Is Walmart insulin OK for pets?

Pet owner asks …

My dog is on Vetsulin 40/10, and Walmart sells insulin a lot cheaper, but they don't know which one to give me. They have three [kinds]: N, R and 70/30. Will one of them work in place of the Vetsulin?

David Bruyette, DVM, DACVIM, answers …

This is a very common question I've gotten from both pet owners and veterinarians, and to be honest, it's very confusing. So let's see if we can make this a bit clearer to everyone.

Vetsulin (Merck) is a veterinary-specific, FDA-approved intermediate-acting lente porcine-derived insulin that comes in a strength of 40 IU/ml and is sold in a 10-ml vial. The insulin must be administered with a U-40 insulin syringe or with an insulin pen designed for the product (Vetpen). Vetsulin is mixture of 35% amorphous and 65% crystalline insulin, which gives it two distinct onsets of action. The first, shortly after injection, helps to prevent rising glucose concentrations after a meal. The second controls blood glucose levels between meals.

Walmart sells an intermediate-acting NPH human-recombinant insulin that's not approved for use in animals (Novolin N; manufactured by Novo Nordisk and sold under the Walmart brand). It comes in a concentration of 100 IU/ml and is sold in a 10-ml vial. The insulin must be administered with a U-100 insulin syringe or with an insulin pen designed for the product. They also sell a human-recombinant insulin that comes in a strength of 100 IU/ml and is sold in a 10 ml-vial that is a mixture of 70% NPH insulin and 30% regular insulin (Novolin 70/30). The purpose of the 70/30 mix is similar to the rationale behind the Vetsulin mixture-providing control after a meal and between meals.

The question as to whether either of these NPH insulins can be used in place of Vetsulin requires more information. Does the pet owner want to switch because you're not seeing adequate control of the diabetes based on clinical signs and blood glucose measurements, or does the pet owner want to switch due to cost?

If you want to switch from Vetsulin to Walmart's brand of NPH because of price, that can be done, but there's no easy way to predict what the dose of NPH will be when starting the transition. Since the insulin preparations are very different in their potency and duration of action, the veterinary team will basically need to start over with an insulin treatment protocol. I suggest starting with 0.5 IU/kg twice a day, with an assessment of the patient's clinical progress and blood glucose curve in one week.

The pet owner, of course, will need to work very closely with your practice's veterinarian to ensure a successful and safe transition.

Dr. Bruyette is medical director at the VCA West Los Angeles Animal Hospital and Chief Medical Officer at Anivive Lifesciences.