
Close-up of Iletin vial-1923. The insulin was all beef, came in varying strengths and was not highly purified.

Human activity profile for r-DNA/GE/GM R (Regular)/Neutral insulin. See links for cat & dog activity.
A short-acting, soluble, non-suspended insulin produced from r-DNA/GE/GM, bovine, or porcine sources. R or neutral insulin is basically zinc insulin crystals dissolved in clear fluid with nothing added to alter its action or speed[1]. From 1921 to the 1930's when PZI was developed, R was the only kind of insulin available.
While both R/neutral and semilente insulins are considered fast-acting, they differ in a few ways. As above, there's no suspension or buffer[2] in R/neutral; it's totally dissolved and soluble, meaning it can safely be used intravenously.
The very small insulin particles in semilente insulin are suspended by zinc[3]. Semilente is cloudy, has an acetate buffer and cannot be used intravenously.
R/Neutral insulin cannot be reliably mixed with Lente or Ultralente insulins[4][5]. Semilente can; the ratio of 3 parts semilente insulin to 7 parts ultralente insulin produces Lente insulin[6].
R/Neutral Insulins
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R/Neutral Insulins | |
---|---|
All Short acting | |
Hypurin Bovine Neutral | |
Hypurin Vet Neutral | |
Insuvet Neutral | |
Iletin I R (No longer produced.) | |
Hypurin Porcine Neutral Hypurin Pork Regular | |
Pork Actrapid | |
Iletin II R (No longer produced.) | |
Humulin R, Humulin S | |
Insuman Rapid | |
Actrapid, Novolin R ReliOn/Novolin R |
Further Reading
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References
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- ↑ US FDA-Humulin R
- ↑ Auburn University:Insulin Preparations-Regular Insulin
- ↑ Auburn University: Insulin Preparations-Lente
- ↑ Intermediate-Acting Insulin Preparations: NPH (Isophane) & Lente Diabetes Care-1980
Note--in 1980, there was only beef Lente-type insulin--no pork or r-DNA/GE/GMLente insulins - ↑ Resource Guide 2005-American Diabetes Association
- ↑ Auburn University: insulin Preparations-Lente Insulin