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.
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.
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