[Intake of disopyramide led to diagnosis of insulinoma]

A single dose of 250 mg disopyramide provoked severe hypoglycaemia and confusion in a 75-year-old woman. During subsequent investigation, fasting provoked symptomatic hypoglycaemia (venous blood glucose, 1.6 mumol/1) after 23 hours, plasma concentrations of insulin and C peptide then being 19 micrograms/ml and 0.85 pmol/l, respectively; computerised tomography and ultrasonography of the pancreas n.a.d. However, at laparotomy, a 10 mm diameter insulinoma was detected by intra-operative ultrasonography and palpation. The tumour was removed. To our knowledge, this is the first reported case of an insulinoma being detected due to intake of disopyramide.