anticonvulsants 49/50 Flashcards by Elizabeth DeGroot

Phenobarbital (Luminal®)

anti epileptic drug: barbiturate, original, cheap, effective

tonic-clonic and partial seizures
potentiation of synaptic inhibition via GABAa receptor

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Phenytoin (Dilantin®, Diphenylan®)

anti epileptic drug

monotherapy generalized tonic-clonic and partial seizures

Block of voltage gated sodium channels (promote inactive state)

zero-order kinetics

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Carbamazepine (Tegretol®, Carbatrol®)

anti epileptic drug

Block of voltage gated Na+ channels (promote inactive state)

monotherapy generalized tonic-clonic and partial seizures (also used in manic-depressive patients)

self-induced metabolism, also, metabolism increased by pheonbarb/phenytoin

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Ethosuximide (Zarontin®)

anti epileptic drug

mono therapy for absence seizures (altered Ca2+ channel function in thalamus)

Block of T-type calcium channels located on the postsynaptic membrane (thalamus)

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Valproic acid (Depakote®, Depakene®)

anti epileptic drug

monotherapy, tx both absence and tonic-clonic seizures (ALL)

Block of voltage gated Na+ channels (promote inactive state)
AND
Block of T-type calcium channels located on the postsynaptic membrane

increases GABA synthesis

(off-label uses)

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Fosphenytoin (Cerebyx®)

anti epileptic drug

water-soluble pro-drug of phenytoin used for treating status epileptics (given IV)

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Gabapentin (Neurontin®)

Newer anti epileptic drug

GABA molecule bound to lipophillic hexane ring (crosses BBB)

DOES NOT actually interact with GABA receptor, but suppress neuronal activity
binds to L-type Ca channels

Adjunctive tx partial +/- genalized secondary seizures; but mostly used for neuropathic pain

**Not metabolized, excreted unchanged in urine (RFTs before tx)

SE: fatigue, ataxia

(similar drug: Pregabalin (Lyrica®))

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Oxcarbazepine (Trileptal®)

Newer anti epileptic drug

Block of voltage gated Na+ channels (promote inactive state)

monotherapy/adjunctive treatment partial seizures

like carbamazepine, but does not auto induce, but still incr. metabolism of OCTs

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Lamotrigine (Lamictal®)

Newer anti epileptic drug

Monotherapy and adjunctive treatment partial- and generalized tonic/clonic seizures; LGS. Considered a “broad spectrum” AED

prolong rate of recovery of voltage-gated Na+ channels from inactivation, inhibit Ca to lesser extent

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Topiramate (Topomax®)

Newer anti epileptic drug

Monotherapy and adjunctive therapy for partial and tonic/clonic seizures, LGS. Considered a “broad spectrum” AED

Inhibit Na channels and AMPA-kainate receptors enhance GABA receptors

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Levetiracetam (Keppra®)

Newer anti epileptic drug

Adjunctive treatment for partial- and tonic/clonic seizures in adults and myoclonic seizures in children; IV preparation for status epileptics

may prevent presynaptic glutamate release

highest safety margin
highest therapeutic index
3-D “printable” drug

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simple partial seizure

single site within the cortex
preservation of consciousness, short duration 20 – 60 sec

focal motor (e.g. one side of face may twitch)
Jacksonian (“marching” seizure, e.g. muscle twitching “running” up the arm)
somatosensory (varied responses; smelling sulfur, crawling sensation on skin, narrowing of visual field)

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complex partial seizure

single site within the cortex
gradual loss of consciousness, 30 sec – 2 min

may begin with simple seizure, hallucination, strong emotions followed by automatisms (lip smacking, hand wringing, etc)

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EEG can determine ??

type of seizure

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Of the ~10 electrodes placed on the head for an EEG:

if only 1-2 electrodes display synchronous activity during seizure, what type ??

all EEG electrodes will display synchronous activity during a ??

partial seizure

generalized seizure

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if all EEG electrodes display synchronous activity during a seizure

generalized seizure

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generalized seizure

simultaneously in both hemispheres of brain (40% of all seizures)

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absence (generalized)

sudden loss of consciousness, less than 30 sec

staring and blinking (3/sec)
body may remain active
ADHD, impaired learning

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tonic-clonic (grand mal, gen)

