Nandrolone Phenylpropionate (NPP) is a testosterone derived anabolic androgenic steroid. NPP is a 19-nor steroid due to a modification of one atom. Compared with dihydrotestosterone, NPP has less androgenic activity while having more anabolic activity than unmodified testosterone.

This substance is very similar to the more common and well-known Deca Durabolin with main ingredient nandrolone decanoate. The main difference between the two is the ester attached to the nandrolone compound. Deca 100 Fast has a shorter phenylpropionate attached than the more popular long acting decanoate.

Nandrolone releases from the site of injection over a 2 to 3 weeks period. NPP 100 Fast releases from the injection site and lasts about a week in the system. NPP 100 Fast acting is therefore best when being injected every 2 to 3 days to keep the levels in the system level. Apart from the time these two substances releases and last in the system, Deca Durabolin and NPP 100 Fast are virtually interchangeable. Nandrolone phenylpropionate shows a sharp increase in blood serum levels of the free form of nandrolone within 24 to 48 hours from the time of injection. Because of this sharp increase and quick release of nandrolone this product is sometimes preferred to the longer acting version. After athletes compete and they battle with joint pain they prefer this substance because the longer acting version will take too long to kick in.

This substance is not as androgenic as testosterones, but this does not mean it is not androgenic at all. At high doses it will have some androgenic effects. In other words, at low doses, you will have very few androgenic effects but at high doses you might experience oily skin, acne, and body/facial hair growth. Male pattern hair loss, deepening of voice and clitoral enlargement in females is also possible. Liver toxicity with this substance is very unlikely because it is not a c-17 alpha alkylated.