Oral medication

Because caregivers are often reluctant to begin insulin injections on their pets, vets will often offer an oral-medication alternative such as Glucotrol, Glipizide, Metaformin, or Acarbose. These oral medications either reduce insulin resistance or stimulate the pancreas to produce more insulin (assuming it still can).

Use in cats

Unfortunately for cats, diabetes is a condition with many vicious circles, and these medications, in the ~80% of feline cases where they don't work, tend to make diabetes worse instead. Worse, vet literature often says that 6 to 8 weeks of oral med treatment should be tried before giving up, and it's quite possible for an untreated diabetic (or one on an ineffective treatment) to die of starvation, dehydration, or ketoacidosis within that time. The odds of oral medication leading to a successful regulation of your cat are poor, and the odds of things getting much worse during the treatment are more likely.

Recent studies in cats(including those below) are now pointing toward a deterioration cycle of

(Type II diabetes -> (hyperglycemia <-> amyloidosis) -> Insulin dependence)

in cats. Since Glucotrol/Glipizide are shown to promote amyloidosis in the presence of hyperglycemia (hardly an unusual condition in a diabetic), there is every reason to believe that these meds can only make things worse. (Though Dr. Galloway disagrees. )

Possible reasons why veterinarians keep trying this course on cats:

• Most caregivers are (or the vets believe they will be) unwilling or unable to give regular insulin shots
• Diabetic cases that are well-treated are rare enough for many vets that they don't have a chance to track successful versus unsuccessful treatments
• Nobody is financially motivated to show negative results of a drug therapy.

Use in dogs

In dogs, results of oral insulin boosters are even worse, and so oral medications are not used to attempt to regulate dogs, only as an adjunct to insulin therapy. The most commonly used adjunct in dogs is Acarbose (Glucobay, Precose), which slows down digestion of starches and therefore moderates post-prandial glucose levels. There are unpleasant side effects so it's only used in difficult canine cases. Chromium Picolinate is sometimes also tried, because it seems to boost the use of insulin in normal dogs, though it seems to fail in this task with diabetic dogs.

The reason oral diabetes medications are not successful in dogs is because all of them are designed to stimulate the beta cells of the pancreas into producing more insulin. Most dogs have insulin-dependent diabetes, which means their beta cells are not capable of producing insulin--with or without medication stimulations. Basically, there's nothing in the endocrine pancreas able to be stimulated.

Further Reading

• How Glipizide and similar medications cause amyloidosis and permanently damage the cat pancreas
• Islet Amyloid -- A culprit in Type-II diabetes
• Dissenting opinion (Glipizide is ok) from Dr. Pru Galloway
• Deterioration cycles in diabetic cats
• Effect of Glipizide for Feline Diabetes Mellitus-JAVMA 1993
• JAVMA 1997-Intensive 50 Week Evaluation of Glipizide in 50 Previously Untreated Diabetic Cats

• More about Acarbose as an addition to insulin for dogs.

• Controlling Diabetes Mellitus Without Insulin.
  • Article covers Glipizide, Glucotrol, Metaformin and Acarbose use in cats; use of Acarbose as an adjunct to insulin in dogs.
• Oral diabetes medications in cats and dogs