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Chapter 21Drugs Treating Seizure Disorders
Chapter 21Drugs Treating Seizure Disorders
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SeizuresSeizures
What are they ?
How are they caused?
Which patients can have a seizure?
How are they treated ?
What are the side effects or precautions for
the patient ?
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EpilepsyEpilepsy
Epilepsy is a group of neurologic disorders in which CNSneurons display hyperexcitability
Seizures are a result of excessive neurologic activity.Manifestations are displayed as either:
loss of consciousness with generalized muscletwitching
mild alterations in consciousness with repetitiveblinking.
Patients with patterns of seizures who are diagnosedwith epilepsy are treated with antiepileptic drugs.
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Pharmacodynamics of Antiepileptic DrugsPharmacodynamics of Antiepileptic Drugs
The 3 main ways that antiepileptic drugs work:
Decreasing the rate at which sodium flows intothe cell
Prototype : Phenytoin
Inhibiting calcium flow rate into the cell throughspecific channels
Prototype: Ethosuximide Increasing the effect of the neuroinhibitor
gamma-aminobutyric acid (GABA)
Prototype: Benzodiazepines
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Physiology of NeurotransmittersPhysiology of Neurotransmitters
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PathophysiologyPathophysiology
When a group of neurons exhibits coordinated, high-frequencydischarge, it is termed a focus.
The causes of a focus include:
head trauma tumor growth
hypoxia inherited birth defects
Seizures result from :
a focus which spreads to other areas of the brain
additional neurons join in the hyperactivity
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PathophysiologyPathophysiology
Seizures may result from either:
high levels of glutamate
low levels of GABA
Classification of seizures depends on how widespreadis the neural hyperactivity
Partial seizures occur when focus activity islimited to a specific area of the brain
Generalized seizure occurs when focus activityspreads within both hemispheres of the brain
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Classifications of SeizuresClassifications of Seizures Partial - involves only one hemisphere of brain
Simple ( consciousness not impaired)
Complex ( consciousness impaired)
Generalized - involves both hemispheres
loss of consciousness
tonic-clonic phase ( grand mal)
initially stiffness & rigidity
LOC, massive muscle spasms
urinary / bowel incontinence
post ictal state follows convulsion
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Emergency : Status EpilepticusEmergency : Status Epilepticus
One seizure follows another
No recovery of consciousness in between seizures Any grand mal seizure that lasts longer than 5 minutes
Any grand mal seizure has the potential to become statusepilepticus
Most common reasons for status epilepticus:
alcohol withdrawal
stopping antiepileptic drug therapy
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Febrile Seizures in ChildrenFebrile Seizures in Children
Febrile Seizures occur in children with high fevers
Generalized seizure activity occurs These are common and do not increase the risk of
developing epilepsy
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Other causes of generalized seizureactivityOther causes of generalized seizureactivity
Seizures may also occur from known and reversiblecauses: ( any patient has the potential to develop aseizure)
Metabolic abnormalities:
hypoglycemia
electrolyte imbalance
brain infection ( meningitis)
uremia
pre-eclampsia or toxemia of pregnancy
drug and alcohol abuse
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Antiepileptic Drugs That Decrease SodiumInfluxAntiepileptic Drugs That Decrease SodiumInflux
Control seizures by q sodium influx into the cells.Remember :
Sodium influx into the cells produces an action potential
Action potential causes neurons to fire
Prototype drug: phenytoin (Dilantin)
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Phenytoin: Core Drug KnowledgePhenytoin: Core Drug Knowledge
Pharmacotherapeutics
Control partial and generalized seizures
Prevent and treat seizures post neurosurgery
Treat status epilepticus after administering a benzodiazepine
Normal blood level : 10-20 mcg/ ml
Small changes in the dose may produce larger than expectedchanges in the serum concentration of the drug
Great variability exists among how individuals metabolize this
Slight deviations from the therapeutic range may produce:non-therapeutic effects or adverse effects
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Phenytoin (Dilantin)P
henytoin (Dilantin) Pharmacokinetics
Absorbed slowly orally ( but common route )
IM absorption very erratic precipitates at the
injection siteIV administration effective : cant be mixed with
Dextrose
Highly protein bound (90%)
Half life at therapeutic levels is 20 60 hours
Metabolized in the liver ( to an inactive metabolite)
How quickly this biotransformation occurs has a limit p
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Phenytoin ( Dilantin)Phenytoin ( Dilantin) Pharmacodynamics
primary site of action : motor cortex
binds to Na channels (while in the inactive state)
delays the return of the channel to an active state
(remember Na can only enter the channel and initiatean action potential when the channels are in an activestate)
time between action potentials is lengthened
neurons cannot fire now at an excessive rate
excessive muscle contractions (as in grand mal
seizures are prevented)
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Phenytoin: Core Drug Knowledge (cont.)Phenytoin: Core Drug Knowledge (cont.) Contraindications and precautions
Bradycardia and heart block ( because it can also affectthe Na channels in the cardiac cells as well)
Do not stop the drug abruptly
Adverse effects ( most frequent occur in CNS)
Nystagmus, ataxia, dysarthria, slurred speech, mentalconfusion, tremor
gingival hyperplasia-
Blood dyscrasias
Rare but fatal : Stevens Johnson syndrome, lupus
Drug interactions: induces P 450 enzyme system
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Phenytoin: Core Patient VariablesPhenytoin: Core Patient Variables Health status
Assess allergies and any cardiac conditions
Life span and gender
Pregnancy category D ( controversial topic )
Antiepileptic drugs increase the metabolism of hormonalcontraceptives, q effectiveness, orisk for unplanned pregnancy
Lifestyle, diet, and habits
Alcohol intake and nutritional status ( assess protein intake)
Absorption q if administered with continuous tube feedings
May increase blood glucose levels.
