Anticonvulsants Flashcards
5 questions
the clinical manifestation of an abnormal and excessive excitation of a population of neurons
seizure
a tendency toward recurrent seizures unprovoked by systemic or neurologic insults
epilepsy
occurs with an aura, epileptic cry, loss of consciousness and postural tone, tonic spasm of entire body, synchronous clonic movements, followed by confusion and sleep
tonic-clonic (grand mal)
brief loss of consciousness (5-10 secs), with local or widespread clonic movements (minor muscle twitching without loss of postural tone)
petit mal (absence)
in which patients do petit mal (absence) occur?
children
continuous or repeated attacks, can be grand mal or petit mal
status epilepticus
in which 2 acute disorders affecting the brain can status epilepticus occur in?
meningitis
encephalitis
individual remains conscious, is limited to certain muscles, specific sensory changes, and autonomic activity; may remain localized or may spread causing progressive symptoms
simple partial seizure
which seizure type is associated with Jacksonian Epilepsy?
simple partial seizure
impaired consciousness, usually originate in temporal or frontal lobes but spread to broader areas; cause flashbacks and stereotypes movements like chewing
complex partial seizures
what does treatment of a partial seizure evolving to a generalized seizure depend on?
type of generalized seizure that is triggered
what is more refractory to drug treatment than the common generalized seizures?
partial evolving to generalized
what is the pathophysiology of most seizures?
unknown etiology
what do antiepileptic drugs treat?
symptom of seizure
NOT underlying epileptic condition
what is the goal of antiepileptic drugs?
maximize QOL by minimizing seizures and ADRs
which 3 anticonvulsants decrease the excitability of the focus?
phenobarbital
primidone
ethosuximide
which 4 anticonvulsants prevent the spread of nervous activity?
phenytoin
phenobarbital
carbamazepine
valproate
which 4 anticonvulsants enhance inhibitory mechanisms?
phenobarbital
primidone
valproate
benzodiazepines
all anticonvulsants are specific for seizure type, except which one that is used for all types of seizures?
valproic acid
what are many anticonvulsants used for?
neuropathic pain
very painful, sharp electric-like spasms that usually last a few seconds-mins but can become constant
trigeminal neuralgia
what activities can trigger trigeminal neuralgia? (5)
brushing teeth
chewing
drinking/eating
lightly touching face
shaving
what is a risk factor for trigeminal neuralgia?
age (after 40)
what is the major cause of trigeminal neuralgia?
demyelination of the axons of the trigeminal nerve
what are 2 other uses of anticonvulsants?
diabetic pain
bipolar disorder
sedation can occur at therapeutic doses of anticonvulsants, except in these meds: (2)
phenytoin
valproic acid
why are there potential drug interactions with anticonvulsants?
highly protein bound
why do some anticonvulsants reduce antibiotic efficacy?
some induce hepatic enzymes
which 2 drug types decrease anticonvulsant absorption?
antacids
antihistamines
the first drug developed specifically to treat seizures and is non-sedating
phenytoin
what is the drug of choice for generalized tonic-clonic seizures?
phenytoin
what are the 4 uses for phenytoin?
generalized tonic-clonic seizures
partial seizures
status epilepticus
trigeminal neuralgia
phenytoin is used as a backup treatment for _____
trigeminal neuralgia
drug that inhibits reactivation of Na channel and prevents post tetanic potentiation
phenytoin
what increases the effectiveness of phenytoin in its MOA?
high extracellular K
what does phenytoin do at greater than therapeutic concentrations?
interferes with Ca channel and neurotransmitter release
what is special about phenytoin’s elimination?
has zero order kinetics at high doses (small increment of dose leads to toxicity)
what is the highest protein-bound anticonvulsant?
phenytoin (90%)
a patient taking phenytoin is experiencing nystagmus, diplopia, thought disorders and sedation. what is their plasma level?
20
a patient taking phenytoin is experiencing loss of consciousness, confusion, and hyperactivity. what is their plasma level?
30
a patient is taking phenytoin is experiencing lethargy, stupor, and coma. what is their plasms level?
40
what are the ADRs of phenytoin?
P450 inducer
Hirsutism
Enlarged gums
Teratogenic
Osteomalacia
Intereferes with B12 = megaloblastic anemia
what can be used to treat blood dyscrasias side effects of phenytoin?
folate
what can be used to prevent osteomalacia side effect of phenytoin?
vitamin D supplements
what is the drug of choice for trigeminal neuralgia?
carbamazepine
what are the 3 uses for carbamazepine?
trigeminal neuralgia
generalized tonic-clonic seizures
partial seizures
drug that inhibits high frequency neuronal firing, inhibits reactivation of Na channels, and inhibits Ca influx
carbamazepine
what is the half-life of cabamazepine?
