OXCARBAZEPINE

OXCARBAZEPINE (ox-car'ba-ze-peen) Trileptal Classifications: anticonvulsant; Therapeutic: anticonvulsant Prototype: Carbamazepine Pregnancy Category: C

Availability

150 mg, 300 mg, 600 mg tablets; 300 mg/5 mL suspension

Action

Anticonvulsant properties may result from blockage of voltage-sensitive sodium channels, which results in stabilization of hyperexcited neural membranes.

Therapeutic Effect

Inhibits repetitive neuronal firing, and decreased propagation of neuronal impulses.

Uses

Monotherapy or adjunctive therapy in the treatment of partial seizures in adults and children age 4–16 y.

Contraindications

Hypersensitivity to oxcarbazepine; pregnancy (category C); children <3 y.

Cautious Use

Older adults; renal impairment; renal failure; children <8 y; infertility, hyponatremia, SIADH, and drugs associated with SIADH as an adverse effect; lactation.

Route & Dosage

Partial Seizures Adult: PO Start with 300 mg b.i.d. and increase by 600 mg/d qwk to 2400 mg/d in 2 divided doses for monotherapy or 1200 mg/d as adjunctive therapy Child: PO 4–16 y, Initiate with 8–10 mg/kg/d divided b.i.d. (max: 600 mg/d), gradually increase weekly to target dose (divided b.i.d.) based on weight: 20–29 kg, 900 mg/d; 29.1–39 kg, 1200 mg/d; >39 kg, 1800 mg/d Renal Impairment Clcr <30 mL/min: initiate at ? usual starting dose (300 mg b.i.d.)

Administration

Oral

• Initiate therapy at one-half the usual starting dose (300 mg/d) if creatinine clearance <30 mL/min.
• Do not abruptly stop this medication; withdraw drug gradually when discontinued to minimize seizure potential.
• Store preferably at 25° C (77° F), but room temperature permitted. Keep container tightly closed.

Adverse Effects (≥1%)

Body as a Whole: Fatigue, asthenia, peripheral edema, generalized edema, chest pain, weight gain. CV: Hypotension. GI: Nausea, vomiting, abdominal pain, diarrhea, dyspepsia, constipation, gastritis, anorexia, dry mouth. Hematologic: Lymphadenopathy. Metabolic: Hyponatremia. Musculoskeletal: Muscle weakness. CNS: Headache, dizziness, somnolence, ataxia, nystagmus, abnormal gait, insomnia, tremor, nervousness, agitation, abnormal coordination, speech disorder, confusion, abnormal thinking, aggravate convulsions, emotional lability. Respiratory: Rhinitis, cough, bronchitis, pharyngitis. Skin: Acne, hot flushes, purpura, Stevens-Johnson syndrome, toxic epidermal necrolysis. Special Senses: Diplopia, vertigo, abnormal vision, abnormal accommodation, taste perversion, ear ache. Urogenital: Urinary tract infection, micturition frequency, vaginitis.

Interactions

Drug: Carbamazepine, phenobarbital, phenytoin, valproic acid, verapamil, calcium channel blockers may decrease oxcarbazepine levels; may increase levels of phenobarbital, phenytoin; may decrease levels of felodipine, oral contraceptives. Herbal: Ginkgo may decrease anticonvulsant effectiveness. Evening primrose oil may decrease the seizure threshold.

Pharmacokinetics

Absorption: Rapidly and completely from GI tract. Peak: Steady-state levels reached in 2–3 d. Distribution: 40% protein bound. Metabolism: Extensively metabolized in liver to active 10-monohydroxy metabolite (MHD). Elimination: 95% in kidneys. Half-Life: 2 h, MHD 9 h.

Nursing Implications

Assessment & Drug Effects

• Monitor for and report S&S of: Hyponatremia (e.g., nausea, malaise, headache, lethargy, confusion); CNS impairment (e.g., somnolence, excessive fatigue, cognitive deficits, speech or language problems, incoordination, gait disturbances).
• Monitor phenytoin levels when administered concurrently.
• Lab tests: Periodic serum sodium, T₄ level; when oxcarbazepine is used as adjunctive therapy, closely monitor plasma level of the concomitant antiepileptic drug during titration of the oxcarbazepine dose.

Patient & Family Education

• Notify physician of the following: Dizziness, excess drowsiness, frequent headaches, malaise, double vision, lack of coordination, or persistent nausea.
• Exercise special caution with concurrent use of alcohol or CNS depressants.
• Use caution with potentially hazardous activities and driving until response to drug is known.
• Use or add barrier contraceptive since drug may render hormonal methods ineffective.

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Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug