In people, diabetes is readily classified into Type I and Type II forms. The Type I human diabetic has no capacity for insulin secretion and is totally insulin dependent. The Type II diabetic develops diabetes later in life and simply has an inadequate (i.e. only partial) capacity for insulin secretion. Since insulin injections are unpopular among people, there is a demand for oral products to control blood sugar. Unfortunately, there is just no substitute for insulin; however, there are ways to make what little insulin there is work better and to potentially improve insulin secretion.
Insulin injections are not only unpopular with people receiving them; they are also unpopular with people administering them to their pets. Dogs are universally insulin dependent, like Type I human diabetics, and oral products have been a crashing failure in this species with the exception of acarbose (see below). In cats, there is a more positive outlook, though insulin is necessary for most patients. We will summarize what is available.
Oral Agents for Cats
It seems that in general, cats experience a diabetes that is analogous to human Type II diabetes mellitus; that is, these cats are still able to produce at least some insulin. Many feline patients (up to 30%) are able to experience diabetic regulation using oral medications alone; however, there is no way to identify these patients without trying medication and seeing if it works. For most of the oral products we are about to review, the goal is simply to improve the response to insulin injections.
Glipizide acts by increasing the pancreas’ secretion of insulin, and it is possible that a level of adequate control can be achieved by maximizing the pancreas’ secretion in this way. There is some capacity for side effects (15% of cats taking this medication will get an upset stomach) plus the majority of cats will not be controlled with this medication alone. Glipizide is often used as a last resort (i.e. when it is not possible to give insulin injections) as it increases the pancreas’ insulin secretion, it also increases the pancreas’ amyloid build up, which is what probably caused the diabetes in the first place.
At this time, glipizide is the only oral medication that can be expected to replace insulin injections and it only works for 25 to 30% of cats.
Other oral products reviewed below are meant as supplements to insulin injections.
A similar medication would be glyburide (there are many trade names). Glyburide was developed as a human alternative to glipizide and reportedly has fewer side effects potential in humans. There is vastly more veterinary experience with glipizide but if glipizide is not available, this might be a fair alternative.
Metformin (Diabex®, Glucophage®, Diaformin®)
This medication acts by increasing tissue sensitivity to insulin (i.e., it makes insulin stronger). Unlike glipizide and glyburide, metformin does not cause low blood sugar but lethargy, vomiting, and appetite loss have been reported side effects in cats. It cannot safely be used in cats with kidney insufficiency, with ketoacidosis or any other form of acidosis, or in cats where an iodine-containing radiographic contrast agent is going to be used in the next few days. Since ketoacidosis can come up unexpectedly in a diabetic pet, this product may not be a good choice. Feline studies are in progress but look promising for cats as a supplement to insulin treatment though drug interactions may be problematic. (Interactions have been noted with trimethoprim, ranitidine, cimetidine, furosemide, and digoxin.)
This is a trace mineral present virtually everywhere. It seems to have insulin-like properties and minimal side effects potential but is not likely to be helpful by itself. The form that has been studied was vanadium dipicolinate, which is not commercially available. The vitamin stores sell vanadium sulfate (Vanadyl Fuel®) but we do not know if it works as well as the dipicolinate form did in the research setting.
This product is a mineral supplement that can be found in many vitamin stores. It seems to potentiate the effects of insulin (i.e. the insulin becomes stronger). In cats, chromium picolinate would be used similarly to vanadium, i.e., as a supplement to insulin therapy.
Acarbose (Glucobay®, Precose®)
This medication inhibits the digestive enzymes responsible for breaking down starches. Its use leads to a more gradual absorption of sugars after a meal, which in turn leads to a more stable blood sugar level. The medication itself is not absorbed from the intestine and thus can be combined with other medications, but it can produce some intestinal side effects: flatulence, weight loss, and diarrhea. Acarbose was originally developed as a treatment for obesity since it interferes with sugar absorption and should not be used in underweight cats. Acarbose must be given with food if it is to work.
In cats, one of the most important aspects of the management of diabetes mellitus is the use of the low-carbohydrate diet and it would be incomplete not to mention it here. Most experts feel that this change alone is more significant in regulating the feline diabetic that any of the above supplements and medications combined. Diet in the management of a diabetic cat should not be taken lightly, so we encourage you to read more about it if you have not done so already.
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