FDA Drug Safety Communication

Following a review of updated clinical data, FDA has determined that treatment with zonisamide can cause metabolic acidosis in some patients. Patients with predisposing conditions or therapies, including renal disease, severe respiratory disorders, diarrhea, surgery, ketogenic diet, or certain other drugs may be at greater risk for developing metabolic acidosis following treatment with zonisamide. The risk of zonisamide-induced metabolic acidosis appears to be more frequent and severe in younger patients.

FDA recommends that healthcare professionals measure serum bicarbonate before starting treatment and periodically during treatment with zonisamide, even in the absence of symptoms. If metabolic acidosis develops and persists, consideration should be given to reducing the dose or discontinuing zonisamide (using dose tapering), and modifying the antiepileptic treatment as appropriate. If the decision is made to continue patients with metabolic acidosis on zonisamide, then alkali treatment should be considered.

This information reflects the current analysis of data available to FDA concerning this drug. FDA intends to update this communication when additional information or analyses become available.

View the full FDA Drug Safety Communication on FDA.gov