In 2005 Eli Lily announced the discontinuation of the majority of animal derived source insulins in addition to the lente
and ultralente lines of product. This changed the landscape of veterinary diabetic management. Ultimately, the best insulin
for your patient may be the one you are most familiar with; however, general guidelines will help choose the insulin that
will give you the best success with your patients. Selection of insulin type is not the sole decision in management of the
diabetic feline. Nutrition must be addressed and in some cases, the use of oral hypoglycemics may be considered in the cat,
but not the dog. Finally, providing your client and staff with proper monitoring choices is essential for successful management.
Insulin can be classified according to source as well as duration of action. Beef and pork were traditional species used for
insulin. Dogs, pigs, and humans have similar amino acid sequences of insulin, differing by only one amino acid between human
and dogs and pigs, which are identical. In contrast, the protein sequence of feline insulin is much more different than the
human sequence and differs by four amino acids but is quite similar to insulin derived from cows, differing by only one amino
acid. Clinically, the most significant aspect of these differences is the development of antibodies in the dog. The use of
beef source insulin is not recommended as in published studies the development of insulin antibodies in dogs administered
a beef/pork insulin combination ranged between 40 and 65%. Despite the source of insulin used, the few studies examining this
phenomenon do not suggest that insulin antibodies develop to a significant degree in the cat.
Currently, human recombinant is the most commonly available source of insulin, however, some specialized veterinary products
are available. Vetsulin (Caninsulin outside the US, Intervet/Schering-Plough Animal Health) is a porcine lente insulin that
is a mixture of 30% amorphous zinc insulin and 70% crystalline zinc insulin. In the past, a veterinary specific PZI (PZIVet)
consisting of a 90% beef and 10% pork mixture was marketed by IDEXX Pharmaceuticals but has since been discontinued, with
limited supplies remaining with distributors. Boehringer Ingelheim Vetmedica has recently announced a similar product based
on recombinant human sequences but published studies and details are yet to be available. Duration of insulin varies within
patients but can be somewhat reliably predicted. The chart below compares commonly available insulin potencies and a rough
guide to durations of action.
Two insulin types, lispro and aspart, are insulin analogues and are very short acting. However, no data regarding their use
in veterinary medicine is available at this time. Most recently, the use of Detemir in cats has been reported in a single
abstract presented at ACVIM in June 2009 (Roomp, 2009) with similar remission rates as glargine. No further data is available
at this time.