Lec 3: Antiepileptic Agents Flashcards
what are the two different cellular mechanisms associated with seizures?
too much excitation (ions flowing inward like Na2+ and Ca2+) via the glutamate NT
too little inhibition (ions flowing outward like Cl- and K+) via the GABA NT
“anti-seizure drugs” can be prescribed for other reasons such as?
migraines (prophylactic) and some pain conditions
define what Epilepsy is
A CHRONIC disorder characterized by recurrent seizures
what is Dravet Syndrome?
a mutation in a Na+ channel subunit SCN1A
T/F the majority of people with epilepsy are resistant to treatments and usually try various treatments before finding one that is beneficial
False, only 30% of people are refractory to treatment
what does SUDEP stand for?
sudden unexplained death in epilepsy
list the first generation antiseizure medications
potassium bromide, phenobarbital, phenytoin, primidone, and ethosuximide
what is phenytoin specifically classified as?
an Na2+ channel blocker
what is primidone specifically classified as?
an Na2+ channel and GABA blocker
what is ethosuximide specifically classified as?
T-type Ca2+ channel blocker
list the second generation antiseizure medications
Benzos:
diazepam, carbamazepine, valproate, clonazepam, and clobazam
T/F benzos have broad anti-seizure activity
True
what is carbamazepine specifically classified as?
Na+ channel blocker
what is valproate specifically classified as?
Na+ channel blocker
what is clonazepam specifically classified as?
GABA potentiation
what is clobazam specifically classified as?
GABA potentiation
Vigabatrin:
drug class?
what does it do?
third generation antiseizure agent
irreversible GABA-T inhibitor
Lamotrigine
drug class?
what does it do?
third generation antiseizure agent
Na+ channel blocker
Oxcarbazepine
drug class?
what does it do?
third generation antiseizure agent
Na+ channel blocker
Felbamate
drug class?
what does it do?
third generation antiseizure agent
multiple functions
Gabapentin
drug class?
what does it do?
third generation antiseizure agent
binds presynaptic calcium channel α2δ subunit to modulate NT (Glutamate) release
Topiramate
drug class?
what does it do?
third generation antiseizure agent
multiple functions
Tiagabine
drug class?
what does it do?
third generation antiseizure agent
GABA potentiation; inhibits GABA reuptake
Levetiracetam (Keppra)
drug class?
what does it do?
third generation antiseizure agent
Synaptic Vesicle Glycoprotein 2A (SV2A) modulation
Zonisamide
drug class?
what does it do?
third generation antiseizure agent
Na+ channel blocker
Pregablin
drug class?
what does it do?
third generation antiseizure agent
presynaptic calcium channel α2δ subunit
Rufinamide
drug class?
what does it do?
third generation antiseizure agent
Na+ channel blocker
Lacosamide (Vimpat)
drug class?
what does it do?
third generation antiseizure agent
enhanced slow activation of sodium channels
Eslicarbazepine acetate
drug class?
what does it do?
third generation antiseizure agent
a prodrug to Eslicarbazepine - Na+channel blocker
Retigabine
drug class?
what does it do?
third generation antiseizure agent
K+ channel activator
Perampanel
drug class?
what does it do?
third generation antiseizure agent
Glutamate (AMPA) antagonist
Brivaracetam
drug class?
what does it do?
third generation antiseizure agent
SV2A modulation
Cannabidiol (CBD)
drug class?
what does it do?
third generation antiseizure agent
CB1 negative allosteric modulator
Cenobamate
drug class?
what does it do?