Be careful driving until effects of drug are known
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Phenytoin: Nursing Diagnoses andOutcomesPhenytoin: Nursing Diagnoses andOutcomes Disturbed Sensory Perception related to adverse effects of
drowsiness and sedation
Desired outcome: the patient will not experience adverse
effects to the degree that sensory perception is alteredenough to impair quality of life.
Altered Oral Mucous Membrane related to the adverse effect ofgingival hyperplasia
Desired outcome: the patient will demonstrate knowledgeof optimal oral hygiene and experience no deterioration indental health.
Risk for Injuryrelated to adverse effects of blood dyscrasias
Desired outcome: the patient will return for follow-up bloodwork while taking phenytoin and will have no life-threateningblood disorders.
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Phenytoin: Planning & InterventionsPhenytoin: Planning & Interventions Maximizing therapeutic effects
Monitor blood levels of the drug.
Titrate the dose upward gradually.
Minimizing adverse effects
Monitor blood levelsnarrow therapeutic range.
Administer IV push phenytoin( during an active seizure)no faster than 50 mg/minute in adults or 1 to 3mg/kg/minute in neonates
Too rapid administration may cause:
hypotension and arrhythmias
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Phenytoin: Teaching, Assessment &EvaluationsPhenytoin: Teaching, Assessment &Evaluations Patient and family education ( p. 339 Box 21-4)
Ensure proper administration of medication.
Take medication with food to decrease GI upset.
Monitor for & notify physician of any adverse effects.
Do notabruptly stop taking this medication
Ongoing assessment and evaluation
Ongoing assessments include:
monitoring patients closely for:
therapeutic responses, seizure control, adverse effects
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Ethosuximide: Core Drug KnowledgeEthosuximide: Core Drug Knowledge Pharmacotherapeutics
Used to treat absence type seizures ( petit mal)
Hypothalmic neurons are responsible for these
Brief LOC ( < 1 minute) : eye blinking, staring
Occur commonly in children ( 100 /day)
Pharmacokinetics
Administered: oral. Metabolism: liver. Excreted:kidneys.
Peak: 3-7 hours. T: 30-60 hours.
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Ethosuximide: Core Drug Knowledge(cont.)Ethosuximide: Core Drug Knowledge(cont.)
Pharmacodynamics inhibits the influx of Ca ions
Contraindications and precautions Hypersensitivity to succinimides
Adverse effects
Drowsiness, dizziness, lethargy, nausea,
blood dyscrasias
Drug interactions
Known to interact with some of the other
antiepileptic drugs
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Ethosuximide: Core Patient VariablesEthosuximide: Core Patient Variables
Health status
Assess allergies, history of renal or hepatic dysfunction
Life span and gender
Pregnancy category C ( but used only for absenceseizures)
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Ethosuximide: Nursing Diagnoses andOutcomesEthosuximide: Nursing Diagnoses andOutcomes
Imbalanced Nutrition: Less than Body Requirements related toadverse GI drug effects of anorexia, abdominal complaints, nausea,and vomiting
Desired outcome: the patient will not experience majornutritional imbalances while receiving ethosuximide.
Risk for Injury from falls related to CNS adverse effects ofethosuximide
Desired outcome: the patient will not sustain an injury while
receiving ethosuximide. Risk for Injury from blood dyscrasias related to adverse effects of
ethosuximide
Desired outcome: the patient will not experience majorchanges in his or her complete blood cell counts.
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Ethosuximide: Planning & InterventionsEthosuximide: Planning & Interventions
Maximizing therapeutic effects
Monitor drug levels at the start of therapy and whenchanging dosage.
Minimizing adverse effects
Assess CBC, UA, and LFT.
Taper dose gradually if needed to discontinue drug.
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Ethosuximide: Teaching, Assessment &EvaluationsEthosuximide: Teaching, Assessment &Evaluations
Patient and family education
Teach patients to take the drug with milk or food ifGI upset occurs.
Notify provider of adverse effects.
Ongoing assessment and evaluation
Ongoing assessments include monitoring patientsclosely for therapeutic responses, seizure control,and adverse effects of drug therapy.
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Antiepileptic Drugs that Increase Effectsof GABAAntiepileptic Drugs that Increase Effectsof GABA
Benzodiazepines ( first line drugs for status epilepticus)
Diazepam Valium ( given PO or IV )highly lipid soluble ( crosses BBB)
highly protein bound ( 98%)
Diazepam onset IV 10- 20 seconds
Duration of action is short
Used as an adjunct therapy
IV injection is slow ( not > 5 mg /minute)
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Drugs Different Than the BenzodiazepinesDrugs Different Than the Benzodiazepines
Phenobarbital ( Luminal Sodium)
CNS depressant suppresses sensory cortexdecreases motor activity
alters cerebellar function
produces drowsiness, sedation and hypnosis
Stimulates GABA receptors : affecting CNS transmitters
Tolerance does not occur to the seizure effects : only thesedative effects
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Drugs Different from the BenzodiazepinesDrugs Different from the BenzodiazepinesPhenobarbital ( Luminal)
Absorbed GI tract
Moderately protein bound (40%)
Long half life
Pregnancy Category D
Induces the P 450 enzyme system
Adverse effects are related to: ( dose dependent)
CNS depression and respiratory depression
Can also produce paradoxical effect in children andolder adults
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