David S. Bruyette, DVM, DACVIM (internal medicine)
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On Dec. 31, 2005, Eli Lilly discontinued four of its insulin products: Humulin L Lente insulin, Humulin U Ultralente insulin,
Regular Iletin II pork insulin, and NPH Iletin II pork insulin. Our challenges are to switch patients currently receiving
these products to comparable insulin preparations and to change our treatment approach in newly diagnosed diabetes mellitus
cases. Here are some suggested guidelines I use in my hospital.
Dogs
Newly diagnosed cases
1. Vetsulin (Intervet): This porcine-origin, zinc, lente insulin is intermediate-acting. Canine and porcine insulin have an identical amino acid
sequence, which eliminates the theoretical complication of the dog developing anti-insulin antibodies that may adversely affect
glycemic control. While the manufacturer 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. 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.
A Few Words About Blood Glucose Monitoring
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2. Humulin N (Eli Lilly): This is an intermediate-acting, human-origin insulin. Suggested starting doses are 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. The long-term
availability of this product is uncertain.
3. PZI insulin: This long-acting, protamine zinc, beef-pork-origin insulin has, in my experience, not been more effective in controlling
clinical signs in dogs than intermediate-acting insulins. This insulin 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. If you select PZI insulin, I recommend that you use PZI Vet (Idexx), as compounded insulins can provide inconsistent
treatment results. PZI is labeled for use in cats; for additional product information see the manufacturer's Web site:
http://www.idexx.com/.
4. Insulin glargine: To date, no information on the use of glargine in diabetic dogs is available (see the discussion below regarding insulin glargine and cats).
Changing insulin
In dogs receiving Humulin L Lente insulin, I recommend switching to either Vetsulin or Humulin N. The initial dose of Vetsulin
or Humulin N will remain the same as the dose used with Humulin L, but be sure to reassess the dog's clinical signs and perform
a serial blood glucose curve one week after changing insulin preparations.
Cats
Newly diagnosed cases
1. Insulin glargine (Lantus—Aventis): This is a modified, recombinant, long-acting insulin analogue approved for use in people. A study presented at the American
College of Veterinary Internal Medicine annual meeting in 2005 showed a high rate of remission (8/8 in remission within four
months, with 6/7 still in remission at one year) in feline diabetics with the use of glargine and a low-carbohydrate, high-protein
diet. The recommended starting dose is 0.5 U/kg given subcutaneously twice a day if the fasting blood glucose concentration
is greater than 360 mg/dl, or 0.25 U/kg given subcutaneously twice a day if the initial fasting blood glucose concentration
is less than 360 mg/dl.1-3
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