Oral Antidiabetic Drugs for Cats

Diabetes mellitus (DM) is commonly diagnosed in cats. In humans, treatment regimens for non–insulin-dependent DM include various combinations of dietary modification, exercise, insulin administration, and one or more oral antidiabetic drugs, which have been extensively evaluated in humans but not in cats. Glucose toxicity is a phenomenon of chronic hyperglycemia and must be understood before interpreting response to any antidiabetic therapy. This article provides a critical review of the oral antidiabetic drugs glipizide, metformin, troglitazone, and acarbose. Diabetes mellitus (DM) is a common endocrine disorder in cats. It is estimated to affect 1 in 300 cats, with both forms of the disease defined by the ability of pancreatic beta cells to secrete insulin. Type I DM is characterized by the destruction of insulin-producing beta cells in the islets of Langerhans. Type I DM is always insulin dependent; therefore, the treatment of choice is insulin. Type II DM is characterized by defects in glucose-stimulated insulin secretion by the pancreas and in peripheral tissue sensitivity to and use of insulin. Initially, type II DM is non–insulin-dependent because of the ability of beta cells to produce some insulin. However, the progression of disease usually results in insulin dependence. In humans, treatment options for type II DM include various combinations of dietary modification, exercise, and administration of one or more oral antidiabetic drugs with or without insulin. The treatment options for type II DM in cats are not as diverse as those for humans for the following reasons: n It is difficult to discern in cats whether DM is insulin dependent, and most cats are treated as insulin-dependent diabetics. n Diabetic cats with finicky appetites may be difficult to manage with dietary changes. n Oral antidiabetic drugs have not been extensively evaluated in cats. (Nevertheless, understanding their possible role in treating feline diabetics is important for veterinarians. Use of these drugs in cats may become more commonplace, and clients often have questions regarding their use.) CE Vol. 23, No. 7 July 2001 633 n Glipizide is the only antidiabetic agent whose mechanism of action is directed at the endocrine