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Chapter 14
Antiepileptic Drugs
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Epilepsy
Seizure
Brief episode of abnormal electrical activity in nerve cells of the brain
Convulsion
Involuntary spasmodic contractions of any or all voluntary muscles throughout the body, including skeletal, facial, and ocular muscles
Epilepsy
Chronic, recurrent pattern of seizures
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Epilepsy (Cont.)
Primary (idiopathic)
Cause cannot be determined
Roughly 50% of epilepsy cases
Secondary (symptomatic)
Distinct cause is identified
Trauma, infection, cerebrovascular disorder
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4. Classification of Epilepsy
Generalized onset seizures
Formerly known as grand mal seizures
Tonic-clonic seizures
Absence seizures
Partial onset seizures
Simple (formerly known as petit mal seizures)
Complex
Secondary generalized tonic-clonic
Unclassified seizures
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Status Epilepticus
Multiple seizures occur with no recovery between them
Result: hypotension, hypoxia, brain damage, and death
True medical emergency
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6. Antiepileptic Drugs (AEDs)
Also known as anticonvulsants
Goals of therapy
To control or prevent seizures while maintaining a reasonable quality of life
To minimize adverse effects and drug-induced toxicity
AED therapy is usually lifelong
Combination of drugs may be used
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7. Antiepileptic Drugs (Cont.)
Single-drug therapy is started before multiple-drug therapy is tried.
Serum drug concentrations must be measured.
Therapeutic drug monitoring
Serum concentrations of phenytoin, phenobarbital, carbamazepine, and primidone correlate better with seizure control and toxicity than do those of valproic acid, ethosuximide, and clonazepam.
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8. Antiepileptic Drugs (Cont.)
Antiepileptic drugs traditionally used to manage seizure disorders include:
Barbiturates
Hydantoins
Iminostilbenes plus valproic acid
Second- and third-generation antiepileptics
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9. Mechanism of Action and Drug Effects
Exact mechanism of action is not known.
Pharmacologic effects:
Reduce nerve’s ability to be stimulated
Suppress transmission of impulses from one nerve to the next
Decrease speed of nerve impulse conduction within a neuron
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10. Antiepileptic Drugs: Indications
Prevention or control of seizure activity
Long-term maintenance therapy for chronic, recurring seizures
Acute treatment of convulsions and status epilepticus
Other uses
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11. Antiepileptic Drugs: Adverse Effects
Numerous adverse effects; vary per drug
Adverse effects often necessitate a change in medication
Black box warning as of 2008
Suicidal thoughts and behavior
Long-term therapy with phenytoin (Dilantin) may cause gingival hyperplasia, acne, hirsutism, and Dilantin facies.
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Antiepileptic Drugs
valproic acid
gabapentin (Neurontin)
lamotrigine (Lamictal)
felbamate (Felbatol)
levetiracetam (Keppra)
topiramate (Topamax)
zonisamide (Zonegran)
tiagabine (Gabitril)
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13. Antiepileptic Drugs (Cont.)
pregabalin (Lyrica)
permapanel (Fycompa)
ezogabine (Potiga)
vigabatrin (Sabril)
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14. Barbiturates: Phenobarbital and Primidone (Mysoline)
Primidone is metabolized in the liver to phenobarbital.
Most common adverse effect: sedation
Therapeutic effects: serum drug levels of 10 to 40 mcg/mL
Contraindications: known drug allergy, porphyria, liver or kidney impairment, and respiratory illness
Adverse effects: cardiovascular, CNS, gastrointestinal (GI), and dermatologic reactions
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15. Hydantoins: Phenytoin
Phenytoin (Dilantin) has been used as a first-line drug for many years and is the prototypical drug.
Adverse effects: gingival hyperplasia, acne, hirsutism, Dilantin facies, and osteoporosis
Therapeutic drug levels are usually 10 to 20 mcg/mL.
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16. Hydantoins: Phenytoin (Cont.)
Intravenous (IV) administration
Very irritating to veins
Slow IV directly into a large vein through a large-gauge (20-gauge or larger) venous catheter
Diluted in normal saline (NS) for IV infusion
Filter must be used
Saline flush
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17. Hydantoins: Fosphenytoin (Cerebyx)
Injectable prodrug of phenytoin
Water-soluble phenytoin derivative that can be given intramuscularly or intravenously—by IV push or continuous infusion—without causing burning on injection associated with phenytoin
Adverse effects
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18. Carbamazepine (Tegretol)
Second most commonly prescribed antiepileptic drug in the United States after phenytoin
Autoinduction of hepatic enzymes
Adverse reactions
Drug interactions
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19. Audience Response System Question
A patient in a long-term care facility has a new order for carbamazepine (Tegretol) for seizure management. The nurse monitors for autoinduction, which will result in
toxic levels of carbamazepine (Tegretol).
lower than expected drug levels.
gingival hyperplasia.
cessation of seizure activity.
Correct answer: B
Rationale: Carbamazepine (Tegretol) is associated with autoinduction of hepatic enzymes. Autoinduction is a process in which, over time, a drug stimulates the production of enzymes that enhance its own metabolism, which leads to lower than expected drug concentrations.
