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 chief scientist who invented it.
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 (or in some cats, short-acting) one, as the additional protamine extends the duration.
Specifications of NPH/isophane insulin
British National Formularydefines 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:
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.
NPH is the most widely used type of insulin for treatment of diabetic dogs, but is shorter-acting and less predictable in cats. 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. See also Humulin N 101 for Cats at link below.
This 1987 study 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.
The following commercial insulins are all generically NPH insulins:
|Hypurin Bovine Isophane|
|Iletin I NPH|
(No longer produced.)
|Hypurin Porcine Isophane|
Hypurin Pork NPH
|Iletin II NPH|
(No longer produced.)
|Humulin N, Humulin I|
|Novolin N, Insulatard|
ReliOn/Novolin NPH, Protaphane
Other commonly used names are:
- NPH insulin, NPH
- isophane insulin
- Wiki cases--Feline NPH-isophane users
- Absorption Kinetics of Regular (Neutral), Isophane (NPH), and Protamine Zinc Insulin (PZI) in Normal Cats-Domestic Animal Endocrinology-1990
- Insulin Therapy in Cats With Diabetes Mellitus--JAVMA-1983
Contains peak, onset & duration information for NPH/isophane & PZI insulins in cats.
- Insulin Therapy in Cats with Diabetes Mellitus-JAVMA-1983
Some feline Time Activity information re: NPH/isophane & PZI insulins.
- Wiki cases--Canine NPH-isophane users
- Absorption Kinetics of Regular (Neutral) & Isophane (NPH)Insulin in the Normal Dog-Domestic Animal Endocrinology-1987
- The Use of Isophane (NPH) Insulin for the Control of Diabetes Mellitus in Dogs-Acta Vetinaria Scandinavia--1992
- InChem--with information on NPH/isophane insulins.
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- Selecting an Insulin for Treatment of Diabetes Mellitus in Dogs 7 Cats-Nelson-Page 41
- British National Formulary-Isophane/NPH Insulin Definition
- British Pharmacoepia (BP) & United States Pharmacoepia (USP)-Isophane/NPH Insulin Defined
- BD Diabetes-Insulin Choices for Cats
- BD Diabetes-Insulin Choice for Dogs
- Ask the D Team-2002- Some People Find it Inconsistent Also
- International Journal of Pharmaceutical Compounding-Page 3
- Humulin N 101 For Cats-Gorbzilla.com
- Absorption Kinetics of Regular (R)/(Neutral) & Isophane (NPH) Insulin in the Normal Dog-Domestic Animal Endocrinology-1987