Anti-Epileptics Flashcards
Screening test for Absence seizure drugs
Pentylenetetrazol
Screening test for GTCS and complex partial seizure drugs
Maximal Electroshock Test
MOA of drugs identified by Maximal Electroshock Test
prolonged inactivation of VG Na channels
Drugs that inhibit presynaptic glutamate VG Na channels
Lancosamide
Lamotrigine
Carbamezapine
Phenytoin
Drugs that inhibit presynaptic glutamate VG Ca channels
Ethosuximide
Lamotrigine
Pregabalin
Gabapentin
Drugs that inhibit presynaptic glutamate K channels
Retigabine
Drugs that inhibit glutamate SV2A (synaptic vesicle protein)
Levetiracetam
Drugs that inhibit presynaptic glutamate CRMP-2
Lacosamide
Drugs that inhibit postsynaptic glutamate AMPA receptors
Phenobarbital
Topiramate
Lamotrigine
Drugs that inhibit postsynaptic glutamate NMDA receptors
Felbamate
Drug that inhibits GAT-1
Tiagabine
Drug that inhibits GABA-T
Vigabatrin
Drugs that act on GABAa receptors
Benzo & Phenobarbital
MOA of tiagabine
Inhibits GABA reuptake by blocking GAT-1
MOA of vigabatrin
Prolongs GABA half life by blocking degradation via GABA-T
Hallmark of simple partial seizure
presevation of consciousness
Usual location of complex partial seizure
bilateral limbic system
Hallmark of complex partial seizure
automatism
Feature of secondarily generalized seizure
Amnestic
Length of tonic phase of GTCS
15-30sec
length of clonic phase of GTCS
60-120 sec
Seizure type with sudden onset and abrupt cessation
Petit mal (absence)
Duration of Absence seizures
10-45 sec
Age of onset of absence
childhood or adolesence
EEG findings of absence
2.5-3.5Hz spike and wave pattern
Presentation of atonic seizure
sudden loss of postural tone
Basis of epileptic treatment
empiric seizure classification
When is multipple drug therapy needed?
when two or more types of seizure occur in the same patient
How to discontinue anti-epileptics
reduce dose gradually
Most common cause of failure of therapy
faulty compliance
N substitution of heterocyclic ring
hydantoin
CN substitution of heterocyclic ring
Barbiturates
O substitution of heterocyclic ring
Oxazolidinedione
C substitution of heterocyclic ring
Succinamides
NH2 substitution of heterocyclic ring
Acetylureas
Conventional drugs used for all partial seizures and GTCS
Carbamenzapine, Phenytoin, Valproate
Conventional drugs for Absence
Ethosuxamide, Valproate
Conventional drug for myoclonic seizure
Valproate
Structure of phenytoin
diphenolhydantoin
2 phenols + hydantoin (N)
Substitution responsible for sedation
alkyl
Major MOA of phenytoin
block presynaptic VG Na channels in inactive state
reason for use dependent effect of phenytoin
preferential binding to and prolongation of inactivated state of VG Na channel
Presynaptic effects of phenytoin
decrease glutamate release
inscrease GABA release
Amount of absorption of phenytoin salt in GI tract
almost complete
Therapeutic levels of Phenytoin
10-20 mcg/mL
Oral therapy dose for adults (Phenytoin)
start at 300mg/day
Relationship between phenytoin dose and plasma concentrations
Non-linear (metabolism is saturable)
Why is Phenytoin not recommended to be given IM
drug precipitation in muscle occurs & unpredictable absorption
Drug interaction of Pheytoin
Enzyme INDUCER
Most common ADR of Phenytoin
diplopia and ataxia
gingival hyperplasia and hirsutism (less common)
ADRs of long term use of phenytoin
Coarsening of facial features, mild peripheral neuropahty, osteomalacia
Prodrug of Phenytoin
Fosphenytoin
Advantage of Fos phenytoin over phenytoin
more soluble
Fosphenytoin IV indication
convulsive status epilepticus
DOC for convulsive status epilepticus
Fosphenytoin IV
Sites of accumulation of Fosphenytoin
brain, liver, muscle, and fat
CSF concentration of Fosphenytoin
CSF concentration proportionate to free plasma level
After therapeutic level of drug is attained, how will small rises in drug level affect patient’s physiologic response?
