Treatment - General considerations
The mainstay of treatment for clinical DM in dogs and cats is insulin along with dietary modification. Goals include controlling BG below the renal threshold for as much of a 24 hr period as possible, which will improve clinical signs of DM, and avoiding clinically significant hypoglycemia.
Veterinarians use a variety of insulin products, but only two are presently approved by the FDA for use in dogs and cats. One of these is a porcine lente product (porcine insulin zinc suspension, Vetsulin) that is approved for both species. The other FDA-approved insulin, human recombinant protamine zinc insulin or PZI (Prozinc) insulin, is labeled as having an appropriate duration in cats, the only species for which it is approved. It is considered by clinicians as a long-acting insulin.
Because of limited controlled comparative studies, most expert recommendations are based on a combination of clinical and anecdotal experience. The guidelines Task Force strives to make evidence-based recommendations when data are available. However, the ability to make specific recommendations based on differences and preferences between veterinary insulin products is limited. Members of the Task Force most commonly use porcine lente insulin (Vetsulin) in dogs and glargine (Lantus) in cats, recognizing that other acceptable options used by many clinicians include Neutral Protamine Hagedorn (NPH; Humulin N, Novulin N) in dogs and PZI (Prozinc) in cats.
Although compounded insulin is available, its use is not recommended because of concerns about production methods, diluents, sterility, and insulin concentration consistency between lots. A study comparing commercially available insulin with its compounded counterparts showed that the manufactured insulin met all US Pharmacopeia requirements and only 1 of 12 compounders met US Pharmacopeia specifications at all time points. The variability between compounded insulins was also significant enough to have clinical consequences.11 It is also not recommended to dilute insulin because dilution can produce unpredictable results, alter insulin efficacy, and result in bacterial contamination.5,12