Nandrolone Phenylpropionate, also known as NPP is very similar to the very popular steroid Deca which is Nandrolone with a longer ester (Decanoate). Nandrolone Phenylpropionate is, therefore, a shorter acting Deca for all practical intents and purposes. Anecdotally, it seems to produce less water retention than its longer acting cousin, and this would be very consistent with injectable testosterones, where we find that shorter esters provide much less water retention.
It's a progestin, like any Nandrolone derivative, and is made by removing the carbon atom at the 19th position of the Steran Nucleus of testosterone. However, although it's a progestin, Nandrolone (regardless of ester) doesn't produce much of what we could properly call estrogenic side effects. Any side effects from Nandrolone Phenylpropionate would therefore more properly be termed progestenic in nature- as it only converts to estrogen at roughly 20% the rate of testosterone.
Regardless of ester, and water retention not withstanding, we find that all of the characteristics of found in one type of Nandrolone are found in any other. Nandrolone, probably owing to its progestenic nature has the ability to improve collagen synthesis as well as bone mineral content. Clearly this would be a huge benefit to athletes with connective tissue problems or other joint issues, although drug-tested athletes need to avoid Nandrolones because of their detectability in urine for a year to eighteen months after administration. Also, since it is progestin (with slight estrogenic ability), it probably has some very beneficial effects on the immune mediated anti-inflammatory process, thereby soothing joints as well as helping to heal them.
Nandrolone is one of the few steroids which has been used successfully in AIDS patients to stimulate weight gain, and although athletes using NPP in lieu of Deca find it to produce slightly less weight gain, this is probably a result of gaining less water weight. Nandrolone Phenylpropionate, is a more popular drug than Deca for use in cutting cycles recently, due to this fact.
This brings up the fact that although Deca has a very long active life, NPP has a much shorter one, and this means that people are forced to inject at least two times per week, with the more common protocol being every third day. Results are seen much more quickly with NPP as compared with Deca, and it's quickly becoming a much more popular alternative.
Both supply as well as demand for NPP is high, because many underground labs have recently been producing it in large quantities to keep up with the increased demand. Although an effective weekly dose will be relatively inexpensive, it will still cost more than Deca, owing to the injection frequency that it necessitates. On the Black market, $75-100 is the average price for a ten milliliter bottle, dosed at 100-200 mgs/ml.