toxicity symptoms due to saturation of metabolism
Toxicity of rapid IV push Fosphenytoin
cardiac arrhythmias
Moeity in carbamazepine structure
ureide
Indications of Carbamazepine
Trigeminal neuralgia
Neuropathic pain
Manic-depressive pX
Anti-epileptic drug used for trigeminal neuralgia
Carbamanzepine
AED drug similar to imipramine and other anti-depressants
Carbamazepine
MOA of carbamazepine
block presynaptic VG Na channels in inactive state
Is carbamazepine sedating?
No carbamazepine is not sedating
Drug interaction of Carbamanzepine
Enzyme INDUCER
can increase metabolism of Primidone, Phenytoin, Ethosuximide, Valproic Acid, Clonazepam
Active metabolite of carbamanzepine
Carbamazepine-10,11-epoxide
Therapeutic level where you may experience diplopia with carbamazepine
7mcg/mL
Drug interaction of Valproic Acid
Enzyme Inhibitor
Drug interaction of Phenobarbital
Enzyme INDUCER
Most common dose-related ADR of Carbamazepine
Diplopia and ataxia
Most common idosyncratic ADR of carbamazepine
erythematous skin rash
Most fatal idosyncratic ADRs of carbamazepine
blood dyscrasias, aplastic anemia, agranulocytosis within 4 months of treatment
Recommended action for carbamazepine toxicity
careful monitoring rather than discontinuation (unless persistent)
Benefit of Oxcarbazepine over carbamazepine
improved toxicity profile
Other dose-related ADRs of carbamazepine
mild GI upset
Hyponatremia
H2O intoxication
Metabolite of Oxcarbazepine
Eslicarbazepine both R- and S+ form (excreted as gluconoride)
Chirality of Eslicarbazepine
S+ enantiomer
Toxicity profile of oxcarbazepine
less hypersensitivity
Hyponatremia is more common
Indication for Eslicarbazepine Acetate (ESL)
adjunct or monotherapy for partial onset seizure
drug that has autoinduction (enzyme inducer of itself)
carbamazepine
ADR of eslicarbazepine acetate
headache, dizziness, nausea
Rare: hyponatremia, hypersensitivity, suicidal ideation (stronger in carbamazepine and oxcarbazepine)
Drug with effect on oral contraceptives (and it’s effect)
Eslicarbazepine
decreases ethinylestradiol and levonorgestrel
Metabolite of eslicarbazepine acetate (ESL)
Eslicarbazepine S+ only
Metabolite of Fospheytoin
Phenytoin
Most potent between carbamazepine, oxcarbazepine, and eslicarbazepine?
carbamazepine (also most ADRs)
Oldest non-sedative AED
Phenytoin
Oldest of the current AED
Phenobarbital
Is phenobarbital sedating?
Yes phenobarbital is sedating
When is phenobarbital a DOC
in infants only
DOC for infants
phenobarbital
MOA of phenobarbital (in relation to GABA)
Binds to GABAa Receptor allosterically to keep it open LONGER
(increase GABA effect)
What type of channel is GABAa
Cl- channel
pH reading of phenobarbital
weak acid (therefore increased absorption when plamsa is acidic and decreased absorption if plasma is basic)
Mephobarbital structure
methylated phenobarbital
metharbital structure
methylated barbital
Primidone structure
2-desoxyphenobarbital
Metabolites of Primidone
Phenobarbital
Phenyethanolamide (PEMA)
MOA of Primidone
block presynaptic VG Na channels in inactive state
Prodrug of phenobarbital and Phenylethanolamide
Primidone
Most effective plasma level of Primidone
8-12mcg/mL
third line drug for partial seizures (refractory cases)
Felbamate
Indication for felbamate
third line for partial seizures (refractory)
Lennox-Gastaut syndrome
MOA of felbamate
use-dependent block of NMDA receptor (post synaptic Glutamate receptor)
Potentiates GABA a Receptor
Lennox Gastaut Syndrome
epilepsy with different types of seizures (mostly tonic and atonic)
usually impaired cognitive function
EEG slowing and spike wave burst less than 2.5 Hz
Therapeutic effects of Gabapentin and Pregabalin
anti-seizure and analgesic
MOA of Gabapentin and Pregabalin
bind to VG Ca channels (presynaptic Glutamate)
= decrease in glutamate secretion
True of False Gabapentin and Pregabalin can act directly on GABA receptors
False they do not act directly on GABA receptors even if they are GABA analogs
but they may act indirectly to increase GABA release
ADR of Gabapentin and Pregabalin
Somnolence, dizziness, headache, ataxia, tremors
Are Gabapentin and Pregabalin sedating?
