Zonisamide | Epilepsy clinician handbook
The usual indication for Zonisamide is focal seizures and secondarily generalised seizures that have not been satisfactorily controlled by other anti-seizure medications.
There is evidence that Zonisamide is an effective broad spectrum anti-seizure medication and has been used in myoclonic seizures, generalised seizures, and syndromes such as Lennox-Gastaut and Myoclonic-astatic epilepsy.
Important: Dosing information
Initiation and escalation doses on this webpage are a guide only.
All medications must be individualised based on:
- patient age, weight, co-morbidities
- disease, seizure type, frequency, duration
- medication metabolism, interactions, side-effect profile characteristics.
Further consultation with appropriate formularies or a paediatric neurologist may be required.
Dosing
Commonly used regime
- Initial dose: 1mg/kg once daily for 2 weeks, then increase as needed and tolerated in steps of 1-2mg/kg/day as tolerated every 2 weeks.
- A reasonable maintenance dose is 6-8mg/kg/day.
- Doses above 500mg generally should not be exceeded.
- Dosages per kilogram can only be used up to weights of 30-40kgs.
- Zonisamide can be taken with food.
- Capsules can be opened and sprinkled onto food or mixed with juice.
- In view of its long half-life, Zonisamide can be administered once or twice daily.
Preparations
- Capsules: 25mg, 50mg, 100mg
Formulary
Side effects
Possible side effects
- Dizziness
- Drowsiness/fatigue
- Psychomotor slowing
- Behavioural changes (aggression/agitation/irritability or psychiatric adverse effects)
- Insomnia
- Double vision
- Weight/appetite loss
- Gastrointestinal disturbance
- Ataxia
Other notable side effects
- Hypersensitivity reaction (fever, rash, lymphadenopathy, haematuria, deranged liver function tests)
- Reduced sweating and heat tolerance
- Metabolic acidosis
- Increased incidence of kidney stones (1-2%)
- Paraesthesia
- Rarely: blood dyscrasia, oligohidrosis, hyperthermia
- All anticonvulsants are potentially teratogenic and this is often dose related
All anti-seizure medications are potentially teratogenic and this is often dose related. For a complete list of adverse effects, appropriate formularies should be consulted.
Interactions and precautions
Precautions
- With increased incidence of renal stones, patients are encouraged to drink liberally.
- If possible, Zonisamide should not be used with Acetazolamide, Topiramate, the Ketogenic Diet, or treatments that may also lead to metabolic acidosis or increased incidence of kidney stones.
- Hepatic impairment: No data. Advised not to use in severe hepatic impairment and use with caution in mild-moderate impairment.
- Renal impairment: Limited data. Slower dose titration may be required.
- Enzyme inducing drugs can increase the clearance of Zonisamide and decrease plasma levels.
- Lower maintenance doses may be needed in some children, especially those not taking enzyme inducing drugs.
Weaning
- If there is an indication of hypersensitivity or a skin reaction, zonisamide should be ceased immediately.
- For other indications, when ceasing Zonisamide it is important to withdraw slowly to minimize the potential of increased seizure frequency.
Pregnancy
- All anti-seizure medications are potentially teratogenic and this is often dose related.
- Usage in pregnancy needs to be discussed with a neurologist.
- There is limited data of the safety of Zonisamide in pregnancy.
Resources
This information is reviewed annually by the Sydney Children’s Hospitals Network Paediatric Epilepsy NSW working group which includes medical, nursing, and pharmacy representation.