zonisamide: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
zonisamide: clinical details
Prescribing considerations
- Confirm that the intended indication and age group match the licence: monotherapy is licensed for newly diagnosed adults; paediatric use is adjunctive from age 6 years.
- Avoid abrupt withdrawal because of breakthrough-seizure risk.
- Assess renal and hepatic impairment, previous renal stones, glaucoma or other eye disease, low body weight, acidosis risk, hydration and heat exposure.
- Discuss reproductive risks, effective contraception and pregnancy planning where relevant.
- Zonisamide is a category 2 anti-seizure medicine for manufacturer switching: base continuity decisions on clinical judgement and discussion with the patient or carer.
Contraindications and cautions
- Hypersensitivity to zonisamide, sulphonamides or formulation excipients.
- For Desizon suspension, hypersensitivity to its parahydroxybenzoate preservatives is also contraindicated.
Monitoring
- Monitor seizure control, adherence, adverse effects and mental state.
- Assess renal function if clinically indicated; discontinue under specialist direction if acute renal failure or a sustained clinically significant creatinine rise develops.
- Consider serum bicarbonate evaluation in people with acidosis risk factors or compatible symptoms.
- Monitor appetite, weight, hydration and sweating; in children, monitor weight, growth and development.
- Evaluate liver function if hepatic dysfunction is suspected.
- Investigate rash, visual symptoms, renal-stone symptoms, unexplained lethargy or confusion, blood-disorder symptoms, or severe muscle symptoms promptly.
Clinical pharmacology
Zonisamide modulates voltage-sensitive sodium and calcium channels and GABA-mediated inhibition, with weak carbonic anhydrase inhibition. It is well absorbed orally, partly metabolised through CYP3A4 and eliminated mainly through the urine; its long elimination half-life means effects and interactions may persist.
Formulation and product differences
- Hard capsules are oral formulations that may be taken with or without food.
- Desizon is a strawberry-flavoured oral suspension supplied with an oral syringe. It must be shaken thoroughly before preparation and supports administration with water, orange juice, yoghurt or specified feeding tubes.
- The suspension contains parahydroxybenzoate preservatives and traces of sugars and sulphur dioxide, creating formulation-specific allergy and intolerance considerations.
zonisamide preparations and strengths
Capsule
Route: Oral
Strengths: 25 mg, 50 mg, 100 mg
Oral suspension
Route: Oral
Strengths: 20 mg/mL
zonisamide interactions
Tell the prescriber or pharmacist about all prescribed, non-prescribed and complementary products. Important examples include:
Topiramate or acetazolamide
Combined carbonic anhydrase inhibition may increase concerns about metabolic acidosis, kidney stones and heat-related effects; paediatric co-administration is not recommended in the product information.
Phenytoin, carbamazepine or phenobarbital
These enzyme-inducing anti-seizure medicines can reduce zonisamide exposure, and changes to either treatment may alter seizure control or adverse effects.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.