Now that Walmart is offering an NPH insulin (RelinOn) for approximately $25.00 a vial, I am getting questions from some people wanting to switch their pets to save money. Unfortunately, not all insulin is the same which means switching may not save money. Let me explain:
There are many types of insulin used in human and veterinary medicine. Insulin is classified based on its duration of action into short, intermediate and long-acting. In veterinary medicine, short-acting insulin is used primarily to bring down blood sugar levels quickly in patients with diabetic ketoacidosis. Short-acting insulin is called regular and usually has an R after the trade name. It only lasts a few hours and requires careful monitoring while the animal is hospitalized. NPH (isophane) insulins have an intermediate length of action that is often used twice a day to control blood sugar levels. Intermediate-acting insulin has an N after the trade name. Glargine and PZI insulin are long-acting insulin which in some patients, may be dosed once a day.
Most diabetic dogs are controlled with twice daily injections of either NPH or Vetsulin insulin. Vetsulin made by Intervet is a combination of amorphous and crystalline zinc insulin derived from pigs. NPH is a human product that is used off label in dogs. Since dogs are genetically closer to pigs than humans, it is believed there is less chance of dogs developing antibodies with Vetsulin versus NPH. In my experience, dogs who are on NPH insulin most often are on the brand Humulin N produced by Eli Lilly. ReliOn N is also NPH insulin but produced by Novo Nordisk. For Walmart’s distribution the company renamed its product Novolin N as ReliOn N.
Unfortunately, the two different brands of NPH insulin are not interchangeable.
According to veterinary endocrinologist, Dr. Mark Peterson, each firm uses different manufacturing techniques and ingredients to create their product. That means the two types of insulin do not react the same when injected into the patient. Therefore, a patient who changes from one brand to another must be re-regulated to find the proper dose of the new insulin. In my experience, the cost of doing blood glucose curves, urinalysis and/or fructosamine level far outweigh any potential savings. Also, use the proper syringe to match the concentration of the insulin.
WARNING! Before changing the type, brand, dose or frequency of insulin for your pet, please check with your veterinarian. NPH of any brand is not used in cats.
-Peterson, Mark. Humulin Versus Novolin NPH Insulin: Are They Bioeqivalent?, Insight into Veterinary Medicine (Blog), April 3, 2014.