Zonisamide Side Effects

Brand Names: Zonegran

Please note - some side effects for Zonisamide may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

Side Effects of Zonisamide - for the Consumer

Zonisamide

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Zonisamide:

Abnormal skin sensations; diarrhea; dizziness; drowsiness; flu-like symptoms; headache; irritability; loss of appetite; nausea; stomach upset; tiredness; trouble sleeping; vomiting.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); bone pain; change in the amount of urine produced; confusion; dark or bloody urine; decreased sweating; double vision or other vision problems; fainting; fast breathing; fast, slow, or irregular heartbeat; fever, chills, cough, or sore throat; loss of coordination; memory problems; mouth sores; new or worsening mental or mood changes (eg, depression, agitation, anxiety, panic attacks, aggressiveness, impulsiveness, irritability, hostility, exaggerated feeling of well-being, restlessness, inability to sit still); new or worsening seizures; painful urination; persistent loss of appetite; red, swollen, blistered, or peeling skin; severe muscle pain or weakness; severe or persistent drowsiness; sluggishness; sudden stomach or back pain; suicidal thoughts or actions; swelling of the hands, ankles, or feet; tremor; trouble speaking or other speech problems; trouble thinking or concentrating; unusual bruising or bleeding; unusual eye movements; unusual or disturbing thoughts; unusual tiredness or weakness.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.

Side Effects by Body System - for Healthcare Professionals

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

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.

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.

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

Metabolic side effects have included weight loss (3%) and metabolic acidosis

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.

Hematologic

Hematologic side effects have included ecchymosis (2%).

Respiratory

Respiratory side effects have included rhinitis (2%).

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