third generation antiseizure agent
Na+channel enhances inactivation and slows recovery; possible GABA receptor upregulation
Define a class I seizure
partial, focal, local seizures: seizure is confined to a local area
Define a class II seizure
generalized seizures: bilaterally symmetrical and without local onset
Define a class III seizure
unclassified seizures
Define a class IV seizure
special syndromes: syndromes characterized by the presence of seizures
Define a class I “simple partial” seizure
Consciousness is not impaired
Define a class I “complex partial” seizure
Impaired consciousness: begins as a simple partial seizure that progresses and is preceded by an aura. impaired memory occurs during seizure
Define a class I “Partial seizure evolving into secondarily generalized
tonic-clonic seizure”
alternating contractions with relaxation causing loss of consciousness preceded by an aura
Define a class II “absence (petit mal)” seizure
sudden interruption of consciousness, blank stare, no aura
Define a class II “myoclonic” seizure (random discharges in motor cortex)
brief and sudden contractions of muscles
Define a class II “tonic-clonic (grand mal)” seizure
abrupt onset usually with no aura with contractions and relaxation/shaking followed by unconsciousness
define what status epilepticus is
either:
-seizures occurring acutely in greater intensity, number, or length than usual
-prolonged seizure lasting longer than 10 minutes or repeated seizures over the course of 30 minutes
is status epilepticus occurrence a major concern?
yes, it is life threatening and emergency care should begin immediately
how can we treat status epilepticus?
initially with benzos such as:
IV diazepam
IV lorazepam
IM midazolam
**know the appearance of interictal EEG paroxysm, silent period, tonic seizure, clonic seizure, and prostictal depression
Slide 13
name the drugs that block voltage-dependent Na+ channels used for seizures. what specifically do they inhibit the channels from doing?
Phenytoin
Carbamazepine
Lamotrigine
Valproate
Topiramate
Oxcarbazepine
Primidone
– they inhibit high frequency repetitive firing and fast inactivation
what is Lacosamide’s mechanism at voltage-dependent Na+ channels?
likely inhibits slow inactivation
what is Rufinamide’s mechanism? what syndrome is it approved to treat?
may inhibit slow inactivation of voltage-dependent Na+ channels
it is approved to treat Lennox-Gastaut syndrome (a childhood-
onset epilepsy syndrome)
name the drugs that target GABAergic synapses and what specifically they each do
Valproate: modifies amino acid metabolism
Vigabatrin: irreversible GABA-T inhibitor
Tiagabine: preferentially binds GAT-1 (not GAT-2 or GAT-3)
Benzodiazepenes: allosteric modulators of GABA A (enhance affinity/ increase frequency of channel opening)
Barbiturates: allosteric modulators of GABA A (increase efficacy/ duration of opening)
Topiramate: distinct modulator of GABA A
describe the mechanism of gabapentin and pregabalin and an additional thing they are used to treat
Bind a2dsubunit of voltage-operated Ca2+ channels and blocks (Anti seizure activity is most likely to decrease presynaptic release of glutamate)
they are analgesics approved for nerve pain
describe the mechanism of Levetiracetam and Brivaracetam
bind synaptic vesicle protein SV2A and modify release of neurotransmitter (has clear anti-seizure efficacy)
Perampanel:
monotherapy for what category of seizures?
add on therapy for what category of seizures?
drug class?
-Monotherapy for partial seizures
-Add on therapy for generalized seizures
-noncompetitive AMPA receptor antagonist
Felbamate:
used for what category of seizures?
what are the issues with this drug?
when is it used for seizures?
partial seizures
Causes high rate of aplastic anemia and severe hepatitis
as a third-line drug for refractory cases
CBD:
used for what category of seizures?
first in class for rare pediatric epilepsy syndromes
which 2 drugs block T-type Ca2+channels? what does the “T” mean?
Ethosuximide
Valproate
T = Low Voltage Activated Channel
what are the typical Anti-epileptic drug (AED) side effects?
drowsiness, fatigue/mental slowing, dizziness, blurred vision, mood changes, and Many idiosyncratic (individualistic) reactions (rash, gingival
hyperplasia (oral condition that causes your gums to overgrow), bone density loss, hepatotoxicity
Vigabatrin has an FDA black box warning for what reason?
can cause permanent vision loss
what is a specific side effect lamotrigine may cause?
life-threatening skin rash
T/F AED may increase the risk of suicidal thoughts and changes in behavior
true
how do AED effect contraception?
increased oral contraception failure rate
what are the warnings of using AED during pregnancy?
Greater incidence of congenital defects