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20. Oxcarbazepine (Trileptal)
Chemical analogue of carbamazepine
Precise mechanism of action has not been identified
Adverse reactions
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21. Ethosuximide (Zarontin)
Used in the treatment of uncomplicated absence seizures
Not effective for secondary generalized tonic-clonic seizures
Contraindication: known allergy
Adverse effects: GI and CNS effects
Drug interactions: hepatic enzyme–inducing drugs
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Miscellaneous Drugs
ezogabine (Potiga)
perampanel (Fycompa)
vigabatrin (Sabril)
eslicarbazepine (Aptiom)
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23. Gabapentin (Neurontin)
Chemical analogue of GABA, a neurotransmitter that inhibits brain activity
Believed to work by increasing the synthesis and synaptic accumulation of GABA between neurons
Contraindication: known drug allergy
Adverse effects: CNS and GI symptoms
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24. Lamotrigine (Lamictal)
Also used for the treatment of bipolar disorder
Contraindications: drug allergy
Common adverse effects: relatively minor CNS and GI symptoms and possible Stevens-Johnson syndrome
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25. Levetiracetam (Keppra)
Adjunct therapy for partial seizures with and without secondary generalization
Contraindication: known drug allergy
Mechanism of action: unknown
Adverse effects: generally well tolerated, CNS
No drug interactions
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Pregabalin (Lyrica)
Schedule V controlled substance
Indication: adjunct therapy for partial seizures
Most common uses: neuropathic pain, postherpetic neuralgia, and fibromyalgia
Contraindication: known drug allergy
Adverse drug reactions: primarily CNS related
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27. Audience Response System Question
The nurse is assessing the current medication list of a newly admitted patient. The drug gabapentin (Neurontin) is listed, but the patient states that he does not have any problems with seizures. The nurse suspects that the patient
is unaware of his own disease history.
has been taking his wife’s medication by mistake.
may be taking this drug for neuropathic pain.
is reluctant to admit to having a seizure disorder.
Correct answer: C
Rationale: Gabapentin is commonly used to treat neuropathic pain.
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Nursing Implications
Assessment
Health history, including current medications
Drug allergies
Liver function studies, complete blood count
Baseline vital signs
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29. Audience Response System Question
Before a patient is to receive phenytoin (Dilantin), the nurse practitioner orders lab work. Which lab result is of greatest concern?
High white blood cell count
Low serum albumin levels
Low platelet levels
High hemoglobin levels
Correct answer: B
Rationale: Phenytoin is highly bound to plasma proteins. If serum albumin levels are low, more free drug will be available to exert an effect, and toxicity may occur.
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30. Nursing Implications (Cont.)
Oral drugs
Take regularly, same time each day.
Take with meals to reduce GI upset.
Do not crush, chew, or open extended-release forms.
If patient is NPO for a procedure, contact prescriber regarding AED dosage.
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31. Audience Response System Question
A patient with unstable epilepsy is receiving IV doses of phenytoin (Dilantin). The latest drug level is 12 mcg/mL. Which administration technique will the nurse use?
Administer the drug by rapid IV push.
Infuse slowly, not exceeding 50 mg/min.
Mix the medication with dextrose solution.
Administer via continuous infusion.
Correct answer: B
Rationale: Phenytoin should be mixed only with normal saline, and it should be given by slow IV infusion (but not as a continuous infusion).
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32. Nursing Implications (Cont.)
Intravenous forms
Follow manufacturer’s recommendations for IV delivery—usually given slowly.
Monitor vital signs during administration.
Avoid extravasation of fluids.
Use only normal saline with IV phenytoin (Dilantin).
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33. Nursing Implications (Cont.)
Teach patients to keep a journal to monitor:
Response to AED
Seizure occurrence and descriptions
Adverse effects
Instruct patients to wear a medical alert tag or ID.
AEDs should not be discontinued abruptly.
Follow driving recommendations.
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34. Nursing Implications (Cont.)
Teach patients that therapy is long term and possibly lifelong (not a cure).
Monitor for therapeutic effects:
Decreased or absent seizure activity
Monitor for adverse effects:
Mental status changes, mood changes, changes in level of consciousness or sensorium
Eye problems, visual disorders
Sore throat, fever (blood dyscrasias may occur with hydantoins)
Many others
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35. Audience Response System Question
Which information will the nurse provide to the patient who is receiving antiepileptic drug therapy?
If you feel sleepy when taking the drug, decrease the dose by half.
Take the drug on an empty stomach.
Call your health care provider if you experience a sore throat or fever.
Patients with epilepsy are not able to hold a job and work, so you should apply for benefits.
Correct answer: C
Rationale: To prevent complications, patients should be taught to call the health care provider if they experience fever, sore throat, excessive bleeding or bruising, and new onset of nosebleeds. Drowsiness is a common side effect of these drugs; the dose should never be altered without consulting the prescriber. These medications should be taken with food to decrease GI upset. Most patients with seizure disorders are able to work and are protected by the Americans with Disabilities Act.
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