Just Ask the Expert: Your insulin options in diabetic dogs

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Q. With so many insulin products to choose from, how do I decide which insulin is the best for my canine patients?

A. Because there are several insulins to choose from, selecting an insulin for a newly diagnosed diabetic dog can be confusing. And how do you decide what to switch to in a dog that is responding poorly to a particular insulin? Here are my thoughts on where you might turn.

Dr. David S. Bruyette

Vetsulin (Merck Animal Health)

Vetsulin has recently been reintroduced to the veterinary market and is approved for use in both dogs and cats. This is the same product that was previously available from Intervet/Schering-Plough Animal Health.

This porcine-origin zinc Lente insulin is classified as an intermediate-acting insulin. Canine and porcine insulin have an identical amino acid sequence, which eliminates the theoretical complication of a dog's developing anti-insulin antibodies that may adversely affect glycemic control.

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One important change that occurred with the relaunch of Vetsulin is the manufacturer's recommendations regarding handling of the insulin. Vetsulin should be shaken thoroughly until a homogeneous, uniformly milky suspension is obtained. This is a markedly different way of handling insulin, so be sure to read the package insert for further handling instructions.

This insulin is available only at a concentration of 40 IU/ml, so make sure you provide U-40 insulin syringes to owners. Reassess the dog's clinical signs and perform a serial blood glucose curve one week after starting therapy.

While the manufacturer's package insert recommends once-a-day initial dosing, I have not found this to be effective in most of our patients. I suggest an initial starting dose of 0.5 U/kg given subcutaneously twice a day.

With the return of this product to the market, it will be my preferred insulin for the initial management of diabetes in dogs.

Humulin N

This intermediate-acting, human recombinant insulin is not approved for use in dogs, but it is safe and efficacious for controlling blood glucose concentrations in dogs.

The results of a recent study evaluating Humulin N's efficacy in 10 client-owned dogs showed that it effectively controls diabetes mellitus when given subcutaneously twice a day but that postprandial hyperglycemia can occur in some well-regulated dogs.1

The suggested starting dose is 0.5 U/kg given subcutaneously twice a day. Reassess the dog's clinical signs and perform a serial blood glucose curve one week after starting therapy.

ProZinc (Boehringer Ingelheim Vetmedica)

This long-acting, protamine zinc, human recombinant insulin is approved for use in cats. It has, in my experience, not been more effective in controlling clinical signs of diabetes in dogs than intermediate-acting insulins.

A recent study showed that it significantly decreased 10-hour mean blood glucose and serum fructosamine concentrations over a 60-day period in six dogs in which diabetes mellitus had been newly diagnosed as well as in 11 dogs previously treated with other forms of insulin.2

This product is available only at a concentration of 40 IU/ml, so make sure you provide U-40 insulin syringes to owners. I recommend an initial starting dose of 0.5 U/kg given subcutaneously twice a day.

Insulin glargine

Glargine (Lantus—Sanofi Diabetes), a modified, recombinant, long-acting insulin analogue, is approved for use in people. We generally consider using basal insulins such as glargine and detemir (see below) in dogs with diabetes mellitus that are not adequately controlled with Lente or NPH insulin.

Insulin glargine significantly lowered blood glucose concentrations in 12 client-owned dogs receiving the insulin twice a day in a recent study.3 This study concluded that insulin glargine is a potential and safe method of treatment in dogs with naturally occurring diabetes mellitus when administered subcutaneously twice daily. It also pointed out that in some studies, the use of other types of insulin in dogs appears to be more successful than using insulin glargine.

Insulin detemir

Insulin detemir (Levemir—Novo Nordisk) is a long-acting soluble insulin analogue capable of maintaining the basal level of insulin in people. In contrast to glargine, detemir is a newer synthetic insulin analogue with a long duration of action through modification of the insulin molecule. This modification facilitates reversible binding to plasma proteins, particularly albumin, from where it is released slowly into plasma. The modification also prolongs self-association in the injection depot, which prolongs absorption from subcutaneous tissue at the injection site and contributes to the long duration of action.

A recent study has shown that when administered to diabetic dogs, detemir has a greater effect and, thus, requires a lower dose than NPH and glargine insulins.4 But it also has a higher risk of inducing hypoglycemia.

I generally start at a dose of 0.1 U/kg given twice a day in dogs that have not been well-controlled with NPH or Lente insulins.

David S. Bruyette, DVM, DACVIM, VCA

West Los Angeles Animal Hospital

West Los Angeles, Calif.

Veterinary Diagnostic Investigation and Consultation

Malibu, Calif.

REFERENCES

1. Palm CA, Boston RC, Refsal KR, et al. An investigation of the action of Neutral Protamine Hagedorn human analogue insulin in dogs with naturally occurring diabetes mellitus. J Vet Intern Med 2009;23(1):50-55.

2. Maggiore AD, Nelson RW, Dennis J, et al. Efficacy of protamine zinc recombinant human insulin for controlling hyperglycemia in dogs with diabetes mellitus. J Vet Intern Med 2012;26(1):109-115.

3. Fracassi F, Boretti FS, Sieber-Ruckstuhl NS, et al. Use of insulin glargine in dogs with diabetes mellitus. Vet Rec 2012;170(2):52.

4. Sako T, Mori A, Lee P, et al. Time-action profiles of insulin detemir in normal and diabetic dogs. Res Vet Sci 2011;90(3):396-403.