All About Insulin
By Nyssa Reine-Salz, DVM, DACVIM
Insulin is a hormone produced by beta cells of the pancreatic islets of Langerhans and it helps regulate blood glucose. Diabetes Mellitus is the scientific term to describe partial or complete lack of insulin, which results in alteration of blood glucose.
Diabetes in dogs is typically similar to Type 1 diabetes seen in people. It results from an inability to produce insulin, most commonly related to immune-mediated destruction of the pancreas. Dogs with diabetes require lifelong insulin treatment.
Diabetes in cats more closely resembles Type 2 diabetes in people. A combination of insulin therapy, dietary management and lifestyle changes are utilized to manage diabetes in cats, and can even result in a remission of signs in cats, though often temporary. Most types of insulin used in cats have been associated with remission.
Several types of insulin are commercially available for diabetes maintenance. Just like with people, there isn’t an insulin product that is effective in managing every patient, and individual response to insulin therapy can be unpredictable.
The concentration of insulin in insulin products manufactured for people is 100 IU/ml, which is abbreviated as U100. The concentration of insulin in veterinary insulin products is 40 IU/ml, which is abbreviated as U40. There are specific syringes manufactured to be used with the specific concentration of insulin and it is imperative that these guidelines be followed to avoid errors of administration.
The advantage of the use of U40 insulin in dogs and cats is that because of the lower concentration, the physical unit is larger; making it easier to see the small doses they typically receive. Human insulins are also divided by their expected duration and onset of action. The common categories are rapid-acting, intermediate-acting and long-acting. These terms are applied to insulin used for dogs and cats, but the true response is varied from patient to patient.
Insulins FDA Approved for use in Dogs and Cats
Porcine Lente Insulin is categorized as an intermediate-acting insulin and is a U40 insulin. The product was first launched in the US under the brand name Vetsulin® in 2004. In Canada and other countries, this product is sold under the brand name Caninsulin®. It is a suspension of two different insulin products—an aqueous portion, which acts more quickly, and a crystalline portion for sustained activity. This unique property necessitates the labeling recommendation of vigorous mixing to assure the proper ratio of the two products.
The labeled starting dose for dogs is 0.50 U/kg a day; however, only approximately one third of canine patients can be regulated on single daily doses. Many endocrinologists recommend a starting dose of 0.25-0.5 IU/kg based on an increased likelihood of patient response. Most cats are managed well on Vetsulin® at 1-2 units/cat, twice a day. Vetsulin® is a veterinary prescription product sold through the veterinary channel and should only be administered with U40 syringes.
Insulin FDA Approved for Use in Cats Only
Protamine Zinc Insulin (PZI) is a long-acting insulin sold under the brand Prozinc® and is FDA approved for use in cats. PZI insulin is a 40 IU/ml insulin and is used at a starting dose of 0.2-0.07IU/kg SC every 12 hours for cats. Prozinc® is a veterinary prescription product sold through the veterinary channel and should only be administered with U40 syringes. Prozinc® is not typically recommended for the management of diabetes in dogs and its use is extra-label.
Human Insulins Extra-Label
Neutral Protamine Hagedorn (NPH) is an intermediate-acting insulin sold under the brands Novolin® N or Humulin® N. This insulin is a U100 insulin that is manufactured for human diabetes management but is used extra-label in dogs. The starting dose is 0.3 to 0.4 U/kg twice a day in dogs. The duration of action in cats is often insufficient, so its use is not typically recommend. NPH is available through most human pharmacies.
Insulin Detemir is a long-acting insulin sold under the brand Levemir®. It is a U100 insulin that is manufactured for human diabetes management. The starting dose of insulin Detemir in dogs is 0.1 Units/kg SC q12h. Canine insulin receptors appear to be four times more sensitive than human receptors to insulin Detemir, and therefore may be hard to dose in small dogs. Unlike less potent insulin product, it is recommended that blood glucose be measured within the first few days of therapy to assure hypoglycemia is not present. Detemir is available through most human pharmacies.
Insulin Glargine is a long-acting insulin sold under the brand Lantus®. It is a U100 insulin that is manufactured for human diabetes management but is often used extra-label in cats and less commonly in dogs. Starting dose for both dogs and cats is 0.25-0.5 IU/kg twice daily. Glargine is available through most human pharmacies.
The above dosage and drug content is strictly informational. All veterinary prescribed drugs and dosing should be followed closely for the pets under your facility’s care.
Nyssa Reine-Salz is a graduate of the University of Florida, College of Veterinary Medicine. She completed an internship in Small Animal Internal Medicine and Surgery and a residency in Small Animal Internal Medicine at the AMC in New York, New York. After achieving Board Certification in Internal Medicine, Dr. Reine-Salz was on staff at the Animal Medical Center with a focus on nephrology and endocrinology until 2009. Dr. Reine-Salz has worked for Merck Animal Health as an Internal Medicine Consultant with an emphasis on diabetic support since 2012.