Exaggerated insulin secretory response in patients with insulinomas to midaglizole, a drug with alpha 2-adrenergic blocking activity.

Midaglizole is a new alpha 2-adrenergic blocking agent which increases insulin release from normal pancreatic islets. We studied its effect in four patients with insulinomas. In three patients oral administration of 150 mg of midaglizole caused a large increase in serum insulin and a corresponding decrease in plasma glucose. The magnitude of the response cannot exclude the possibility that midaglizole has direct beta cell stimulatory activity. Two of the three patients had operations, and their insulin responses to midaglizole became normal after removing the tumours. In contrast, midaglizole did not stimulate insulin secretion in the fourth patient. A midaglizole stimulation test might be useful in screening patients with insulinomas.