Chapter 19 Antiseizure Drugs 1 Epilepsy Seizure disorder Abnormal electric discharges from cerebral neurons Characteristics • Loss of consciousness • Involuntary, uncontrolled movements Cause • Disruption in electrical brain functioning • Secondary to brain trauma or anoxia, infection, stroke • Isolated seizures due to fever, stress, hypoglycemic reaction, electrolyte, or acid–base imbalance, alcohol, or drugs 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 Common partial seizure type Psychomotor • Repetitive behavior Chewing or swallowing motions • Behavioral changes • Motor seizures 3 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 4 Phenytoin Action Inhibits sodium influx Stabilizes cell membrane Reduces repetitive neuronal firing Limits seizures Side effect/adverse reactions Gingival hyperplasia, nystagmus, ataxia Headache, dizziness, drowsiness, hypotension Insomnia, confusion, depression, paresthesia Purple glove syndrome, suicidal ideation Hyperglycemia, GI distress, constipation Bradycardia, tachycardia, ventricular fibrillation 5 Phenytoin (cont) Drug interactions Increased effects with cimetidine, sulfonamides Decreased effects with antacids, calcium, sucralfate, antineoplastics, primrose, ginkgo, borage Increased effects of anticoagulants, aspirin Contraindications Pregnancy (teratogenic) Therapeutic serum level 10 to 20 mcg/mL 6 7 Barbiturates Phenobarbital Action • Enhances GABA activity Use • Tonic–clonic, partial, myoclonic seizures, status epilepticus Therapeutic serum range • 15 to 40 mcg/mL Side effects • Sedation, tolerance Discontinuation • Should be gradual 8 Succinimides Ethosuximide Action • Decreases calcium influx Use • Absence seizures Therapeutic serum range • 40 to 100 mcg/mL Adverse effects • Blood dyscrasias • Systemic lupus erythematosus • Psychosis, suicidal ideation 9 Benzodiazepines Clonazepam Clorazepate Treats absence and myoclonic seizures Tolerance may occur in 6 months Treats partial seizures Diazepam Treats status epilepticus Administered IV for status epilepticus Short-term effect • Other antiseizure drugs must be given during or immediately after administration of diazepam 10 Iminostilbene Carbamazepine Use • Tonic–clonic, partial seizures • Also used for psychiatric disorders (e.g., bipolar disorder), trigeminal neuralgia Therapeutic serum range • 4 to 12 mcg/mL 11 Valproate Valproic acid Therapeutic serum range Use tonic–clonic, absence, and partial seizures 50 to 100 mcg/mL Side effects, adverse reactions Dizziness, drowsiness, weakness, insomnia Insomnia, diplopia, GI distress Suicidal ideation, thrombocytopenia 12 Antiseizure Drugs and Pregnancy One-third of females with seizure disorder are at greater risk in pregnancy 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 Need daily folate supplements 13 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 14 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 15 Honorable Mentions Gabapentin (Reduces Excitability of nerve cells) Pregabalin (Decreases electrical activity) Topiramate (Decreases electrical activity) Lamotrigine (Interferes with sodium channels) 16 Clinical Judgment: Phenytoin Concept Recognize cues Obtain a current health history including drugs and herbs used. Determine renal and hepatic function lab values. Analyze cues and prioritize hypothesis Intracranial regulation Injury, falls, need for patient teaching Generate solutions Patient’s seizure frequency will diminish. 17 Clinical Judgment: Phenytoin (Cont) Take action 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. Evaluate outcomes 18 Practice Question #1 Before administering a daily dose of phenytoin, what it is most important for the nurse to do? A. B. C. D. Maintain the patient on bed rest. Check phenytoin levels. Monitor intake and output. Monitor renal function tests. 19 Practice Question #2 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 20 Practice Question #3 When assessing a patient taking phenytoin therapy for seizure disorder, which indicates an adverse reaction to this therapy? A. B. C. D. Thrombocytopenia Leukocytosis Gingival atrophy Hypoglycemia 21 Practice Question #4 A patient is experiencing status epilepticus. The nurse anticipates immediate administration of which drug? A. B. C. D. Phenobarbital Phenytoin Valproic acid Diazepam 22
