By Wendy C. Brooks, DVM, DipABVP
Educational Director, VeterinaryPartner.com
Brand Name: Glucotrol
Available in 5 and 10 mg tablets
Diabetes mellitus is an enormous problem in human medicine. There are hundreds of thousands of human diabetics who require treatment and there are research labs all over the world seeking ways to make life easier for diabetics. This research spills over into veterinary medicine and can be helpful to our animal patients.
Human diabetic patients are classified as Type I (completely unable to produce any insulin) and Type II (unable to produce enough insulin). Type I patients do not respond to oral treatments to reduce blood sugar; they require insulin injections whereas Type II patients may respond to oral medications provided their pancreas has some remaining insulin-producing capacity. While it is not difficult to classify human patients, this is not so straightforward for animals. Diabetic dogs, for example, are completely insulin dependent, analogous to Type I, and have no response to treatments other than insulin injections. Some cats, but not most, appear to fit into a feline version of the Type II category, meaning some diabetic cats (perhaps as many as 30%) can actually make do with oral medications.
These oral medications work by causing the pancreas to release insulin more effectively (obviously if there is no insulin to release, this does not help). They also help increase tissue sensitivity so that smaller doses of insulin may have a greater effect. Some cats will respond adequately to this treatment and not need insulin injections at home. There is no way to predict whether an individual cat will be one of these without trying the medication and seeing what happens.
How this Medication is Used
Photo by Laura Hedden.
Glipizide is an oral medication (pill) commonly scripted out to a human pharmacy. It is given twice a day. Since it will not be known if a cat will respond, monitoring for the first month or so is very important. Weekly blood sugar levels are recommended as will help your veterinarian determine the dose of glipizide. Some cats will be partial responders, which may or may not be adequate to control their diabetes. Some cats will respond at first but ultimately require insulin later on.
During treatment with glipizide, it is important for a cat to eat a low-carbohydrate diet. This kind of dietary management is also helpful in treating diabetes mellitus and will help maximize the medication's effect.
Glipizide is not effective for diabetic dogs.
If one is late on giving this medication, it can be given anyway as long as there are at least a couple of hours between doses. If a dose is skipped altogether, do not double up on the next dose.
- Hypoglycemia (blood sugar dropping too low) will occur in some cats on this medication. This is one of the reasons why monitoring is so important. Hypoglycemia is reported to occur in approximately 15% of cats on glipizide.
- Nausea and appetite loss occurs in approximately 15% of cats on glipizide. Giving the medication with food is helpful. Appetite loss is a dangerous situation for a diabetic.
- Liver enzymes will increase on diagnostic testing with the use of this medication. This does not appear to be a harmful problem but you should be aware of this reaction if you note such elevated enzymes on a routine screening test. If the cat's liver enzyme elevations are accompanied by actual signs of illness, the medication should be discontinued. If the ALT enzyme becomes greater than 500 IU/L then the medication should be discontinued. Liver reactions of significance occur in approximately 8% of cats on glipizide.
Let your veterinarian know at once if your diabetic cat becomes uninterested in food. The cat will not simply eat when it is hungry enough.
Interactions with other Drugs
The following drugs may reduce the effect of glipizide: corticosteroids (dexamethasone, prednisone), thyroid hormone supplements, phenothiazine antihistamines, diuretics.
Monoamine oxidase inhibitors such as selegiline, or beta blocker heart medicines (such as atenolol), and antifungals may enhance the activity of glipizide as can the antacid cimetidine (Tagamet®).
Concerns and Cautions
Pre-existing liver or kidney disease will predispose the patient to hypoglycemic reactions.
If ketones are discovered in the patient’s urine, this is an indication that oral hypoglycemic treatments will not be useful. Only insulin can stop ketonuria.
One of the most important cautions with this medication is that by increasing the release of insulin, glipizide also increases the secretion of other proteins in the pancreas. It is generally abnormal protein deposition in the pancreas that caused the diabetes mellitus in the first place, thus the use of glipizide may lead to progression of pancreatic destruction. For this reason, we recommend glipizide as a last resort when insulin administration cannot be given or for a select few cats who are sensitive to insulin injections.
Because the diabetic dog is completely insulin dependent, oral medications are not a meaningful option. In diabetic dogs, insulin by injection is the only realistic treatment. Glipizide is an option for some diabetic cats; most cats will require insulin for regulation.
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