Introduction to Clinical Pharmacology Chapter 29 Antiepileptics

Drugs Used for Managing Seizure Disorders Antiepileptics The drug categories used as antiepileptics are the hydantoins, carboxylic acid derivatives, succinimides, oxazolidinediones, benzodiazepines, and non-specified drugs.

Antiepileptics: Actions #1 Hydantoins stabilize the hyperexcitability postsynaptically in the motor cortex of the brain. Carboxylic acid derivatives increase levels of gamma (γ)-aminobutyric acid (GABA), which stabilizes cell membranes. Succinimides depress the motor cortex, creating a higher threshold before nerves react to the convulsive stimuli.

Antiepileptics: Actions #2 Oxazolidinediones decrease repetitive synaptic transmissions of nerve impulses. Benzodiazepines elevate the seizure threshold by decreasing postsynaptic excitation. Non-specified drugs have differing properties; for example, gabapentin is a GABA agonist, and topiramate blocks the seizure activity rather than raising the threshold.

Antiepileptics: Uses Used prophylactically to prevent seizures following trauma, neurosurgery, or tumor Used in treatment of: Seizures of all types; neuropathic pain; bipolar disorders; anxiety disorders

Antiepileptics: Adverse Reactions Central nervous system reactions: drowsiness; weakness; dizziness; headache; somnolence; nystagmus; ataxia; slurred speech Gastrointestinal reactions: nausea; vomiting; anorexia; constipation; diarrhea; gingival hyperplasia, acute liver failure with felbamate Other: skin rashes; pruritus; urticaria; urinary frequency; serious skin reactions; hematologic changes

Antiepileptics: Contraindications #1 Contraindicated in patients hypersensitive to the drugs Phenytoin is contraindicated in patients with sinus bradycardia; with sinoatrial block; with Adams–Stokes syndrome; with second- and third-degree atrioventricular (AV) block; during pregnancy and lactation Ethotoin (Peganone) is contraindicated in patients with hepatic abnormalities

Antiepileptics: Contraindications #2 Succinimides are contraindicated in patients with bone marrow depression or hepatic or renal impairment Carbamazepine is contraindicated in patients with bone marrow depression or hepatic or renal impairment and during pregnancy Valproic acid (Depakote) is not administered to patients with renal impairment or during pregnancy Oxcarbazepine may exacerbate dementia

Antiepileptics: Precautions #1 Used cautiously in patients with liver or kidney disease and neurologic disorders The newer medications such as elicarbazepine and oxcarbazepine can cause hyponatremia. Benzodiazepines are used cautiously during pregnancy and in patients with psychoses; patients with acute narrow-angle glaucoma; elderly or debilitated patients

Antiepileptics: Precautions #2 Phenytoin is used cautiously in patients with hypotension; severe myocardial insufficiency; hepatic impairment Trimethadione is used with caution in patients with eye disorders Miscellaneous antiepileptics are used cautiously in patients with glaucoma or increased intraocular pressure; a history of cardiac, renal, or liver dysfunction; and psychiatric disorders

Antiepileptics: Interactions #1 Interacting drug Effect of interaction Antibiotics/antifungals Increased effect of anticonvulsant Tricyclic antidepressants Salicylates Cimetidine Theophylline Decreased serum levels of anticonvulsant

Antiepileptics: Interactions #2 Interacting drug Effect of interaction Antiseizure medications May increase seizure activity Protease inhibitors Increased carbamazepine levels resulting in toxicity Oral contraceptives Decreased effectiveness of birth control, resulting in breakthrough bleeding or pregnancy Analgesics or alcohol Increased depressant effect Antidiabetic medications Increased blood glucose levels

Nursing Process: Assessment #1 Preadministration assessment: Obtain vital signs at the time of the initial assessment to provide baseline data Thorough patient history is necessary to identify type of seizure disorder Primary health care provider may order laboratory and diagnostic tests

Nursing Process: Assessment #2 Ongoing assessment: Carefully document each seizure with regard to time of occurrence; duration of seizure; psychic or motor activity occurring before, during, after seizure Dosage adjustments are based on patient’s response to therapy, as well as occurrence of adverse reactions Serum plasma levels of anticonvulsant are measured regularly to monitor for toxicity

Nursing Diagnoses Risk for Injury related to seizure disorder, drowsiness, ataxia, and vision disturbances Risk for Impaired Skin Integrity related to adverse reactions (rash) Risk for Infection related to immunosuppression secondary to drug therapy Impaired Oral Mucous Membranes related to gum overgrowth secondary to hydantoins

Nursing Process: Planning Expected outcomes for patient depend on the type and severity of the seizure but may include: Optimal response to therapy Support of patient needs related to management of adverse reactions Understanding of and compliance with prescribed therapeutic regimen

