The US Food and Drug Administration on Monday cautioned that epilepsy drug zonisamide (Zonegran) used to treat partial seizures in adults can cause excessive acidity of the blood in some patients.

 

Zonegran is sold by Woodcliff, N.J.-based Eisai Inc. However, zonisamide is sold by a number of generic drugmakers including Teva Pharmaceutical Industries Ltd., Mylan Inc, Novartis AG’s Sandoz unit and Watson Pharmaceuticals Inc, the FDA Web site reveals.

 

The announcement came after the agency reviewed data from two trials – one in adults and one in children. They found a persistent decrease in serum bicarbonate levels, a marker of metabolic acidosis, along with hyperchloremia, which both can cause breathing difficulties, irregular heart rhythms and fatigue. The findings show that pediatric patients may be more at risk of developing metabolic acidosis than adults.

 

Left untreated, metabolic acidosis can do long-term damage to the kidneys and bones and slow growth in children.

 

Federal health officials urge doctors to monitor patient’s blood serum levels during treatment with Zonegran even if they don’t show symptoms. If patients develop metabolic acidosis, doctors should consider reducing dosage or discontinuing use of the drug. Still, if patients continue the treatment, the FDA urges doctors to consider alkali treatment.

 

The FDA is also working with drug companies to add new warning information labels to the drug.

 

The FDA statement can be found here.