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sudden loss of consciousness, 1.5 to 2.5 min

20 sec of muscle rigidity followed by 1 – 2 min of rhythmic muscle contractions (clonic)

injury when falling during tonic stage, loss of bowel control

Phenobarbital (Luminal®) SEs

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sedation, irritability/hyperactivity (kiddos), rash

*metabolized by CYP2C9, induction of CYP3A4–> inc. metabolism of OCTs and teratogenic

anticonvulsant drug MOA

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reduce neuronal activity

drugs that enhance inhibitory effects of GABA

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Barbs (Phenobarbital and primidone) and benzos (clonazepam, diazepam) increase GABA effects at GABAa

tiagabine: inhibit the re-uptake of GABA
vigabatrin: irreversible inhibitor of the GABA-degrading enzyme GABA transaminase

monotherapy will sufficiently control seizures for

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70% of epileptic pts

original seizure tx

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bromides

barb less effective than phenobarbital SEs??

primidone dizziness, nausea, nystagmus, ataxia (dec. firing)

Phenytoin SEs

gingival hyperplasia SJS: only in first few months of tx interact with warfarin and OCTs and may cause birth defects

Carbamazepine SEs

Acute: stupor, coma, hyperirritability convulsions Chronic: drowsiness, vertigo, ataxia, blurred vision. Induces CYP3A4 resulting in increased drug metabolism (e.g. oral contraceptives)

benzos can be used for ??

adjunctive treatment only of absence seizures and juvenile myoclonic seizures

newer AEDs

lack serious side effects (less SJS) do not induce liver enzymes (fewer drug-drug interactions) less efficacious mostly approved for adjunctive treatment (combo tx)

Lennox-Gustaut syndrome

Childhood-onset epilepsy Severe cognitive dysfunction Multiple seizure types including atonic or “drop” seizures (cause of injury) Resistant to drug therapy (tx with Felbamate) Mortality rates 3 – 7% ketogenic diet

partial seizure tx (or secondarily generalized)

carbamazepine phenytoin alternative: lamotrigine (broad-spec) valproic acid

generalized: absence seizure tx

Ethosuximide Valproic acid* alternative: Clonazepam

generalized: tonic-clonic tx

Carbamazepine Phenytoin Valproic acid* alternatives: Lamotrigine* Topiramate*

Status Epilepticus

a series of seizures (any type) where full recovery from one seizure does not occur before onset of next seizure 20% mortality rate

Status Epilepticus tx

lorazepam IV IV fosphenytoin (Cerebyx®) (water soluble prodrug of phenytoin-which would irritate veins) levetiracetam (alternative to fosphenytoin) phenobarbital and valproic acid (Depacon®)

long term use of AEDs may cause

osteoporosis: | altered vitamin D metabolism in the liver-->lower bone density

AEDs: OCT interactions safe for preggos?? specifically ?? most common offending drug ??

3X higher failure rate of the contraceptive NO, 2 – 3 fold increase in birth defects neural tube formation abnormalities resulting in facial and cranial deformities phenytoin (all AEDs may cause similar birth defects)

To reduce the likelihood of neural tube birth defects the patient should be given ???

folate (0.4 mg/day) throughout pregnancy vitamin K (10 mg/day) during last month of gestation to help reduce newborn blood coagulation problems/Vit K deficiencies

treating epilepsy with ??? is controversial

generic drugs, use brand names

teratogenic AED

valproic acid

for pregnant/soon to be pregnant pts...

do not discontinue tx (do not want break thru seizures) | but reduce to mono therapy and monitor drug plasma levels/seizure activity, lowest dose possible is desired

ethosuximide SEs

Nausea, vomiting, anorexia CNS drowsiness, lethargy, euphoria SJS, aplastic anemia

Valproic acid SEs

GI nausea, anorexia CNS sedation, ataxia, tremor Increase in hepatic blood enzymes (40%) Hepatic toxicity in patients

Lamotrigine SEs

dizziness, ataxia, blurred vision, nausea | Rash and SJS when used in addition to other AEDs

Topiramate SEs

Ataxia, fatigue, somnolence, weight loss | Reduces plasma levels of estradiol and oral contraceptives

Levetiracetam SEs

somnolence, dizziness, asthenia , no drug-drug interactions |

anticonvulsants 49/50 Flashcards

(46 cards)