ZONISAMIDE

(zon-i'sa-mide)

Zonegran
Classifications: anticonvulsant; sulfonamide;
Therapeutic: anticonvulsant; sulfonamide
Pregnancy Category: C

Availability

25 mg, 50 mg, 100 mg capsules

Action

A broad-spectrum anticonvulsant that facilitates dopaminergic and serotonergic neurotransmission but does not potentiate the activity of gamma-aminobutyric acid (GABA) in the synapses of the neurons.

Therapeutic Effect

Suppresses focal spike discharges and electroshock seizures. Effective against a variety of seizure types.

Uses

Adjunctive therapy for partial seizures in adults.

Unlabeled Uses

Bipolar disorder.

Contraindications

Hypersensitivity to sulfonamides or zonisamide; pregnancy (category C), lactation; children <16 y.

Cautious Use

Renal or hepatic insufficiency, dehydration, hypovolemia; renal impairment; concomitant administration of drugs that induce or inhibit CYP3A4; older adults.

Route & Dosage

Partial Seizures
Adult: PO Start at 100 mg q.d., may increase after 2 wk to 200 mg/d, may then increase q2wk, if necessary (max: 400 mg/d in 1–2 divided doses)

Administration

Oral

Do not crush or break capsules; ensure capsules are swallowed whole with adequate fluid.
Withdraw drug gradually when discontinued to minimize seizure potential.
Store at 25° C (77° F); room temperature permitted. Protect from light and moisture.

Adverse Effects (≥1%)

Body as a Whole: Flu-like syndrome, weight loss. CNS: Agitation, irritability, anxiety, ataxia, confusion, depression, difficulty concentrating, difficulty with memory, dizziness, fatigue, headache, insomnia, mental slowing, nervousness, nystagmus, paresthesia, schizophrenic behavior, somnolence, tiredness, tremor, convulsion, abnormal gait, hyperesthesia, incoordination. GI: Abdominal pain, anorexia, constipation, diarrhea, dyspepsia, nausea, dry mouth, flatulence, gingivitis, gum hyperplasia, gastritis, stomatitis, cholelithiasis, glossitis, melena, rectal hemorrhage, ulcerative stomatitis, ulcer, dysphagia. Metabolic: Oligohidrosis, sometimes resulting in heat stroke and hyperthermia in children. Respiratory: Rhinitis, pharyngitis, cough. Skin: Ecchymosis, rash, pruritus. Special Senses: Difficulties in verbal expression, diplopia, speech abnormalities, taste perversion, amblyopia, tinnitus. Urogenital: Kidney stones.

Interactions

Drug: Phenytoin, carbamazepine, phenobarbital, valproic acid may decrease half-life of zonisamide.

Pharmacokinetics

Peak: 2–6 h. Distribution: 40% protein bound, extensively binds to erythrocytes. Metabolism: Acetylated in liver by CYP3A4. Elimination: Primarily in urine. Half-Life: 63–105 h.

Nursing Implications

Assessment & Drug Effects

Withhold drug and notify physician if an unexplained rash or S&S of hypersensitivity appear (see Appendix F).
Monitor for and report S&S of CNS impairment (somnolence, excessive fatigue, cognitive deficits, speech or language problems, incoordination, gait disturbances); oligohidrosis (lack of sweating) and hyperthermia in pediatric patients.
Lab tests: Periodic BUN and serum creatinine, and CBC with differential.

Patient & Family Education

Do not abruptly stop taking this medication.
Increase daily fluid intake to minimize risk of renal stones. Notify physician immediately of S&S of renal stones: sudden back or abdominal pain, and blood in urine.
Report any of the following: dizziness, excess drowsiness, frequent headaches, malaise, double vision, lack of coordination, persistent nausea, sore throat, fever, mouth ulcers, or easy bruising.
Exercise special caution with concurrent use of alcohol or CNS depressants.
Do not drive or engage in other potentially hazardous activities until response to drug is known.

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

(133)