Pharmacologic class: Sulfonamide

Therapeutic class: Anticonvulsant

Pregnancy risk category C


Raises seizure threshold and reduces seizure duration, probably by stabilizing neuronal membranes through action on sodium and calcium channels


Capsules: 25 mg, 50 mg, 100 mg

Indications and dosages

Adjunctive treatment of partial seizures

Adults and children older than age 16: Initially, 100 mg P.O. daily for 2 weeks, then, if required, increased to 200 mg P.O. daily for at least 2 weeks. May increase in 100-mg increments at 2-week intervals to 300 to 400 mg daily as required. Daily dosage ranges from 100 to 600 mg.

Dosage adjustment

• Hepatic or renal impairment

• Elderly patients

Off-label uses

• Infantile spasms

• Progressive myoclonic epilepsy

• Weight loss


• Hypersensitivity to drug or other sulfonamides


Use cautiously in:

• hepatic or renal disease

• pregnant or breastfeeding patients

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


• Give with or without food.

Adverse reactions

CNS: drowsiness, fatigue, agitation, irritability, depression, dizziness, psychomotor slowing, psychosis, asthenia, abnormal gait, incoordination, tremor, ataxia, headache, confusion, impaired memory, hyperesthesia, paresthesia, seizures

EENT: diplopia, amblyopia, nystagmus, tinnitus, rhinitis, pharyngitis

GI: nausea, vomiting, diarrhea, dyspepsia, dry mouth, anorexia, pancreatitis

GU: renal calculi

Hematologic: anemia, leukopenia

Respiratory: cough

Skin: rash, pruritus, bruising, Stevens-Johnson syndrome

Other: abnormal taste, weight loss, allergic reactions, oligohidrosis and hyperthermia (in children), flulike symptoms, accidental injury


Drug-drug. Carbamazepine, phenobarbital, phenytoin, valproic acid: decreased zonisamide blood level and effects

CYP450-3A4 inducers: decreased zonisamide half-life

CYP450-3A4 inhibitors: increased zonisamide blood level

Drug-diagnostic tests. Blood urea nitrogen, creatine kinase, creatinine: increased levels

Platelets, white blood cells: decreased counts

Patient monitoring

• Monitor CBC with white cell differential.

• Assess neurologic status; report significant adverse reactions.

• Monitor renal function tests. Watch for signs and symptoms of renal calculi.

Monitor for rash, which may be first sign of Stevens-Johnson syndrome. If rash occurs, discontinue drug and notify prescriber immediately.

Patient teaching

• Explain therapy to patient. Instruct him to keep seizure diary and show it to prescriber.

• Instruct patient to swallow capsules whole. Advise him to drink 6 to 8 glasses of water daily to help prevent kidney stones.

Warn patient that stopping drug abruptly may cause status epilepticus.

• Caution patient to avoid driving and other hazardous activities until he knows how drug affects him and until seizures are well controlled.

Tell patient to immediately report rash, fever, sore throat, sudden back pain, depression, speech or language problems, or painful urination.

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

McGraw-Hill Nurse's Drug Handbook, 7th Ed. Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved


(zoe-niss-a-mide) ,


(trade name)


Therapeutic: anticonvulsants
Pharmacologic: sulfonamides
Pregnancy Category: C


Partial seizures in adults.


Raises the threshold for seizures and reduces duration of seizures probably by action on sodium and calcium channels.

Therapeutic effects

Decreased frequency of partial seizures.


Absorption: Well absorbed following oral administration.
Distribution: Binds extensively to red blood cells.
Protein Binding: 40%.
Metabolism and Excretion: Mostly metabolized by the liver; 35% excreted unchanged in urine. Some metabolism occurs via CYP3A4 enzyme system.
Half-life: 63 hr (plasma).

Time/action profile (blood levels†)

POunknown2–6 hr24 hr
†Requires 2 weeks of dosing to achieve steady-state blood levels


Contraindicated in: Hypersensitivity to zonisamide or sulfonamides.
Use Cautiously in: All patients (may ↑ risk of suicidal thoughts/behaviors);Hepatic or renal disease (may require slower titration/more frequent monitoring; ↑ risk of metabolic acidosis with renal impairment);Patients with respiratory disorders, diarrhea, or undergoing surgery (↑ risk of metabolic acidosis); Obstetric / Lactation: Use only if potential benefit justifies risk to fetus/infant; Pediatric: Children ≤16 yr (safety not established; ↑ risk of oligohydrosis, hyperthermia, and/or metabolic acidosis).

Adverse Reactions/Side Effects

Central nervous system

  • suicidal thoughts (life-threatening)
  • drowsiness (most frequent)
  • fatigue (most frequent)
  • agitation/irritability
  • depression
  • dizziness
  • psychomotor slowing
  • psychosis
  • weakness

Ear, Eye, Nose, Throat

  • amblyopia
  • tinnitus


  • cough
  • pharyngitis


  • anorexia
  • nausea
  • vomiting

Fluid and Electrolyte

  • metabolic acidosis


  • kidney stones


  • stevens-johnson syndrome (life-threatening)
  • oligohydrosis (↑ in children)
  • rash


  • hyperthermia (↑ in children)


  • abnormal gait
  • hyperasthesia
  • incoordination
  • tremor


Drug-Drug interaction

Drugs that induce or inhibit CYP3A4 may alter blood levels and effects of zonisamide.Blood levels and effects may be ↓ by phenytoin, carbamazepine, phenobarbital, or valproate.May enhance the adverse/toxic effect of carbonic anhydrase inhibitors, avoid combination.


Oral (Adults and Children >16 yr) 100 mg once daily initially for 2 wk, then ↑ to 200 mg daily for 2 wk; with subsequent increments of 100 mg made at 2-wk intervals as required (range 100–600 mg/day). Can be given as a single daily dose or in 2 divided doses.
Oral (Infants and Children) Initial: 1–2 mg/kg/day given in two divided doses/day; increase dose in increments of 0.5–1 mg/kg/day every 2 weeks (maximum dose: 12 mg/kg/day).

Availability (generic available)

Capsules: 25 mg, 50 mg, 100 mg Cost: Generic — 25 mg $54.80 / 100, 50 mg $109.60 / 100, 100 mg $219.20 / 100

Nursing implications

Nursing assessment

  • Monitor closely for notable changes in behavior that could indicate the emergence or worsening of suicidal thoughts or behavior or depression.
  • Monitor frequency, duration, and characteristics of seizures.
  • Monitor patient frequently for development of skin rash. Unexplained rash may require discontinuation of therapy.
  • Assess patient for allergy to sulfa drugs.
  • Lab Test Considerations: Monitor renal function periodically during therapy. May cause ↑ creatinine and BUN.
    • Measure serum bicarbonate before starting and periodically during therapy. Metabolic acidosis may be more frequent and severe in younger patients.
    • May cause ↑ in serum alkaline phosphatase.

Potential Nursing Diagnoses

Risk for injury (Adverse Reactions)


  • Oral: May be administered with or without meals. Capsules should be swallowed whole.

Patient/Family Teaching

  • Instruct patient to take zonisamide as directed, even if feeling well. Consult health care professional if a dose is missed. Do not discontinue abruptly without consulting health care professional; may cause seizures. Instruct patient to read the Medication Guide before starting and with each Rx refill, changes may occur.
  • Instruct patient to contact health care professional immediately if skin rash occurs or seizures worsen. Patient should also contact health care professional if a child taking zonisamide is not sweating as usual, with or without a fever, or if they develop fever, sore throat, oral ulcers, easy bruising, depression, unusual thoughts, speech or language problems.
  • May cause drowsiness. Caution patient to avoid driving or other activities requiring alertness until cleared by health care professional and effects of medication is known.
  • Advise patient to increase fluid intake to at least 6–8 glasses of water/day to minimize risk of kidney stones. Instruct patient to contact health care professional if symptoms of kidney stones (sudden back pain, abdominal pain, blood in urine) occur.
  • Advise patient and family to notify health care professional if thoughts about suicide or dying, attempts to commit suicide; new or worse depression; new or worse anxiety; feeling very agitated or restless; panic attacks; trouble sleeping; new or worse irritability; acting aggressive; being angry or violent; acting on dangerous impulses; an extreme increase in activity and talking, other unusual changes in behavior or mood occur.
  • Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications.
  • May have teratogenic effects. Advise women of childbearing age to use effective contraception throughout therapy. Instruct patient to notify health care professional if pregnancy is planned or suspected or if planning to breast feed.

Evaluation/Desired Outcomes

  • Decrease in frequency and duration of partial seizures.
Drug Guide, © 2015 Farlex and Partners


Zonisamide Neurology An agent used to manage partial seizures in adults with epilepsy. See Seizures.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.
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