Canine Diabetes Wiki
Novolin N

Novolin NPH/isophane insulin.


NPH/isophane insulin information.

NPH Insulins, or "Neutral Protamine Hagedorn", now describes the set of insulins using Isophane / Protamine as their suspension. In North America, Humulin N and Novolin N are the most common brands of NPH insulin. Another term for this type of insulin is Isophane; it's commonly used to describe this insulin type outside of North America.

NPH was first launched in 1946 in Denmark by Novo Nordisk as the first longer-lasting neutral pH insulin for human use. "Hagedorn", was the name of the laboratory where it was invented. [1]

The difference between NPH/isophane insulin and PZI insulin is the amount of protamine in the suspension. PZI has more of it and this is what makes it a slow-acting insulin, in contrast to NPH/isophane being an intermediate-acting one for both dogs and people, [2] as the additional protamine extends the duration.

Specifications of NPH/isophane insulin[]


Iletin II NPH--pork isophane insulin--Canadian packaging.

British National Formulary [3] defines this type as: A sterile suspension bovine or porcine or of human insulin in the form of a complex obtained by the addition of protamine sulphate or another suitable protamine.

British Pharmacoepia and United States Pharmacopia definitions: [3]

Isophane Insulin

Sterile buffered suspension of insulin in the form of a complex obtained by addition of suitable protamine. Prepared from crystalline insulin. pH 6.9 - 7.5 iso-osmotic with blood. Contains for each 100 units of insulin, 300 - 600 g protamine sulphate and not more than 40 g zinc, a suitable bactericide and sodium phosphate as buffering agent.

USP specification: Sterile suspension of zinc insulin crystalline and protamine sulphate in buffered water for injection. Solid phase contain crystals of insulin protamine and zinc; 40, 80, 100 units/ml. Contains glycerol, metacresol, phenol sodium phosphate and zinc.

Additional details[]


Human time activity profile for r-DNA/GE/GM NPH/isophane insulin.

NPH is widely used for treatment of diabetic dogs. [4][5] With a peak of 1.5-6 hours and duration of 4-10 hours, if it is successfully used, twice-daily dosing is a must. [6]

This 1987 study [7] of direct comparisons between R and NPH insulins in dogs, found R insulin to be absorbed better than NPH and suggests that NPH insulin may have an earlier peak and shorter duration than previously thought.

Novo Nordisk's and Lilly's analog insulin mixes NovoLog and Humalog employ protamine/isophane suspension; non-mix Novolog and Humalog do not.

NPH/isophane insulins[]

The following commercial insulins are all generically NPH insulins:

Other commonly used names are:

  • NPH insulin, NPH
  • isophane insulin


  1. Gordon, Jana (April 2008). Insulin therapy: Past, present and future. DVM 360.
  2. Nelson, Richard (2006). Selecting an Insulin for Treatment of Diabetes Mellitus in Dogs & Cats-page 41. OSU Endocrinology Symposium.
  3. 3.0 3.1 British National Formulary-Isophane/NPH Insulin Definition. InChem. Cite error: Invalid <ref> tag; name "InChem" defined multiple times with different content
  4. Insulin Choice for Dogs. BD Diabetes.
  5. Ask the D Team-Some People Find it Inconsistent Also. Children With Diabetes (2000).
  6. Davidson, Gigi. Providing care for veterinary diabetics-page 3. International Journal of Pharmaceutical Compounding.
  7. Goeders LA, Esposito LA, Peterson ME. (1987). Absorption Kinetics of Regular (R)/(Neutral) & Isophane (NPH) Insulin in the Normal Dog. Domestic Animal Endocrinology.
  8. Hypurin Bovine Isophane Patient Information. Net
  9. Hypurin Bovine Isophane. Wockhardt UK.
  10. Prescribing Bovine Insulin.
  11. 11.0 11.1 Response to Withdrawal of Novo Porcine Insulins. CP/Wockhardt UK.
  12. Prescribing Porcine Insulin.
  13. Prescribing Novo Animal Insulin.
  14. Patient Information Leaflet-Pork Insulatard. Novo Nordisk.

More Information[]