Sulfisoxazole (gantrisin). Rationale: sulfisoxazole and other sulfonamides are chemically related to oral antidiabetic agents and may precipitate hypoglycemia. Mexiletine, an antiarrhythmic, is used to treat refractory ventricular arrhythmias; it doesn't cause hypoglycemia. Prednisone, a corticosteroid, is associated with hyperglycemia. Lithium may cause transient hyperglycemia, not hypoglycemia.