4. Oral hypoglycemic agents are less likely than insulin to work in cats.
The only oral agent that has shown success in diabetic cats is glipizide. It is a sulfonylurea antidiabetic agent that works
by increasing insulin release. The long-term success rate is estimated to be approximately 35%7,8; which cats will respond cannot be predicted. The ideal patient for treatment with glipizide is a stable, nonketotic diabetic
cat of optimum to obese body weight that has mild clinical signs with no complicating diseases. Patients that are emaciated,
dehydrated, debilitated, have concomitant disease, or have recently lost > 10% of their body weight are not good candidates.
Glipizide can be tried in any cat whose owners refuse to give injections.
It can take up to 12 to 16 weeks to know if glipizide will work. If no response is seen after that time, administration should
be stopped and insulin therapy instituted. To me, this is the big problem with glipizide. It is not known exactly at what
point glucose toxicity becomes irreversible, but the sooner diabetic control is obtained, the better (see above). Empirically, taking 12 to 16 weeks trying glipizide is worrying.
Other oral hypoglycemic agents do not hold much promise for treatment of diabetes mellitus in cats, including metformin, vanadium,
chromium, and the glitazones. Acarbose can potentially be used in combination with insulin depending on the diet. If a high
protein diet is not possible in a diabetic cat, feeding a more standard diet and administering acarbose may achieve the same
goal.9 The dose is 12.5 to 25 mg/cat given twice daily with meals. Side effects are dose-dependent and include flatulence, semi-formed
stools, or diarrhea.
5. It's important to perform blood glucose curves.
Glucose curves are not perfect: They can be affected by deviation from normal routine and can vary from day to day.10,11 Therefore, glucose curves should always be interpreted in light of clinical signs. (Also related to this variation is the
important point that predicting the timing of a diabetic's nadir on the basis of previous serial glucose curve results and
obtaining a single sample at that time are unlikely to give a reliable result, i.e. spot-checking does not provide helpful information.10) Stress hyperglycemia can also falsely elevate results.
However, glucose curves serve two very useful purposes that other techniques do not. First, they can clearly show clinically
undetectable hypoglycemia. A glucose curve can document mild hypoglycemia that can be fixed before a seizure occurs. Thus,
periodic curves can be helpful even in a seemingly well-controlled patient. Second, and more importantly, other diagnostic
findings and clinical signs can suggest that control is lacking, but many reasons for poor control exist, including too low
and too high a dose of insulin. The only way to know how to change the therapy to gain control is by performing a glucose
6. The importance of home monitoring cannot be overemphasized!
One of the most crucial parts of judging the appropriateness of a dose, especially in cats, which are prone to stress hyperglycemia
as a species, is by monitoring clinical signs. If a diabetic is not polyuric, polydipsic, or polyphagic and its weight is stable or increasing, it is usually well-controlled.
Measuring urine glucose at home can aid in monitoring. Glucotest (Nestlé Purina) is my preferred option for monitoring urine
glucose at home in cats. First, urine glucose concentrations can be determined as needed to aid in assessing glycemic control,
especially when other data are conflicting. Consistently negative readings on urine glucose may indicate that insulin doses
are either adequate or excessive. Then a serial blood glucose curve will differentiate between adequate insulin therapy and
excessive doses that could result in hypoglycemia. Uniformly high urine glucose readings coupled with unresolved clinical
signs indicate that the insulin dose is inappropriately low.6 Second, urine glucose concentrations can be determined regularly (at least weekly) to help assess ongoing control. Changes
in urine glucose concentrations may alert the owner and clinician to loss of glycemic control and a need for reevaluation.
To avoid some of the problems associated with in-hospital blood glucose curves, performance of glucose curves at home has
taken on new importance. Home curves are likely the most accurate. For home glucose curves, it is not necessary for venous
blood to be collected. Capillary blood is suitable.12 Choices of sites are the ear, gum, footpads, or elbow callus (dogs). I do not recommend using the gum and footpads because
of the associated pain. It should also be recognized that glucose curves can vary from day to day when done at home as well.13 Two types of lancing devices are available. If using conventional automatic devices designed for pricking human fingertips,
choose a device with a variable needle depth. The appropriate depth for each patient can then be used.14 A needle can be used, especially if the marginal ear vein is the site of blood collection. Glucometers that require minimal
amounts of blood as well as those that sip the blood into the strip are desirable.
Training owners to perform home glucose curves takes time. Not all owners are suited to perform such a task. A small study
of nine owners of diabetic dogs (n=7) and cats (n=2) indicated that, at least in that population, the most frequently encountered
problems were the need for more than one puncture to obtain a blood drop, the creation of a sufficient blood drop, the need
for assistance in restraining the pet, and the resistance of the pet.15 Two dogs became more resistant over time, and the owners abandoned the technique. The two cats became more compliant, especially
because the technique was performed in a place chosen by the cat.15