Assessment of Nifedipine Therapy in Hyperinsulinemic Hypoglycemia due to Mutations in the ABCC8 Gene.

CONTEXT: Previous case reports have documented the effectiveness of l-type calcium channel blockers (such as nifedipine and verapamil) for treating different forms of hyperinsulinemic hypoglycemia (HH).

OBJECTIVE

To systematically assess the glycemic response to nifedipine therapy in 11 patients with HH due to mutations in the ABCC8 gene.

DESIGN

Dose escalation of nifedipine therapy.

SETTINGS AND PATIENTS: Eleven children who were inpatients at a tertiary hospital and had diazoxide unresponsive HH due to mutations in the ABCC8 gene.

INTERVENTION(S): Nifedipine was administered orally at an escalating dose up to a maximum of 2.5 mg/kg/d.

MAIN OUTCOME MEASURES: Improvement in glycemic control, avoidance of hypoglycemic episodes, reduction of intravenous glucose infusion, and reduction in the requirements of other medical therapies.

RESULTS

The median age of the patients was 0.44 years (range 0.14 to 3.77). The ABCC8 gene mutations were homozygous in 3 cases, paternally inherited heterozygous in 4, and compound heterozygous in 4. 18F-DOPA PET/CT scan demonstrated a focal lesion in 2 cases and the rest were diffuse HH disease. One subject had nifedipine as monotherapy, whereas the rest had it in combination with octreotide/glucagon/diazoxide or cornstarch. After a median of 6.5 (3 to 23) days of maximal (2.5 mg/kg/d) dose of nifedipine therapy, none of the patients showed any improvement in glycemic control and patients continued to have hypoglycemic episodes.

CONCLUSIONS

HH due to mutations in the ABCC8 gene does not respond to nifedipine therapy. Mutations in the KATP channel genes might render the l-type calcium channel ineffective to therapy with nifedipine.