What's the Best Insulin for Treating Dogs with Diabetes Mellitus?

I am writing you regarding my 11-year old male Weimaraner, Duke. He has always been in good health but over this past week he has had 2 ”accidents” where he has urinated in the bed. He has also been drinking a lot more water than usual and urinating more too.

I  took him to the vet because I had a feeling he might be diabetic. My veterinarian confirmed that it was indeed diabetes mellitus and started him on 10 units of NPH, once after breakfast and once after dinner.  He has improved since starting the insulin, but remains quite thirsty and continues to urinate excessively.

Now I know that this will not give very good control alone because NPH is only a long-acting insulin. I am a Type 1 diabetic, diagnosed when I was 12 years old, so I have quite a bit of experience dealing with this disease. I want my poor puppy to be as controlled as possible so he does not feel like I do when my sugars are out of control— lethargic, nausea, headaches, unquenchable thirst, urinating all the time, and just plain crappy! Not to mention the stress this puts on the on the rest of the body.

If dogs are anything like people, I believe that Duke needs an insulin mixture that will bring his blood glucose down to normal and keep it leveled out. I have been giving him the rapid-acting insulin analog Humalog (insulin lispro) along with the NPH and that seems to be working really well, with marked improvement in his thirst and urination.  The only problem is that he needs 4-6 injections of Humalog each day. I was hoping you have had experience with something that would give him the same control as Humalog but with less injections daily.

In the past, I have used short-acting Regular insulin (before Humalog was invented) but I do not remember how the dosing went. I do have much better control with the Humalog but I am also on an insulin pump, so NPH insulin is no longer necessary.

Any help you can give to allow my dog Duke better control long term without so many injections would be greatly appreciated.

My Response:

In dogs, veterinarians commonly start with an intermediate-acting insulin (NPH or Vetsulin) twice a day (1,2). In some dogs, I find it necessary to add a short-acting insulin to the longer-acting insulin preparation, but many dogs can achieve adequate glucose control without giving more than 2 injections per day.

Insulin of choice for canine diabetics
In my opinion, the insulin of choice for most dogs is Vetsulin (porcine insulin zinc suspension; Merck Animal Health) (3). The main advantage of Vetsulin (known as Caninsulin outside the USA (4), is that it is actually composed of both short- and long-acting insulin components (see Figure below, showing the duel peaks of activity) (5,6). So giving Vetsulin is like administrating NPH together with a second, short-acting insulin preparation, like you are doing now.  However, Vetsulin works better than NPH for most dogs because it has a longer duration of action than NPH.

Timing of meals and insulin injection
The short-acting amorphous fraction of the Vetsulin, which composes 35% of the insulin activity, acts like regular insulin or Humulog, mainly to control the rise in blood glucose after each meal (6).  To help prevent severe rises in glucose after meals, however, it is also important to give the insulin before meals, instead of after the food is ingested, as you are doing now. This protocol will allow the short-acting insulin to be absorbed into the blood stream and ready to act to lower the blood sugar as soon as the food is absorbed from the gastrointestinal tract (7).

The only time I don't do this insulin-feeding protocol is in dogs that don't always eat their meal well; but even in those dogs, I never wait long after the meal is finished to give the insulin. Instead, I always give the insulin injection as soon as possible, once the dog has eaten a sufficient amount of food.

Vetsulin (porcine insulin zinc suspension), with it's 2 peaks of insulin activity

References:

1. Nelson RW. Canine diabetes mellitus In: Ettinger SJ, Feldman EC, eds. Textbook of Veterinary Internal Medicine: Diseases of the Dog and Cat. Seventh Edition ed. St. Louis: Saunders Elsevier, 2010;1449-1474.
2. Davison LJ. Canine diabetes mellitus In: Mooney CT, Peterson ME, eds. BSAVA Manual of Canine and Feline Endocrinology. Fourth ed. Quedgeley, Gloucester: British Small Animal Veterinary Association, 2012;116-132.
3. Vetsulin website. www.vetsulin.com 
4. Caninsulin website. www.caninsulin.com
5. Monroe WE, Laxton D, Fallin EA, et al. Efficacy and safety of a purified porcine insulin zinc suspension for managing diabetes mellitus in dogs. J Vet Intern Med 2005;19:675-682.
6. Fleeman LM, Rand JS, Morton JM. Pharmacokinetics and pharmacodynamics of porcine insulin zinc suspension in eight diabetic dogs. Vet Rec 2009;164:232-237.
7. Cobry E, McFann K, Messer L, et al. Timing of meal insulin boluses to achieve optimal postprandial glycemic control in patients with type 1 diabetes. Diabetes Technol Ther 2010;12:173-177.