Action

Unknown. Thought to prevent seizures by inhibiting nerve impulses in hippocampus of brain. Chemically unrelated to other anticonvulsants.

Availability

Oral solution: 100 mg/ml

Solution for injection: 500 mg/5 ml in single-use 5-ml vial

Tablets: 250 mg, 500 mg, 750 mg, 1,000 mg

Tablets (extended-release): 500 mg

Indications and dosages

➣ Adjunctive treatment of partial-onset seizures in patients with epilepsy

Adults and children ages 16 and older: Initially, 500 mg P.O. (immediate-release preparations) b.i.d. May increase by 1,000 mg/day q 2 weeks to a maximum daily dosage of 3,000 mg, as needed. Or, initially 1,000 mg P.O. (extended-release tablets) once daily. Adjust in increments of 1,000 mg q 2 weeks to a maximum daily dosage of 3,000 mg, as appropriate. Or, when oral administration is temporarily not feasible, give initial daily I.V. dosage equivalent to total daily dosage and frequency of oral drug.

Children ages 4 to 15: Initially, 20 mg/kg/day P.O. (immediate-release preparations) in two divided doses (10 mg/kg b.i.d.). Increase daily dosage every 2 weeks by increments of 20 mg/kg to recommended daily dosage of 60 mg/kg (30 mg/kg b.i.d.). If patient can't tolerate daily dosage of 60 mg/kg, reduce daily dosage.

➣ Myoclonic seizures in patients with juvenile myoclonic epilepsy

Children ages 16 and older: Initially, 500 mg I.V. b.i.d. Increase dosage by 1,000 mg/day every 2 weeks to recommended total daily dosage of 3,000 mg.

Children ages 12 and older: Initially, 500 mg P.O. (immediate-release tablets or oral solution) b.i.d. Increase dosage by 1,000 mg/day every 2 weeks to the recommended total daily dose of 3,000 mg.

➣ Primary generalized tonic-clonic seizures

Adults and children ages 16 and older: Initially, 1,000 mg P.O. b.i.d. Increase dosage by 1,000 mg/day every 2 weeks to the recommended total daily dose of 3,000 mg.

Children ages 6 to 15: Initially, 10 mg/kg P.O. b.i.d. Increase daily dosage every 2 weeks by increments of 20 mg/kg to recommended total daily dosage of 60 mg/kg (30 mg/kg b.i.d.).

Dosage adjustment

• Renal impairment (especially in dialysis patients)

Contraindications

• Hypersensitivity to drug or its components

Precautions

Use cautiously in:

• renal, hepatic, or cardiac impairment

• psychosis

• pregnant or breastfeeding patients

• children younger than age 16 (safety and efficacy not established).

Administration

• Give oral form with or without food.

• Know that patients weighing 44 lb (20 kg) or less should be given oral solution.

• Be aware that injection form is intended for temporary use when oral route isn't feasible.

See Be aware that injection form is for I.V. use only and must be diluted before administering.

• Dilute 500 mg/ml in 100 ml 0.9% normal saline injection, lactated Ringer's injection, or dextrose 5% injection. Withdraw 5 ml, 10 ml, or 15 ml for 500-mg, 1,000-mg, or 1,500-mg dose, respectively.

• Administer as a 15-minute I.V. infusion.

See Don't discontinue suddenly. Instead, taper dosage gradually.

Adverse reactions

CNS: aggression, anger, irritability, mental or mood changes, asthenia, ataxia, dizziness, drowsiness, somnolence, fatigue, nervousness, depression, anxiety, amnesia, hostility, coordination difficulties, headache, paresthesia, vertigo

EENT: diplopia, pharyngitis, rhinitis, sinusitis

GI: nausea, vomiting, anorexia

Hematologic: neutropenia, leukopenia

Respiratory: cough

Other: infection, pain

Interactions

Drug-herbs. Evening primrose oil: lowered seizure threshold

Patient monitoring

• Measure temperature and watch for signs and symptoms of infection.

See Monitor neurologic status. Report signs that patient is dangerous to himself or others.

• Evaluate nutritional status. Report signs of anorexia.

Patient teaching

• Tell patient to take with or without food.

• Instruct patient to swallow extended-release tablets whole and not to chew, break, or crush them.

See Advise family to contact prescriber if patient poses a danger to himself or others.

See Caution patient not to stop taking drug abruptly, because doing so may increase seizure activity.

• Teach patient and family about adverse CNS reactions, and tell them to report these promptly. Urge them to take safety measures to prevent injury.

• Instruct patient to avoid activities that require mental alertness until CNS reactions are known.

• Inform patient that he'll undergo periodic blood testing during therapy.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the herbs mentioned above.