Formulary
Zonisamide: Indications, Dosing, Side Effects and Interactions
Zonisamide clinical drug profile including indications, dosing, side effects, cautions and interactions.
MedNext Academy | 4 min read
Zonisamide: Indications, Dosing, Side Effects and Interactions
Zonisamide clinical drug profile including indications, dosing, side effects, cautions and interactions.
Indications and dose
**Monotherapy**
- **Adult** (By Mouth): for treatment of focal seizures with or without secondary generalisation in adults with newly diagnosed epilepsy Initially 100 mg once daily for 2 weeks, then increased in steps of 100 mg every 2 weeks, usual maintenance dose 300 mg once daily; maximum 500 mg per day.
**Adjunctive treatment**
- **Child** (By Mouth): 6-17 years (body-weight 55 kg and above) Initially 1 mg/kg once daily for 7 days, then increased in steps of 1 mg/kg every 7 days, usual maintenance 300-500 mg once daily, dose to be increased at 2-week intervals in patients who are not receiving concomitant carbamazepine, phenytoin, phenobarbital or other potent inducers of cytochrome P450 enzyme CYP3A4.
- **Adult** (By Mouth): Initially 50 mg daily in 2 divided doses for 7 days, then increased to 100 mg daily in 2 divided doses, then increased in steps of 100 mg every 7 days, usual maintenance 300-500 mg daily in 1-2 divided doses, dose to be increased at 2-week intervals in patients who are not receiving concomitant carbamazepine, phenytoin, phenobarbital or other potent inducers of cytochrome P450 enzyme CYP3A4.
**Adjunctive treatment for refractory focal seizures with or without secondary generalisation for zonisamide**
- **Child 6-17 years (body-weight 20-54 kg)** (By mouth): Initially 1 mg/kg once daily for 7 days, then increased in steps of 1 mg/kg every 7 days, usual maintenance 6-8 mg/kg once daily (max. per dose 500 mg once daily), dose to be increased at 2-week intervals in patients who are not receiving concomitant carbamazepine, phenytoin, phenobarbital or other potent inducers of cytochrome P450 enzyme CYP3A4.
- **Child 6-17 years (body-weight 55 kg and above)** (By mouth): Initially 1 mg/kg once daily for 7 days, then increased in steps of 1 mg/kg every 7 days, usual maintenance 300-500 mg once daily, dose to be increased at 2-week intervals in patients who are not receiving concomitant carbamazepine, phenytoin, phenobarbital or other potent inducers of cytochrome P450 enzyme CYP3A4.
Cautions
Elderly (in adults); history of eye disorders; low body-weight or poor appetite-monitor weight throughout treatment (fatal cases of weight loss reported in children); metabolic acidosis-monitor serum bicarbonate concentration in children and those with other risk factors (consider dose reduction or discontinuation if metabolic acidosis develops); risk factors for renal stone formation (particularly predisposition to nephrolithiasis) Cautions, further information Avoid overheating and ensure adequate hydration especially in children, during strenuous activity or if in warm environment (fatal cases of heat stroke reported in children). M
Side effects
Common or very common Alopecia; anxiety; appetite decreased; ataxia; bradyphrenia; concentration impaired; confusion; constipation; depression; diarrhoea; dizziness; drowsiness; fatigue; fever; gastrointestinal discomfort; hypersensitivity; influenza like illness; insomnia; memory loss; mood altered; nausea; nystagmus; paraesthesia; peripheral oedema; psychosis; rash (consider discontinuation); skin reactions; speech disorder; tremor; urolithiases; vision disorders; vomiting; weight decreased Uncommon Behaviour abnormal; gallbladder disorders; hallucination; hypokalaemia; increased risk of infection; leucopenia; respiratory disorder; seizures; suicidal behaviours; thrombocytopenia Rare or very rare Agranulocytosis; alveolitis allergic; angle closure glaucoma; anhidrosis; bone marrow disorders; coma; dyspnoea; eye pain; heat stroke; hepatocellular injury; hydronephrosis; leucocytosis; lymphadenopathy; metabolic acidosis; myasthenic syndrome; neuroleptic malignant syndrome; pancreatitis; renal failure; renal tubular acidosis; rhabdomyolysis; severe cutaneous adverse reactions (SCARs); urine abnormal Frequency not known Sudden unexplained death in epilepsy
Interactions
**Other interactions (13):**
- Effect of Zonisamide Aristo on cytochrome P450 enzymes In vitro studies using human liver microsomes show no or little (<25%) inhibition of cytochrome P450 isozymes 1A2, 2A6, 2B6, 2C8, 2C9, 2C19,...
- Potential for Zonisamide Aristo to affect other medicinal products Anti-epileptic medicinal products In epileptic patients, steady-state dosing with Zonisamide Aristo resulted in no clinically...
- Oral contraceptives In clinical studies in healthy subjects, steady-state dosing with Zonisamide Aristo did not affect serum concentrations of ethinylestradiol or norethisterone in a combined oral...
- Carbonic anhydrase inhibitors Zonisamide Aristo should be used with caution in adult patients treated concomitantly with carbonic anhydrase inhibitors such as topiramate and acetazolamide, as there...
- Zonisamide Aristo should not be used as co-medication in paediatric patients with other carbonic anhydrase inhibitors such as topiramate and acetazolamide (see section 4.4 Paediatric population).
- Caution is advised when starting or stopping zonisamide treatment or changing the zonisamide dose in patients who are also receiving medicinal products which are P-gp substrates (e.g.
Pregnancy
Important safety information For zonisamide MHRA/CHM advice: Antiepileptics: risk of suicidal thoughts and behaviour (August 2008) See Epilepsy . MHRA/CHM advice: Antiepileptic drugs: updated advice on switching between different manufacturers' products (November 2017) See Epilepsy and see also Prescribing and dispensing information . MHRA/CHM advice: Antiepileptic drugs in pregnancy: updated advice following comprehensive safety review (January 2021) See Epilepsy .
Breast feeding
Manufacturer advises avoid for 4 weeks after last dose.
Hepatic impairment
Avoid in severe impairment. Dose adjustments Initially increase dose at 2-week intervals if mild or moderate impairment.
Renal impairment
Dose adjustments Initially increase dose at 2-week intervals; discontinue if renal function deteriorates.
Medicinal forms
Solution,Capsule,Suspension
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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