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Zonisade Side Effects

Generic name: zonisamide

Medically reviewed by Last updated on Jul 4, 2023.

Note: This document contains side effect information about zonisamide. Some dosage forms listed on this page may not apply to the brand name Zonisade.

Applies to zonisamide: oral capsule, oral suspension.

Serious side effects of Zonisade

Along with its needed effects, zonisamide (the active ingredient contained in Zonisade) 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

  • Blindness
  • blurred vision
  • decreased vision
  • discouragement
  • double vision
  • eye pain
  • fast, irregular, pounding, or racing heartbeat or pulse
  • feeling sad or empty
  • headache
  • irritability
  • lack of appetite
  • loss of interest or pleasure
  • mood or mental changes
  • shakiness or unsteady walking
  • tearing
  • tiredness
  • trouble concentrating
  • trouble sleeping

Less common

  • Agitation
  • black, tarry stools
  • bruising
  • changes in skin color
  • chest pain
  • chills
  • confusion
  • cough
  • delusions
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • fever
  • hallucinations
  • large, flat blue or purplish patches on the skin
  • nervousness
  • pain, tenderness, or swelling of the foot or leg
  • painful or difficult urination
  • pale skin
  • pounding in the ears
  • rash
  • slow or fast heartbeat
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • sweating
  • swollen glands
  • unusual bleeding or bruising
  • unusual tiredness or weakness


  • Anxiety
  • chest tightness
  • clay-colored stools
  • coma
  • dark urine
  • decreased urine output
  • diarrhea
  • dilated neck veins
  • indigestion
  • irregular breathing
  • irregular heartbeat
  • small, red or purple spots on the skin
  • stiff neck
  • stomach pain and cramps
  • swelling of the face, fingers, feet, or lower legs
  • trouble breathing
  • twitching, twisting, uncontrolled repetitive movements of the tongue, lips, face, arms, or legs
  • unpleasant breath odor
  • vomiting of blood
  • watery or bloody diarrhea
  • weight gain
  • yellow eyes or skin

Incidence not known

  • Change in near or distance vision
  • difficulty in focusing eyes
  • increase in frequency of seizures
  • swelling of the face

Other side effects of Zonisade

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

  • Continuing ringing or buzzing or other unexplained noise in ears
  • diarrhea
  • difficulty with memory
  • dizziness
  • hearing loss
  • loss of appetite
  • nausea
  • restlessness
  • sleepiness
  • unusual drowsiness

Less common

  • Acid or sour stomach
  • bad, unusual, or unpleasant taste in the mouth
  • belching
  • bleeding gums
  • change in taste
  • constipation
  • decreased interest in sexual intercourse
  • difficulty with speaking
  • difficulty with thinking
  • dry mouth
  • general ill feeling
  • headache
  • heartburn
  • inability to have or keep an erection
  • increased hair growth, especially on the face
  • irritation in the mouth
  • loss in sexual ability, desire, drive, or performance
  • loss of strength or energy
  • mental slowness
  • mouth ulcers
  • muscle or joint pain
  • redness and swelling of the gums
  • 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, oral suspension.


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.

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.