Metformin-Induced Type 1 Hypersensitivity in a Child with Antipsychotic-Induced Weight Gain

Address correspondence to: Constance Mennella, DO, Division of Child/Adolescent Psychiatry, Alpert Medical School of Brown University and Bradley Hospital, 1011 Veterans Memory Highway, East Providence, RI 02915, E-mail: [email protected]

To The Editor:

Metformin is a biguanide derivative oral antihyperglycemic. It is a first-line medication in the treatment of type 2 diabetes. More recently, it has been used to counteract weight gain associated with atypical antipsychotics in the pediatric population (Klein 2006; Arman et al. 2008). Type 1 hypersensitivity is an immediate allergy reaction in response to a specific allergen. Pathophysiology includes production of IgE antibodies, sensitized mast cells, and basophils. The subsequent release of histamine causes vasodilation. Here, we describe a case of a 10-year-old boy who developed a type 1 hypersensitivity reaction after his first dose of metformin 500 mg started to treat metabolic syndrome associated with successful use of risperidone as an antimanic agent.

Case Report

A 10-year-old boy was diagnosed 3 years previously with type I bipolar disorder after completing a Child Schedule of Affective Disorders and Schizophrenia Present and Lifetime version administered in the context of a research study by a physician board certified in pediatrics, adult psychiatry, and child/adolescent psychiatry. After diagnosis, risperidone was initiated as an antimanic agent. Family indicated significantly reduced bipolar symptoms, including reduced irritable and euphoric mood as well as aggression. However, shortly after initiation, family also noted side effects, including markedly increased appetite and request for nighttime...