10-20 hours
what are the 5 ADRs of Carbamazepine? PATCH
Parkinsonism (involuntary movement)
Aplastic anemia / Agranulocytosis
Teratogenic / Taste disorder
Convulsions / CNS (dizziness, slurred speech, ataxia)
Headache
a patient presents with dizziness, diplopia, drowsiness, ataxia, and slurred speech. what are they experiencing?
carbamazepine overdose
one of the oldest, most effective and least toxic anticonvulsants that is the drug of choice for seizures in infants; particularly febrile
phenobarbital
what are the 3 uses for phenobarbital?
febrile seizure in infants
generalized tonic-clonic
partial seizures
drug class that enhances the binding to GABAa receptors, increasing Cl channel openings, which inhibits Ca currents, leading to decreased excitability
barbituates
phenobarbital
primidone
what is the half life of phenobarbital?
50-140 hours
what inactivates phenobarbital?
liver enzymes
phenobarbital decreases the efficacy of what drugs?
tetracycline + other antibiotics
how can we measure the plasma concentration of phenobarbital and other antiepileptics?
saliva
what are the 2 uses for primidone?
generalized tonic-clonic seizures
complex partial seizures
what is the difference between primidone and phenobarbital in their PK?
primidone is completely absorbed after oral administration
what is the half life of primidone?
5-15 hours
what are the 5 ADR of phenobarbital and primidone (barbituates)?
sedation
depressed cardio/pulm
hepatotoxicity
megaloblastic anemia
osteomalacia
phenobarbital is not teratogenic, but enhances teratogenicity of ______when combined
phenytoin
what are 2 ADR specific to primidone?
acute toxicity
acute psychosis in complex partial seizures
what is the drug of choice for absence seizures?
ethosuximide
which drug inhibits Ca channels through T-type Ca channels = reducing oscillatory behavior of thalamic neurons?
ethosuximide
how can plasma concentration of ethosuximide be measured?
saliva
what are the 4 ADR of ethosuximide?
Gi distress
CNS depression (transient)
bone marrow depression
blood dyscrasias
what is the preferred drug in pregnancy?
ethosuximide
which drug prolongs the activation of Na channel, leading to decreased repetitive neuronal firing, inhibits T-type Ca channels, and increases GABA levels at higher than therapeutic doses?
valproic acid
what are the 5 uses for valproic acid?
absence seizures
tonic-clonic seizures
myoclonic seizures
partial seizures
neuropathic pain
what is the half-life of valproic acid?
10-15 hours
how is valproic acid excreted?
in urine
what are the 4 ADR of valproic acid? HATS
Hepatotoxicity
Abdominal (GI) distress
Teratogenic
Sedation
which drug class enhances the binding of GABA to GABAa receptors, increasing the frequency of opening GABA Cl channels? and at higher concentrations, act on Na channels like phenytoin and carbamazepine?
benzodiazepines
clonazepam
clorazepate
diazepam
lorazepam
what are the 2 uses for clonazepam?
“the clone makes the myoclonic absent”
absence seizures
myoclonic seizures
what is the use for clorazepate?
“the lor is only partially correct”
partial seizures
which 2 benzodiazepines can treat status epilepticus?
diazepam
lorazepam
the major metabolite of clorazepate and diazepam that has anticonvulsant activity
desmethyldiazepam
what are 2 ADR of benzodiazepines?
tolerance w/ 1-6 mo of treatment
hyperactivity in children
which drug binds to voltage dependent Ca channels, and has a GABA analogue but does not interact with GABA receptors?
gabapentin
what are the 3 uses of gabapentin?
partial seizures
trigeminal neuralgia
neuropathic pain
how is gabapentin excreted?
renal, unchanged
what are the 2 uses for lamotrigine?
partial seizures
bi-polar depression
MOA of lamotrigine?
acts on Na channels
what is the ADR of lamotrigine?
“lamotrigine is a lamo and causes SJS”
stevens-johnson syndrome; severe skin rash
what drug reduces lamotrigine half life from 24 to 12 hours? why?
carbamazepine
induces liver enzymes
which drug increases lamotrigine half life up to 60 hours?
valproate
what is the use for felbamate?
partial seizures
what is the major ADR of felbamate? what did that lead to?
aplastic anemia
bone marrow transplants
which drug is only approved for restricted use?
felbamate