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?

Explanation

## Why high-dose glibenclamide is right Neonatal diabetes caused by activating mutations in the K-ATP channel (KCNJ11/ABCC8) is a unique clinical scenario where the mutant channels remain open even when intracellular ATP is high, preventing the normal glucose-stimulated closure and subsequent insulin secretion. Sulfonylureas like glibenclamide bind directly to the SUR1 subunit of the K-ATP channel and force closure **independent of the ATP/ADP ratio**. This bypasses the genetic defect and restores insulin secretion, making high-dose sulfonylureas the diagnostic and therapeutic gold standard for this condition — not insulin therapy. This infant's seizures are due to severe hypoglycemia from absent insulin secretion; sulfonylurea-induced closure of the defective channels will allow insulin release and normalize blood glucose. ## Why each distractor is wrong - **Intravenous dextrose + diazoxide**: Diazoxide is a K-ATP channel opener used in hyperinsulinemic hypoglycemia (opposite pathology). Here, the channels are already pathologically open; opening them further would worsen hypoglycemia. Dextrose alone is only a temporary measure and does not address the underlying defect. - **Insulin infusion**: While insulin would acutely raise blood glucose, it does not address the genetic defect and bypasses the opportunity for diagnostic confirmation via sulfonylurea responsiveness. Insulin is not first-line for neonatal diabetes from K-ATP mutations. - **Glucagon + octreotide**: Glucagon raises blood glucose acutely but is not a definitive treatment. Octreotide suppresses insulin secretion, which would worsen the problem in a patient who already cannot secrete insulin. **High-Yield:** Activating K-ATP channel mutations → neonatal diabetes treated with **high-dose sulfonylureas** (not insulin); inactivating mutations → hyperinsulinemic hypoglycemia treated with diazoxide (K-ATP opener). [cite: Guyton & Hall 14e Ch 79; KD Tripathi 9e Ch 19; Neonatal Diabetes International Society guidelines]