Oral hypoglycemic drugs
The use of oral hypoglycemic drugs to treat feline diabetes has been limited for a number of reasons. Many owners find administering tablets more difficult than injecting the cat with insulin. Drugs that stimulate insulin secretion (eg, sulphonylureas) require adequate β-cell function to be effective, and if there is an inadequate glucose-lowering effect, persistent hyperglycemia can lead to continued β-cell loss through glucose and lipid toxicity. These drugs may also stimulate accelerated islet amyloid deposition, exacerbating β-cell loss.
The α-glucosidase inhibitors (eg, acarbose) reduce intestinal glucose absorption [38] and are generally not effective in the treatment of feline diabetes alone but can be used in conjunction with insulin or other oral agents to gain better glycemic control. Cats given acarbose and fed a low-carbohydrate diet had a reduced insulin requirement and improved glycemic control, but similar results were achieved feeding the low-carbohydrate diet alone [39].
Chromium and vanadium are transitional metals that potentiate insulin action. Chromium has been shown to produce small but significant decreases in blood glucose in healthy cats [40], but there are no reports of its efficacy in diabetic cats. Vanadium is reported to reduce the insulin requirement of diabetic cats [41]. There is renewed interest in both metals in human medicine, but further investigation into their use in veterinary medicine is required before definite conclusions and recommendations are made.
Insulin-sensitizing drugs (thiazolidinediones and biguanides) increase the response of muscle, liver, and fat cells to insulin [42] and [43]. Their main effect is to decrease peripheral insulin resistance and, in muscle, to increase glucose uptake stimulated by insulin. They also reduce hepatic glucose production. In theory, these drugs should be invaluable in reversing insulin resistance, but there are currently no reports of their successful use in diabetic cats. Insulin sensitivity and lipid metabolism can be improved in obese cats using the insulin-sensitizing drug darglitazone [44].
