Anti-Convulsants Flashcards
Complex waves on an EEG
are summation of simple waves
dx of seizure focus can occur by EEG or____
single photon emission coherence topography (SPECT), measures regional BF in the brain; image shows increases in BF in the area associated with onset of a seizure in the same area
seizures secondary to what can cause irreversible brain damage
stroke/trauma
partial epilepsy
originates in a small group of neurons that constitute a seizure focus
symptoms depends on site of focus and extent to which electrical activity spreads
subtype: simple, complex
Contained in 1 hemisphere, can spread to generalized
generalized epilepsy
seizures spread across both hemispheres (cortical and subcortical), convulsive/non-convulsive, associated with an immediate loss of consciousness; starts as a partial seizure
subtypes: tonic-clonic, absence, myoclonic, febrile seizures in children, status epilepticus
simple partial seizure
sym: depend on site of focus and spread, consciousness is unimpaired, little spread (10%)
only a couple EEG waves read abnormally
complex partial seizure
consciousness is impaired, may spread across cortex processing to a secondary generalized seizure; spread throughout hemisphere (35%)
generalized: tonic-clonic
tonic:
generalized: absence
3-5 sec, eyes flutter; 10%
generalized myoclonic
brief muscle contractions that may reoccur for several minutes; rare, occurs at any age, often a result of brain damage
generalized: febrile
3mo-5yo
typically during illness/high fever
usually benign
rarely req meds
generalized: status epilepticus
medical emergency systemic hypoxia acidemia hyperpyrexia CV collapse brain damage 1) rapid-acting drugs IV and support of CV and resp systems 2) long acting drugs IV (phenytoin)
phenytoin
drug of choice: adult epilepsy (initial)
blocks Na channels (and some Ca channels), suppresses repetitive AP firing
supresses: partial (both) and tonic-clonic, IV for status
NOT USED FOR ABSENCE
-high PRO bound
metabolized by P450 (CYP), saturate at high dosage
Interactions: doxycyline, cyclosporine
SE: gingival hyperplasia, megaloblastic anemia, teratogenic effects
alt: fosphenytoin (prodrug) for IV/IM use
Carbamazepine
MOa: blocks Na channels (somewhat Ca channels), suppresses Ap firing and propagation of abnormal waves throughout brain
Drug of choice for simple, partial complex, tonic-clonic
other: trigeminal neuralgia/bipolar d/o
PK: highly lipid soluble: rapid CNS penetration
Metabolized by CYPs –induces CYPs, increases own metabolism
drug interactions: enhances CYPs increasing metabolism of some anti-epileptics (phenytoin)
carbamazepine metabolism inhibit by many drugs
SE: hepatotoxicity, teratogenic effects
valproate
MOA: blocks Na and Ca channels, to some extent GABAergic signaling, reduces propagation of abnormal electrical discharge in brain
Drug of choice: myoclonic seizures, second line to tonic-clonic and absence (hepatotox)
PK: high PRO bound, metabolized by CYP
SE: nausea
divalproex
combo of sodium valproate and valproic acid, improved GI tolerance
ethosuximide
MOA: inhibits T-type Ca channels, controls rhythmic depolarization of thalamic neurons during absence seizures
DOC: absence
PK: not bound to plasma PRO
75% metabolized by CYP, 25% urinated no change
phenobarbital
barbiturate
used to rx simple partial, recurrent tonic-clonic, febrile seizures
-used in combo with carbamazepine allows for use of smaller doses
-also used to rx anxiety
MOA: facilitates GABAR activation ot increase inhibit
PK: freely penetrates brain, 75% inactivated by hepatic microsomal system
SE: teratogenic effects, megaloblastic anemia
primidone:
prodrug, effects comes from metabolite phenobarb
diazepam
benzodiazepine
Drug of choice: emergent Rx of seizure or status
tolerance: after 1-6 mo
-potentiates GABAR activation to increase inhibitory tone
lorazepam
benzodiazepine
Drug of choice: emergent Rx of seizure or status
tolerance: after 1-6 mo
-potentiates GABAR activation to increase inhibitory tone
clonazepam
benzodiazepine
used for myoclonic and absence seizures
potentiates GABAR activation to increase inhibitory tone
tolerance develops after 1-6 months
lamotrigine
possibly inhibits glutamate release by inhib Ca channels, also inhibits Na channels, suppresses repetitive AP firing rx partial (both) and tonic-clonic -1/2 life is decreased by enzyme inducing drugs (carbamazepine, phenytoin), increased by valproic acid
gabapentin
-unclear MOA: may enhance GABAR activation, inhibits glutamate release by Ca+ channel blockage
-rx partial seizures, generalized tonic-clonic seizures
PK: not metabolized, does not induce CYP
-no PRO binding
-negligible interax
pregabalin
MOA: blocks Ca channels and gluamate release
rx partial seizures
SE: thrombocytopenia
topiramate
rx partial seizures and tonic-clonic seizures, blocks Na channels and increases post-synaptic GABAR activity
levetiracetam
rx partial and tonic-clonic
-modifies glutamate and GABA release by binding to synaptic PRO SV2A
