You should not use Zonegran if you are allergic to zonisamide, or to other sulfa drugs such as sulfamethoxazole (Gantanol), sulfisoxazole (Gantrisin), or sulfamethoxazole-trimethoprim (Bactrim, Septra, Sulfatrim, SMX-TMP, and others). A sulfa drug allergic reaction can be fatal.
ZONEGRAN ® (zonisamide) is an antiseizure drug chemically classified as a sulfonamide and unrelated
to other antiseizure agents. The active ingredient is zonisamide, 1,2-benzisoxazole-3-
methanesulfonamide. The empirical formula is C 8 H 8 N 2 O 3 S with a molecular weight of 212.23.
Zonisamide is a white powder, pKa = 10.2, and is moderately soluble in water (0.80 mg/mL) and 0.1 N
HCl (0.50 mg/mL).