Nursing Process: Implementation #1 Promoting an optimal response to therapy: Make notation on the care plan and inform all health care team members of the importance of the drug Barbiturates: Monitor patient carefully during administration of barbiturate, taking blood pressure and observing respirations frequently

Nursing Process: Implementation #2 Promoting an optimal response to therapy (cont.) Benzodiazepines: Dosage of benzodiazepines is highly individualized; increase the dosage cautiously to avoid adverse reactions, particularly in elderly and debilitated patients Do not mix diazepam with other drugs

Nursing Process: Implementation #3 Promoting an optimal response to therapy (cont.) Hydantoins: Monitor serum concentrations of drug on regular basis to detect signs of toxicity Oxazolidinediones: Used when less toxic drugs are not effective in controlling seizure disorder

Nursing Process: Implementation #4 Promoting an optimal response to therapy (cont.) Succinimides: Effective in controlling partial seizures; these drugs are given with food to prevent GI upset Miscellaneous antiepileptics: Drug is absorbed rapidly when taken orally, should not be chewed but swallowed whole

Nursing Process: Implementation #5 Monitoring and managing patient needs: Risk for injury: Assist the patient with all ambulatory activities Use caution when giving an oral preparation as aspiration of tablet, capsule, or liquid may occur if patient experiences drowsiness Test swallowing ability of patient by offering small sips of water before giving drug

Nursing Process: Implementation #6 Monitoring and managing patients needs (cont.) Risk for impaired skin integrity: Carefully examine all affected areas and provide an accurate description Be alert for signs of pancytopenia, such as sore throat, fever, general malaise, bleeding of the mucous membranes, epistaxis, easy bruising Routine laboratory tests, such as complete blood counts and differential counts, should be performed periodically

Nursing Process: Implementation #7 Monitoring and managing patient needs (cont.) Impaired oral mucous membranes: Periodically inspect mouth, teeth, gums of patients in a hospital or long-term clinical setting

Nursing Process: Implementation #8 Educating the patient and family: When patient receives diagnosis of epilepsy, nurse must assist patient and family to adjust to diagnosis Instruct family members in care of patient before, during, and after seizures Explain importance of restricting some activities until seizures are controlled by drugs Assist patient to look for other modes of transportation in order to continue typical activities or employment Review adverse drug reactions associated with the prescribed anticonvulsant with the patient and family members

Nursing Process: Implementation #9 Educating the patient and family (cont.) Hydantoins: Inform dentist and other primary health care providers of use of this drug Brush and floss teeth after each meal and make periodic dental appointments for oral examination and care

Nursing Process: Implementation #10 Educating the patient and family (cont.) Take medication with food to reduce GI upset Thoroughly shake phenytoin suspension immediately before use Do not take capsules that are discolored

Nursing Process: Implementation #11 Educating the patient and family (cont.) Notify primary health care provider if any of the following occurs: skin rash; bleeding; swollen or tender gums; yellowish discoloration of the skin or eyes; unexplained fever; sore throat; unusual bleeding or bruising; persistent headache; malaise; or pregnancy

Nursing Process: Implementation #12 Educating the patient and family (cont.) Succinimides: If GI upset occurs, take drug with food or milk Notify primary health care provider if any of the following occurs: skin rash; joint pain; unexplained fever; sore throat; usual bleeding or bruising; drowsiness; dizziness; blurred vision; or pregnancy

Nursing Process: Implementation #13 Educating the patient and family (cont.) Oxazolidinediones: Determine protective measures when exposed to ultraviolet light, sunlight Notify primary health care provider if following reactions occur: visual disturbances; excessive drowsiness; dizziness; sore throat; fever; skin rash; pregnancy; malaise; easy bruising; epistaxis; bleeding tendencies

Nursing Process: Evaluation Therapeutic effect is achieved and convulsions are controlled No injury is evident Adverse reactions are identified, reported, and managed successfully through appropriate nursing interventions Patient verbalizes the importance of complying with the prescribed treatment regimen Patient verbalizes an understanding of treatment modalities and the importance of continued follow-up care Patient and family demonstrate an understanding of the drug regimen

Question #1 Is the following statement true or false? Convulsion and seizure are terms often used interchangeably to describe sudden, involuntary muscle contractions due to changes in brain electrical activity.

Answer to Question #1 True Convulsion and seizure are terms often used interchangeably to describe sudden, involuntary muscle contractions due to changes in brain electrical activity. Seizures may be caused by disease, injury, or metabolic changes or inherited at birth.

Question #2 Is the following statement true or false? Anticonvulsant drugs are used to depress the abnormal nerve impulses discharged in the brain.

Answer to Question #2 True Anticonvulsant drugs are used to depress the abnormal nerve impulses discharged in the brain. When discontinued, the drugs should be tapered down or seizure activity may return.