FDA MedWatch

Zonisamide (marketed as Zonegran, and generics) can cause metabolic acidosis in some patients

02/23/2009- FDA notified healthcare professionals that updated clinical data has determined that treatment with zonisamide, indicated as adjunctive therapy in the treatment of partial seizures in adults with epilepsy, can cause metabolic acidosis in some patients. Patients with predisposing conditions or therapies may be at greater risk for developing metabolic acidosis and 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 and is working with the makers of zonisamide to revise the product labeling to reflect this new safety information. The notification includes recommendations for healthcare providers, information for patients, and a data summary.

Read the MedWatch 2009 safety summary, including a link to the "Information for Healthcare Professionals" sheet, at

http://www.fda.gov/medwatch/safety/2009/safety09.htm#Zonisamide