Chapter 19 Antiseizure Drugs Copyright © 2018, Elsevier Inc. All rights reserved. Epilepsy Seizure disorder Abnormal electric discharges from cerebral neurons Characteristics • Loss of consciousness • Involuntary, uncontrolled movements Cause • Unknown • Secondary to brain trauma or anoxia, infection, stroke • Isolated seizures due to fever, electrolyte, or acid–base imbalance, alcohol, or drugs Copyright © 2018, Elsevier Inc. All rights reserved. 2 International Classification of Seizures Common generalized seizure types Tonic–clonic (grand mal) • Most common • Generalized alternating muscle spasms and jerkiness Absence (petit mal) • Brief loss of consciousness (10 seconds or less) • Usually occurs in children Copyright © 2018, Elsevier Inc. All rights reserved. 3 International Classification of Seizures (Cont.) Common partial seizure type Psychomotor • Repetitive behavior Chewing or swallowing motions • Behavioral changes • Motor seizures Copyright © 2018, Elsevier Inc. All rights reserved. 4 Antiseizure Drugs Antiseizure drugs Stabilize nerve cell membranes Suppress abnormal electric impulses in cerebral cortex Specific types of action Suppress sodium influx Suppress calcium influx Enhance action of GABA Promote GABA release Copyright © 2018, Elsevier Inc. All rights reserved. 5 Hydantoins Phenytoin Contraindications • Pregnancy (teratogenic) Therapeutic serum level • 10 to 20 mcg/mL Side effect/adverse reactions • Gingival hyperplasia, nystagmus, diplopia • Headache, dizziness, slurred speech, alopecia • Purple glove syndrome, ventricular fibrillation • Depression, suicidal ideation • Hyperglycemia, GI distress, urine discoloration • Thrombocytopenia, leukopenia • Stevens-Johnson syndrome Copyright © 2018, Elsevier Inc. All rights reserved. 6 Hydantoins (Cont.) Phenytoin Drug interactions • Increased effects with cimetidine, isoniazid, chloramphenicol, sulfonamides • Decreased effects with folic acid, antacids, calcium, sucralfate, antineoplastics, antipsychotics, primrose, ginkgo, borage • Decreased effects of anticoagulants, oral contraceptives, antihistamines, corticosteroids, theophylline, dopamine, cyclosporine, quinidine, rifampin Copyright © 2018, Elsevier Inc. All rights reserved. 7 Nursing Process: Phenytoin Assessment Obtain a current health history including drugs and herbs used. Determine renal and hepatic function lab values. Nursing diagnosis Injury, risk for Falls, risk for Planning Patient’s seizure frequency will diminish. Copyright © 2018, Elsevier Inc. All rights reserved. 8 Nursing Process: Phenytoin (Cont.) Nursing interventions Monitor serum drug levels of antiseizure drug to determine therapeutic range. Warn female patients taking oral contraceptives and antiseizure drugs to use additional contraceptive method. Use seizure precautions for patients at risk for seizures. Advise patients not to drive or perform other hazardous activities when initiating drug therapy. Evaluation Copyright © 2018, Elsevier Inc. All rights reserved. 9 Barbiturates Phenobarbital Action • Enhances GABA activity Use • Tonic–clonic, partial, myoclonic seizures, status epilepticus Therapeutic serum range • 20 to 40 mcg/mL Side effects • Sedation, tolerance Discontinuation • Should be gradual Copyright © 2018, Elsevier Inc. All rights reserved. 10 Succinimide Ethosuximide Action • Decreases calcium influx Use • Absence seizures Therapeutic serum range • 40 to 100 mcg/mL Adverse effects • Blood dyscrasias, renal and liver impairment • Systemic lupus erythematosus. Copyright © 2018, Elsevier Inc. All rights reserved. 