Zonisamide Side Effects

Some side effects of zonisamide may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to zonisamide: oral capsule

Get emergency medical help if you have any of these signs of an allergic reaction while taking zonisamide: any form of skin rash; hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Report any new or worsening symptoms to your doctor, such as: mood or behavior changes, anxiety, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, hyperactive (mentally or physically), more depressed, or have thoughts about suicide or hurting yourself.

Call your doctor at once if you have a serious side effect such as:

• increased or worsening seizures;

• pale skin, feeling light-headed or short of breath, rapid heart rate, trouble concentrating;

• fever, chills, body aches, flu symptoms, sores in your mouth and throat;

• severe pain in your lower back, blood in your urine;

• loss of appetite, tired feeling, problems with thinking or speech, trouble concentrating;

• feeling very thirsty or hot, being unable to urinate, heavy sweating, or hot and dry skin without sweating;

• the first sign of any skin rash, no matter how mild; or

• severe skin reaction -- fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain, followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.

Less serious side effects of zonisamide may include:

• drowsiness;

• dizziness; or

• loss of balance or coordination.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to zonisamide: oral capsule

General

General side effects have included somnolence (17%), headache (10%), fatigue (8%), tiredness (7%), abdominal pain (6%), and flu syndrome (4%).

Gastrointestinal

Gastrointestinal side effects have included anorexia (13%), nausea (9%), diarrhea (5%), dyspepsia (3%), constipation (2%), and dry mouth (2%).

Nervous system

Nervous system side effects have included dizziness (13%), ataxia (6%), nystagmus (4%), and paresthesia (4%). A case of restless legs syndrome has also been reported.

Other

Patients (especially pediatric patients) treated with zonisamide should be monitored closely for evidence of decreased sweating and increased body temperature, especially in warm or hot weather.

Reports have shown pediatric patients to be at an increased risk for zonisamide-associated oligohidrosis and hyperthermia.

Other side effects have included speech abnormalities (5%), difficulties in verbal expression (2%), taste perversion (2%), and visual hallucinations.

Psychiatric

Two cases of zonisamide induced behavior disorders have been reported in children with plasma levels within or below the therapeutic range. A case of zonisamide induced mania has been reported.

Psychiatric side effects have included agitation/irritability (9%), confusion (6%), difficulty concentrating (6%), difficulty with memory (6%), depression (6%), insomnia (6%), mental slowing (4%), anxiety (3%), nervousness (2%), and schizophrenic/schizophreniform behavior (2%). A case of zonisamide-induced mania has also been reported.

Ocular

Ocular side effects have included diplopia (6%).

Dermatologic

Dermatologic side effects have included rash (3%). A case of toxic epidermal necrolysis has also been reported.

Metabolic

Zonisamide can cause metabolic acidosis, characterized by hyperchloremia and decreased serum bicarbonate. Metabolic acidosis is often asymptomatic.

Generally, zonisamide-induced metabolic acidosis occurs early in treatment, but may occur at any time during treatment.

The risk of development of zonisamide-induced metabolic acidosis appears to be greater at higher doses of zonisamide, but can occur with doses as low as 25 mg daily.

Conditions or therapies that may predispose patients to acidosis include renal disease, severe respiratory disorders, diarrhea, surgery, ketogenic diet, or other drugs (e.g. acetazolamide)

Signs and symptoms of persistent metabolic acidosis may include hyperventilation, fatigue and anorexia. More severe symptoms may include cardiac arrhythmias and stupor.

Chronic, untreated metabolic acidosis may increase the risk for kidney stones, nephrocalcinosis, and bone abnormalities (e.g., osteoporosis, osteomalacia, and rickets in pediatric patients) with an increased risk for fractures.

A pretreatment (baseline) and periodic measurements of serum bicarbonate are recommended during zonisamide treatment. In addition, if signs or symptoms of metabolic acidosis are observed, serum bicarbonate should be measured.

Metabolic side effects have included weight loss (3%), metabolic acidosis and postmarketing reports of elevated creatine phosphokinase.

Hematologic

Hematologic side effects have included ecchymosis (2%).

Respiratory

Respiratory side effects have included rhinitis (2%).

Endocrine

Endocrine side effects have included postmarketing reports of acute pancreatitis.

Musculoskeletal

Musculoskeletal side effects have included postmarketing reports of rhabdomyolysis.

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