A 6-month-old male infant from rural Maharashtra presents with severe hypoglycemia (blood glucose 28 mg/dL) and seizures. Genetic testing reveals a heterozygous activating mutation in KCNJ11 (K-ATP channel gene). The structure marked **B** in the diagram is defective — the mutant channels remain constitutively open despite elevated intracellular ATP. Which of the following is the most appropriate initial pharmacological management?