11 Benzodiazepines Clonazepam Clorazepate dipotassium Treats absence and myoclonic seizures Tolerance may occur in 6 months Treats partial seizures Diazepam Treats status epilepticus Must be administered IV for status epilepticus Short-term effect • Other antiseizure drugs must be given during or immediately after administration of diazepam Copyright © 2018, Elsevier Inc. All rights reserved. 12 Iminostilbene Carbamazepine Use Tonic–clonic, partial seizures Also used for psychiatric disorders (e.g., bipolar disorder), trigeminal neuralgia, and alcohol withdrawal Therapeutic serum range 4 to 12 mcg/mL Copyright © 2018, Elsevier Inc. All rights reserved. 13 Iminostilbene (Cont.) Carbamazepine Side effects, adverse reactions Dizziness, drowsiness, headache, blurred vision GI distress, ataxia, weakness, anemia Agranulocytosis, Stevens-Johnson syndrome Possible interaction with grapefruit juice Copyright © 2018, Elsevier Inc. All rights reserved. 14 Valproate Valproic acid Therapeutic serum range Use—tonic–clonic, absence, and mixed seizures 50 to 100 mcg/mL Side effects, adverse reactions Dizziness, drowsiness Insomnia, diplopia Weakness, GI distress Suicidal ideation Thrombocytopenia Copyright © 2018, Elsevier Inc. All rights reserved. 15 Antiseizure Drugs and Pregnancy Seizure episodes increase 25% in women with epilepsy who are pregnant Many antiseizure drugs are teratogenic Antiseizure drugs tend to inhibit vitamin K Contributes to infant hemorrhage soon after birth Vitamin K may be given during last few days of pregnancy or given to infant soon after birth Antiseizure drugs increase loss of folate (folic acid) in pregnant patients Pregnant females need daily folate supplements Copyright © 2018, Elsevier Inc. All rights reserved. 16 Antiseizure Drugs and Febrile Seizures Seizures associated with fever Usually occur in children between the ages of 3 months and 5 years Epilepsy develops in approximately 2.5% of children who have had one or more febrile seizures. Prophylactic treatment for high-risk patients Phenobarbital or diazepam Copyright © 2018, Elsevier Inc. All rights reserved. 17 Antiseizure Drugs and Status Epilepticus Status epilepticus Medical emergency Treatment must begin immediately Treatment Diazepam Lorazepam Followed by phenytoin IV For continued seizures: midazolam, propofol Slow IV administration to avoid respiratory depression Copyright © 2018, Elsevier Inc. All rights reserved. 18 Practice Question #1 What is the highest priority nursing diagnosis for a patient taking phenytoin? A. B. C. D. Anxiety Risk for falls Risk for constipation Deficient fluid volume Copyright © 2018, Elsevier Inc. All rights reserved. 19 Practice Question #2 Before administering a daily dose of phenytoin, it is most important for the nurse to A. B. C. D. maintain the patient on bed rest. check phenytoin levels. monitor intake and output. monitor renal function tests. Copyright © 2018, Elsevier Inc. All rights reserved. 20 Practice Question #3 A patient was discharged 3 days ago on phenytoin therapy for seizure disorder. The patient comes to the emergency department experiencing seizures. What will be of most value to determine the etiology of the returned seizures? A. B. C. D. A CT scan An EEG Serum phenytoin levels Serum electrolytes Copyright © 2018, Elsevier Inc. All rights reserved. 21 Practice Question #4 When assessing a patient taking hydantoin therapy for seizure disorder, which indicates an adverse reaction to this therapy? A. B. C. D. Thrombocytopenia Leukocytosis Gingival atrophy Hypoglycemia Copyright © 2018, Elsevier Inc. All rights reserved. 22 Practice Question #5 A patient is experiencing status epilepticus. The nurse anticipates immediate administration of which drug? A. B. C. D. Phenobarbital Phenytoin Valproic acid Diazepam Copyright © 2018, Elsevier Inc. All rights reserved. 23