Yes they are sedating
Drug interaction of Gabapentin
NO enzyme induction (negligable drug interactions)
Indications for Gabapentin
Adjunct for partial and generalized T-C seizures Monotherapy (but in high doses) Neuropathic pain (POST HERPETIC NEURALGIA)
AED for post-herpetic neuralgia
Gabapentin
Indications for Pregabalin
Adjunct for partial and generalized T-C seizures
Neuropathic pain (POST HERPETIC NEURALGIA, DM NEUROPATHY, FIBROMYALGIA)
Generalized Anxiety disorder
1st drug approved for Fibromyalgia
Pregabalin
AED that can be used for generalized anxiety disorder
Pregabalin
MOA of Lacosamide
enhances SLOW inactivation of presynaptic glutamate VG Na channels (other AEDs prolong FAST inactivation)
Binds to presynaptic glutamate CRMP-2
Chirality of Lacosamide
R(+) enantiomer
indication fro Lacosamide
adjunct for patial seizures (w/ or w/o secondary generalization)
Age to prescribe Lacosamide
> 16y/o
ADRs of Lacosamide
Dizziness, headache, Nausea, Diplopia
Drug interaction of Lacosamide
NO induction/inhibition of enzymes (negligable drug interaction)
MOA of Lamotrigine
Blockage of presynaptic glutamate VG Na channels
Inhibit presynaptic glutamate Ca channels
Indication of Lamotrigine
Monotherapy: Partial seizures, Absence, myoclonic seizures, Lennox-Gastaut
Bipolar Disorder
AED used for Bipolar disorder
Lamotrigine
ADRs of Lamotrigine
Somnolence, dizziness, headache, Nausea, Diplopia
Is lamotrigine sedating?
Yes it is sedating
MOA of Levetiracem
binds selectively to the synaptic vesicular protein SV2A`
Drug interaction of Levitiracem
NO induction/inhibition of enzymes (negligable drug interaction)
Indication of Levetiracem
Adult: Partial seizure
Children: Primary GTCS and Juvenile Myoclonic seizure
ADRs of Levetiracem
Somnolence, Dizziness, Ataxia, ASTHENIA
Is levetiracem sedating
Yes it is
MOA of Retigabine or Ezogabine
K channel facilitator via KCNQ gene
Retigabine Indication
Partial seizure in adults
ADRs of Retigabine
Somnolence, dizziness, confusion, blurred vision, DYSARTHRIA
MOA of Tiagabine
inhibit GABA reuptake via GAT-1 inhibition
Tiagabine indication
Primary GTCS
ADRs of Tiagabine
Nervousness, dizziness, difficulty concentrating, DEPRESSION, tremor
MOA of topimarate
blockade of VG Na channels
Blocks postsynaptic glutamate AMPA receptors
Topimarate indication
Monotherapy: partial and genralized T-C seizure, Lennox Gastaut Seizure
ADRs of Topimarate
Somnolence, dizziness cognitive slowing, nervousnessm fatigue, paresthesias
MOA of Vigabatrin
Irreversibly inhibits GABA-T = inhibited degradation of GABA
Effect of Vigabatrin of GABAa Receptors
Desensitization due to increased GABA levels and prolonged activation
Indication of Vigabatrin
Partial seizures and infantile spasms
Which is the active enantiomer of vigabatrin
S+
ADRs of Vigabatrin
WEIGHT GAIN, drowsiness, dizziness, peripheral visual field defects
Structural substitution of ethosuxamide
Succinamide (C)
Indication of ethosuxamide
pure petit mal drug
Most commonly used petit mal drug
Ethosuxamide
Compare Phensuxamide and Metgsuxamide with ethosuxamide
Phensuxamide: less effective
Methsuxamide: more toxic
MOA of ethosixamide
Effect on presynaptic glutamate Ca channels
Reduce low threshold T-Type Ca current in thalamic neurons
3 drugs for Absence seizure
