chapter21 drugs treating seizure disorders

8/7/2019 Chapter21 Drugs treating seizure disorders

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Copyright 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins

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

chapter21 drugs treating seizure disorders

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