Zonisamide Dosing for Idiopathic Intracranial Hypertension (IIH)
For patients with IIH, zonisamide should be initiated at 100 mg daily and titrated up to a goal dosage of 200-400 mg daily, with monitoring of electrolytes and renal function twice annually. 1
Dosing Protocol for Zonisamide in IIH
- Start with 100 mg daily as the initial dose 1
- Titrate up by 100 mg daily every 2 weeks until reaching the goal dose 1
- Target maintenance dose: 200-400 mg daily 1
- Monitor serum electrolytes and renal function twice annually 1
Mechanism of Action in IIH
- Zonisamide works through sodium and calcium channel blockade 1
- Modulates GABA receptors, which may help reduce intracranial pressure 1
- Functions as a carbonic anhydrase inhibitor similar to acetazolamide, reducing cerebrospinal fluid production 2
Clinical Considerations and Adverse Effects
- Zonisamide may be considered as an alternative when topiramate has excessive side effects 1
- Common adverse effects include irritability, confusion, and depression 1
- Zonisamide is associated with weight loss, which may be beneficial in IIH management as weight reduction is a primary treatment goal 1
- Increased risk of kidney stones - use caution in patients with history of nephrolithiasis 1
Comparison with Other Medications for IIH
- Acetazolamide is the first-line medication for IIH based on the IIHTT trial, which demonstrated improvement in visual field function at doses up to 4 g/day 3, 4
- Topiramate is another alternative that has carbonic anhydrase inhibitor activity and appetite suppression effects 1
- Zonisamide may be more lipophilic than acetazolamide, potentially leading to more effective control of increased intracranial pressure 2
Monitoring Recommendations
- Regular assessment of visual function and papilledema is essential 1
- Monitor for common side effects including mood changes and cognitive effects 1
- Check electrolytes and renal function twice yearly 1
- Assess headache frequency and severity, as headache management is a key component of IIH treatment 1
Important Precautions
- Women of childbearing age must be informed about potential teratogenic risks 1
- Patients should be counseled about possible cognitive side effects 1
- Zonisamide should be used with caution in patients with a history of kidney stones 1
- Weight monitoring is important as weight loss is a disease-modifying intervention in IIH 1