The FDA issued an alert (February 23, 2009) about the risk of metabolic acidosis in patients treated with zonisamide (Zonegran). An excerpt from the alert on this anticonvulsant adverse effect:

Following a review of updated clinical data,  the FDA has determined that treatment with zonisamide can cause metabolic acidosis in some patients.  Zonisamide is indicated as adjunctive therapy in the treatment of partial seizures in adults with epilepsy.

The 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 patient’s antiepileptic treatment as appropriate.  If the decision is made to continue patients with metabolic acidosis on zonisamide, then alkali treatment should be considered. 

Other recent FDA alerts on anticonvulsants:

Antiepileptic drugs (AEDs): FDA requires warnings about suicidal thoughts and behaviors (suicidality)

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