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Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter 18
Drugs Treating Seizure Disorders
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
• The following are symptoms of which disorder/disease: loss of consciousness with muscle twitching and mild alterations in consciousness with repetitive blinking?
– A. Epilepsy
– B. Seizures
– C. Parkinson disease
– D. Delirium
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
• B. Seizures
• Rationale: These symptoms are the classic presentation of seizure activity.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Epilepsy • Epilepsy is a brain disorder.
• Seizures are loss of consciousness with generalized muscle twitching or mild alterations in consciousness with repetitive blinking.
• Patients with patterns of seizures who are diagnosed with epilepsy are treated with antiepileptic drugs.
• The three main ways that antiepileptic drugs work are
– Decreasing the rate at which sodium flows into the cell
– Inhibiting calcium flow rate into the cell through specific channels
– Increasing the effect of the neuroinhibitor gamma-aminobutyric acid (GABA)
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Physiology
• Action potentials within neurons are initiated by an influx of sodium into the cell.
• Influx of calcium through specialized voltage-dependent channels also plays a role in creating an action potential.
• When the cell fires, there is a release of neurotransmitters into the synaptic cleft.
• The neurotransmitter glutamate produces excitation.
• GABA normally acts as a counterbalance to glutamate, preventing hyperexcitation.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Physiology of Neurotransmitters
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Pathophysiology • When a group of neurons exhibits coordinated, high-
frequency discharge, it is termed a focus.
• The causes of a focus include head trauma, tumor growth, hypoxia, and inherited birth defects.
• When the activity from a focus spreads to other areas of the brain, causing other neurons to join in the hyperactivity, seizures result.
• Seizures may result from either high levels of glutamate or low levels of GABA.
• Partial seizures occur when focus activity is limited to an area of the brain.
• When the focus activity is within both hemispheres, generalized seizure symptoms occur.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Antiepileptic Drugs that Decrease Sodium Influx
• Control seizures by decreasing sodium influx into the cells.
• Prototype drug: phenytoin (Dilantin)
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Phenytoin: Core Drug Knowledge
• Pharmacotherapeutics
– Used to control partial and generalized seizures
• Pharmacokinetics
– Peak 1.5 to 3 hours. At low doses, the half-life is less than at the therapeutic dose.
• Pharmacodynamics
– The primary site of action is the motor cortex.
– Reversibly binds to sodium channels while they are in the inactive state
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Phenytoin: Core Drug Knowledge (cont.)
• Contraindications and precautions
– Bradycardia and heart block
• Adverse effects
– Nystagmus, ataxia, dysarthria, slurred speech, mental confusion, tremor, and gingival hyperplasia
• Drug interactions
– Numerous drugs interact with phenytoin
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Phenytoin: Core Patient Variables
• Health status
– Assess allergies and any cardiac conditions.
• Life span and gender
– Pregnancy Category D drug
• Lifestyle, diet, and habits
– Alcohol intake and nutritional status
• Environment
– Assess environment where the drug will be given.
– Oral given in any environment
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Phenytoin: Nursing Diagnoses and Outcomes • 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 altered enough to impair quality of life.
• Risk for Injury related to the adverse effects of drowsiness and sedation
– Desired outcome: The patient will not sustain any injury while taking phenytoin.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Phenytoin: Nursing Diagnoses and Outcomes (cont.)
• Altered Oral Mucous Membrane related to the adverse effect of gingival hyperplasia
– Desired outcome: The patient will demonstrate knowledge of optimal oral hygiene and experience no deterioration in dental health.
• Risk for Injury related to adverse effects of blood dyscrasias
– Desired outcome: The patient will return for follow-up blood work while taking phenytoin and will have no life-threatening blood disorders.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Phenytoin: Planning and Interventions
• Maximizing therapeutic effects
– Monitor blood levels of the drug.
– Titrate the dose upward gradually.
• Minimizing adverse effects
– Monitor blood levels—narrow therapeutic range.
– Administer IV push phenytoin no faster than 50 mg/minute in adults or 1 to 3 mg/kg/minute in neonates.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Phenytoin: Teaching, Assessment, and Evaluations
• Patient and family education
– Ensure proper administration of medication.
– Take medication with food to decrease GI upset.
– Notify the physician of adverse effects.
• Ongoing assessment and evaluation
– Ongoing assessments include monitoring patients closely for therapeutic responses, seizure control, and adverse effects to drug therapy.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
• What condition places the patient at greater risk for toxicity to phenytoin?
– A. Alcoholism
– B. Sinus bradycardia
– C. Obesity
– D. Malnutrition
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
• D. Malnutrition
• Rationale: Malnutrition causes a greater amount of free, active drug in the blood because less protein albumin is available for binding.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Antiepileptic Drugs that Decrease Calcium Influx
• Prototype drug: ethosuximide (Zarontin)
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Ethosuximide: Core Drug Knowledge
• Pharmacotherapeutics
– Used to treat absence (petit mal) seizures
• Pharmacokinetics
– Administered: oral. Metabolism: liver. Excreted: kidneys. Peak: 3 to 7 hours. T½: 30 to 60 hours.
• Pharmacodynamics
– Inhibiting the influx of calcium ions
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Ethosuximide: Core Drug Knowledge (cont.)
• Contraindications and precautions
– Hypersensitivity
• Adverse effects
– Drowsiness, dizziness, lethargy, nausea, and blood dyscrasias
• Drug interactions
– Known to interact with some of the other antiepileptic drugs
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Ethosuximide: Core Patient Variables
• Health status
– Assess allergies, history of renal or hepatic dysfunction.
• Life span and gender
– Pregnancy Category C drug
• Environment
– Assess environment where the drug will be given.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Ethosuximide: Nursing Diagnoses and Outcomes
• Imbalanced nutrition: Less than Body Requirements related to adverse GI drug effects of anorexia, abdominal complaints, nausea, and vomiting
– Desired outcome: The patient will not experience major nutritional imbalances while receiving ethosuximide.
• Risk for Injury from falls related to CNS adverse effects of ethosuximide
– Desired outcome: The patient will not sustain an injury while receiving ethosuximide.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Ethosuximide: Nursing Diagnoses and Outcomes (cont.)
• Risk for Injury from blood dyscrasias related to adverse effects of ethosuximide
– Desired outcome: The patient will not experience major changes in his or her complete blood cell counts.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Ethosuximide: Planning and Interventions
• Maximizing therapeutic effects
– Monitor drug levels at the start of therapy and when changing dosage.
• Minimizing adverse effects
– Assess CBC, UA, and LFT.
– Taper dose gradually if need to discontinue the drug.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Ethosuximide: Teaching, Assessment, and Evaluations
• Patient and family education
– Teach patients to take the drug with milk or food if GI upset occurs.
– Notify the provider of adverse effects.
• Ongoing assessment and evaluation
– Ongoing assessments include monitoring patients closely for therapeutic responses, seizure control, and adverse effects of drug therapy.
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
• Ethosuximide is used to treat __________ seizures.
– A. Absence
– B. Grand mal
– C. Generalized
– D. Febrile
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
• A. Absence
• Rationale: Ethosuximide is used to treat absence (petit mal) seizures.