Medical treatment for inoperable insulinoma: clinical usefulness of diphenylhydantoin and diltiazem.

This report describes a 78-year-old woman with insulinoma, treated with a combination of diphenylhydantoin and a calcium antagonist. The effectiveness of 200 mg of diphenylhydantoin and 180 mg of diltiazem was evaluated by measuring the levels of plasma glucose, immunoreactive insulin and immunoreactive insulin/plasma glucose after fasting or by the oral glucose tolerance test, and by the appearance of hypoglycemic symptoms. The mean concentration of fasting plasma glucose increased significantly during the treatment. The levels of immunoreactive insulin/plasma glucose and C-peptide immunoreactivity/plasma glucose significantly decreased. Symptomatically, no episode of hypoglycemia was noted during the combined treatment.