zonisamide at a glance
Medicine class
Anti-seizure medicine with weak carbonic anhydrase activity.
Licensed use
Focal seizures, with or without progression to bilateral convulsive seizures.
Food
Capsules and oral suspension may be taken with or without food.
Stopping treatment
Do not stop suddenly; withdrawal should be planned gradually by the prescriber.
What is zonisamide used for?
The selected products are licensed for:
Treatment used alone for focal seizures, with or without secondary generalisation, in adults with newly diagnosed epilepsy.
Treatment added to other anti-seizure medicines for focal seizures, with or without secondary generalisation, in adults, adolescents and children aged 6 years and over.
How does zonisamide work?
Its mechanism is not fully understood. Zonisamide appears to block voltage-sensitive sodium and calcium channels, reducing synchronised electrical firing and the spread of seizure activity. It may also enhance inhibitory signalling involving GABA.
zonisamide preparations and strengths
Capsule
Route: Oral
Strengths: 25 mg, 50 mg, 100 mg
Oral suspension
Route: Oral
Strengths: 20 mg/mL
How to take zonisamide
Follow the product-specific instructions and the prescriber's directions.
Either formulation may be taken with or without food.
For the oral suspension, shake the bottle vigorously for 30 seconds and prepare it immediately using the supplied oral syringe.
The suspension may be swallowed from the syringe followed by water, diluted in water or orange juice, or mixed with yoghurt. Do not mix it with carbonated drinks.
The suspension can be given through specified feeding tubes; follow the product instructions for preparation and tube rinsing.
zonisamide side effects
Common or expected effects
- Sleepiness, dizziness or fatigue
- Reduced appetite or weight loss
- Memory, attention, speech, balance or coordination difficulties
- Agitation, irritability, low mood or confusion
- Nausea, indigestion, abdominal discomfort, constipation or diarrhoea
- Double vision
- Rash or itching
Get urgent medical advice
- Severe allergy or a blistering, peeling or rapidly spreading rash
- Overheating, high temperature or reduced sweating, particularly in children
- Eye pain, redness or sudden blurred or reduced vision
- Kidney-stone symptoms, such as severe side or back pain or blood in the urine
- Possible metabolic acidosis: unusual drowsiness, headache, breathlessness or loss of appetite
- Possible blood disorder: fever, sore throat, swollen glands, unusual bruising or marked tiredness
- Severe muscle pain or weakness, which may indicate muscle breakdown
- New suicidal thoughts or major behavioural or mental-state changes
zonisamide in pregnancy
Pregnancy data are limited, so potential fetal and neurodevelopmental risks remain uncertain. Product information also notes signals for lower birth weight, preterm birth and babies being small for gestational age. Zonisamide may still be used when a specialist judges that seizure-control benefits outweigh possible risks. Seek specialist review when planning pregnancy or promptly after an unplanned pregnancy, and do not stop treatment suddenly.
zonisamide while breastfeeding
Zonisamide passes into breast milk at concentrations similar to those in maternal blood and remains in the body for a long time. Product information advises a specialist-led decision between breastfeeding and continuing zonisamide; discuss feeding plans before birth where possible.
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.
Common questions about zonisamide
Answers are fully visible for fast scanning and source review.
Is zonisamide a sulphonamide?
Yes. It contains a sulphonamide group, and a history of allergy to sulphonamide medicines is a contraindication in the selected product information.
Should zonisamide be stopped suddenly?
No. Sudden withdrawal can trigger breakthrough seizures; any discontinuation should be planned gradually by the treating clinician.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.