Zonisamide

A to Z Drug Facts

 Action Unknown; however, may produce anticonvulsant effects through action at sodium and calcium channels.

 Indications Adjunctive therapy in the treatment of partial seizures in adult epileptic patients.

 Contraindications Hypersensitivity to sulfonamides or zonisamide.

 Route/Dosage

Adults (over 16 yr): PO 100 mg/day initially, then the dose may be increased by 100 mg/day at intervals of at least 2 wk (max, 600 mg/day).

 Interactions

Drugs that induce liver enzymes (eg, carbamazepine, phenobarbital, phenytoin): May increase the metabolism and decrease the half-life of zonisamide.

 Lab Test Interferences None well documented.

 Adverse Reactions

CARDIOVASCULAR: Vascular insufficiency; atrial fibrillation; heart failure; ventricular extrasystoles. CNS: Somnolence; dizziness; headache; agitation; irritability; fatigue; tiredness; difficulty concentrating; memory difficulty; mental slowing; ataxia; paresthesia; confusion; depression; insomnia; anxiety; nervousness; schizophrenic/schizophreniform behavior; speech abnormalities; difficult verbal expression; tremor; convulsion; abnormal gait; hyperesthesia; incoordination. DERMATOLOGIC: Rash; pruritus. EENT: Nystagmus; diplopia; taste perversion; amblyopia; tinnitus. GI: Nausea; anorexia; vomiting; abdominal pain; diarrhea; dyspepsia; constipation; dry mouth. HEMATOLOGIC: Ecchymosis; leukopenia; anemia; lymphadenopathy; thrombocytopenia; microcytic anemia. HEPATIC: Increased ALT and AST. METABOLIC: Weight loss. RESPIRATORY: Rhinitis; pulmonary embolus; pharyngitis; increased cough. OTHER: Flu syndrome; asthenia.

 Precautions

Pregnancy: Category C. Lactation: Undetermined. Children: Safety and efficacy in children younger than 16 yr not established. Elderly: Select dose with caution, reflecting the greater frequency of decreased hepatic, renal, or cardiac function and comorbidity. Cognitive adverse events: Frequent CNS adverse events, including depression, psychosis, psychomotor slowing, somnolence, fatigue, and difficulty with concentration, speech, or language problems have occurred. Hypersensitivity reactions: May present as fatal or severe reactions such as Stevens-Johnson syndrome, toxic epidermal necrolysis; fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias. Oligohydrosis and hyperthermia in pediatrics: Oligohydrosis, sometimes resulting in heat stroke and hospitalization, has been reported in pediatric patients. Renal function impairment: Do not use if glomerular filtration rate is less than 50 mL/min. Serious skin reactions: Consider discontinuing drug. Sudden death: Sudden unexplained death has occurred. Withdrawal seizures: Abrupt withdrawal may precipitate increased seizure frequency or status epilepticus; gradually discontinue or decrease dose.

 Administration/Storage

• Administer once or twice daily.
• May be administered without regard to meals.
• Administer capsules whole. Do not chew or break the capsule.
• Dose is gradually increased at 2-wk intervals.
• Do not administer to patient with Ccr less than 50 mL/min.
• Store capsules at controlled room temperature. Protect from moisture and light.

 Assessment/Interventions

• Obtain patient history, including drug history, and any known allergies. Note history of sulfonamide allergy, renal, or hepatic impairment.
• Ensure that patient has reviewed the Patient Information Leaflet before starting therapy.
• Ensure that baseline renal function studies are performed before starting therapy and periodically during therapy.
• Have patient increase fluid intake (6 to 8 glasses water/day) to reduce risk of kidney stones.
• Monitor patient for seizure activity. Report seizure activity to health care provider.
• Monitor patient for skin rash, fever, hives, sores in the mouth, unusual bruising, or lack of sweating. Notify health care provider immediately if noted.
• Monitor patient for GI, CNS, psychiatric, and general body side effects. Report to health care provider if noted and significant.
• Implement safety precautions for patients who experience dizziness or ataxia.

 Patient/Family Education

• Explain name, dose, action, and potential side effects of drug.
• Instruct patient to take exactly as prescribed and to not change the dose or discontinue unless advised to do so by their health care provider.
• Advise patient that dose is gradually increased no more often than every 2 wk.
• Advise patient to swallow capsule whole. Do not chew, crush, or break tablet.
• Advise patient that each dose may be taken without regard to meals.
• Warn patient that if they miss a dose to not double up on the next dose.
• Advise patient to increase fluid intake (6 to 8 glasses of water/day) while taking this medication to reduce the risk of kidney stones from forming.
• Advise patient that if medication needs to be discontinued it will be slowly withdrawn over a period of 2 wk or more unless safety concerns (eg, rash) require a more rapid withdrawal.
• Caution patient that drug may cause drowsiness and to use caution while driving or performing other tasks requiring mental alertness until tolerance is determined.
• Advise women to contact their health care provider if pregnant, plan on becoming pregnant, or breastfeeding.
• Instruct patient to contact their health care provider immediately if they develop a skin rash, sudden back pain, abdominal pain, or blood in urine, fever, sore throat, oral ulcers, easy bruising, depression, unusual thoughts, speech or language problems, or decreased sweating or rise in body temperature.
• Instruct parent or caregiver to contact health care provider immediately if a child taking zonisamide is not sweating as usual with or without a fever.
• Instruct patient to inform health care provider if seizures become worse or if new types of seizures occur.
• Advise patient to inform health care provider if they experience symptoms of depression.
• Advise patient to avoid taking any prescription or OTC medications or dietary supplements unless advised to do so by their health care provider.
• Advise patient that laboratory tests and follow-up visits will be required to monitor therapy and keep appointments.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts