Neutral Protamine Hagedorn (NPH) insulin, also known as isophane insulin, is an intermediate-acting insulin given to help control blood sugar levels in people with diabetes. The words refer to neutral pH (pH = 7), protamine a protein, and Hans Christian Hagedorn, the insulin researcher who invented this formulation. It is designed to improve the delivery of insulin, and is one of the earliest examples of engineered drug delivery.[1]
It is used by injection under the skin once to twice a day. Onset of effects is typically in 90 minutes and they last for 24 hours.[1] Versions are available that come premixed with a short-acting insulin, such as regular insulin.[2]
The common side effect is low blood sugar.[1] Other side effects may include pain or skin changes at the sites of injection, low blood potassium, and allergic reactions.[1]