoma
