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Zonisamide Side Effects

Medically reviewed by Last updated on Apr 27, 2022.

For the Consumer

Applies to zonisamide: oral capsule

Side effects requiring immediate medical attention

Along with its needed effects, zonisamide may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking zonisamide:

More common

  • Discouragement
  • double vision
  • feeling sad or empty
  • irritability
  • lack of appetite
  • loss of interest or pleasure
  • mood or mental changes
  • shakiness or unsteady walking
  • tiredness
  • trouble with concentrating
  • trouble with sleeping

Less common

  • Agitation
  • bruising
  • delusions
  • hallucinations
  • large, flat blue or purplish patches on the skin
  • rash

Incidence not known

  • Blurred vision
  • change in near or distance vision
  • difficulty in focusing eyes
  • eye pain
  • increase in frequency of seizures
  • swelling of the face
  • yellow eyes or skin

Side effects not requiring immediate medical attention

Some side effects of zonisamide may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  • Abdominal or stomach pain
  • anxiety
  • diarrhea
  • difficulty with memory
  • dizziness
  • double vision
  • headache
  • loss of appetite
  • nausea
  • restlessness
  • sleepiness
  • unusual drowsiness
  • unusual tiredness or weakness

Less common

  • Aching muscles or joints
  • acid or sour stomach
  • bad, unusual, or unpleasant taste in the mouth
  • belching
  • change in taste
  • chills
  • constipation
  • difficulty with speaking
  • difficulty with thinking
  • dry mouth
  • fever
  • general ill feeling
  • headache
  • heartburn
  • indigestion
  • mental slowness
  • nervousness
  • runny or stuffy nose
  • sneezing
  • tingling, burning, or prickly feelings on the skin
  • uncontrolled, back and forth, or rolling eye movements
  • weight loss

For Healthcare Professionals

Applies to zonisamide: oral capsule


The most common adverse reactions to this drug are somnolence, dizziness, and anorexia.[Ref]


Very common (10% or more): Anorexia (13%)

Common (1% to 10%): Abdominal pain, nausea, diarrhea, dyspepsia, constipation, dry mouth[Ref]

Nervous system

Very common (10% or more): Somnolence (17%), dizziness (13%), headache (10%), ataxia

Common (1% to 10%): Paresthesia, fatigue, tiredness, bradyphrenia, tremor

Uncommon (0.1% to 1%): Convulsion

Very rare (less than 0.01%): Coma, grand mal seizure, myasthenic syndrome, neuroleptic malignant syndrome, status epilepticus

Postmarketing reports: Restless legs syndrome[Ref]


Common (1% to 10%): Speech abnormalities, difficulties in verbal expression, taste perversion[Ref]


Very common (10% or more): Agitation, irritability, confusional state, depression

Common (1% to 10%): Difficulty concentrating, difficulty with memory, mental slowing, insomnia, anxiety, nervousness, affect lability, psychotic disorder

Uncommon (0.1% to 1%): Anger, aggression, suicidal ideation, suicide attempt

Very rare (less than 0.01%): Hallucination, amnesia, mania[Ref]


Common (1% to 10%): Nystagmus, diplopia[Ref]


Common (1% to 10%): Rash

Very rare (less than 0.01%): Drug rash with eosinophilia and systemic symptoms, anhidrosis, erythema multiforme, pruritus, Stevens-Johnson syndrome, toxic epidermal necrolysis[Ref]


Very common (10% or more): Anorexia

Common (1% to 10%): Weight loss

Very rare (less than 0.01%): Metabolic acidosis

Postmarketing reports: Elevated creatine phosphokinase[Ref]


Common (1% to 10%): Ecchymosis

Very rare (less than 0.01%): Agranulocytosis, aplastic anemia, leukocytosis, leucopenia, lymphadenopathy, pancytopenia, thrombocytopenia[Ref]


Common (1% to 10%): Rhinitis

Uncommon (0.1% to 1%): Pneumonia[Ref]


Uncommon (0.1% to 1%): Urinary tract infection

Postmarketing reports: Acute pancreatitis[Ref]


Postmarketing reports: Rhabdomyolysis[Ref]


Uncommon (0.1% to 1%): Urinary tract infection[Ref]


Common (1% to 10%): Hypersensitivity

Very rare (less than 0.01%): Drug induced hypersensitivity syndrome[Ref]


Common (1% to 10%): Influenza syndrome[Ref]


Very rare (less than 0.01%): Renal tubular acidosis

Frequency not reported: Nephrolithiasis, hydronephrosis, renal failure, urine abnormality[Ref]


1. "Product Information. Zonegran (zonisamide)." Elan Pharmaceuticals (2001):

2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

3. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online." (2006):

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.