Ethosuxamide & Valproate > Lamotrigine
Structure of Valproic Acid and Sodium Valproate
Fatty carboxylic Acid
Active form of Valproic Acid and Sodium Valproate
Valproate
at what pH is valproic acid fully ionized
body pH (therefore it turns into active form in the body – valproate)
MOA of Valproate
Blocks Na currents
Block NMDA receptor mediated excitation
Inhibit GAT-1 (reuptake)
Facilitate glutamic acid decarboxylase (GABA synthesis)
Indications of Valproate
BROADD
Preferred in absence over ethosux only if with concomitant GTCS
Myoclonic seizure (unique and very dramatic)
Bipolar Disorder
Migraine Prophylaxis
AED effective for migrane prophylaxis
Valproate
Drug interaction of Valproate with phenytoin
Valproate + Phenytoin = displace phenytoin from plasma proteins
ADRs of Valproate
GIT disturbance (common dose-related) Fine tremors (high levels) WEIGHT GAIN, hair loss (uncommon) Hepatotoxicity (Idiosyncratic) TERATOGENIC (Spina bifida, CVS, orofacial, digital deformities)
Trimethadione structural substitution
oxazolidinedione
Indication of thrimethadione
PREVIOUS DOC for absence (replaced by ethosuxamide)
active metabolite of themethadione
dimethadione
MOA of trimethadione
raises threshold for seizure discharge after repetitive thalamic stimulation (Ca current)
How do you supress absence seizures?
inhibiting pacemaker action of thalamic neurons (Ca current)
ADRs of Trimethadione
Sedation
CI w/ pregnancy
Indication of Diazepam
DOC for status epilepticus (IV)
Limit of Diazepam use for seizure control
tolerance develops to oral meds (not useful for long term) and sedation
Indication of Lorazepam
Status epilepticus IV
Lorazepam benefits over Diazepam
more effective and longer acting then diazepam
Easier to administer in IV (water based)
Indication for Clonazepam
Absence
Myoclonic seizure
Infantile spasms
(long acting and very potent)
Indication for Nitrazepam
Myoclonic seizure
Infantile spasm
Indication for clorazepate dipotassium
Adjunct for complex partial seizure in adults
Less sedating benzodiazepam
clobazam
Active metabolite of clobazam
norclobazam
MOA of Acetazolamide
carbonic acid anhydrase inhibitor
Depolarizing effect of bicarbonate ions in neurons via GABA R ion channes may be diminished
Limiting factor to Acetazolamide use
Tolerance
Indication for Acetazolamide use
women with seizure exacerbation during menstruation
DOC for inflantile spasms
Vigabatrin
Drugs that work on infantile spasms
IM corticotropin or oral prednisone
Benzos (clonazepam or nitrazepam)
Vigabatrin (DOC)
Most common status epilepticus
GT-T status epilepticus
Definitive therapy for statue epilepticus
phenytoin
Phenobarbital (if refractory to phenytoin)
teratogenic effect of Phenytoin
fetal hydantoin syndrome
cleft lip/palate, congenital heart disease, slowed growth, mental deficiency
Teratogenic effects of Valproate
Spina Bifida
Drugs that are most difficult to discontinue
barbiturates and benzodiazepams (weeks-months)
When do you try to discontinue drugs?
when patient has been seizure free for 3-4 years
Most dangerous effect of AED
respiratory depression (potentiated by alcohol)
Treatment for overdose
supportive
do not use stimulants
ALKALINIZE URINE
3 drugs that can be used for all types of seizures
valproate, topiramate, lamotrigine