Deca - Durabolin ("Deca") is actually the brand name for Organon´s version of the compound Nandrolone Decanoate. This is a 19-Nor compound (some would say that it is the 19-nor compound)

Deca (and Nandrolone in general) doesn´t produce many estrogenic or androgenic side effects. This is because Deca has a very low rate of aromatization (conversion to estrogen via the aromatase enzyme), roughly equal to 20% the rate of Testosterone.

In one study of postmenapusal women, Deca impoved collagen synthesis (1), and in another study deca increased bone mineral content. (2)Both of these studies used VERY low doses, which were far too low to promote muscle growth. An athlete attempting to use Deca only for these two effects (increasing bone mineral content and collagen synthesis) should be using 100mgs of deca every week. That´s actually a higher dose than those two studies used successfully. Even at ½ of this dose, in HIV+ patients who have experienced significant wasting, a 100mg/E2W (every 2 weeks) injection of Deca resulted in a "significant increase in weight" (5). Deca is a very nice anabolic, causing slow gains in quality muscle. This could be due to its moderately strong binding to the Androgen Receptor, or its many positive non-Androgen-Receptor mediated effects. One such effect is nitrogen retention, which is a major factor in muscle growth and lean mass gains; in one study, with low-doses (65 mg/week) and high-doses of Deca (200 mg/week), both low-doses and high-doses resulted in significant nitrogen retention (33-52 g nitrogen/14 days, representing gains of 0.5 to 0.9 kg lean tissue/week), and body weight increased by 4.9 +/- 1.2 kg, including 3.1 +/- 0.5 kg lean body mass, and treadmill exercise performance (cardiovascular fitness) also improved (7).

Deca also has a very long active life. A 100mg shot Deca produced relatively active and stable plasma nandrolone levels until day almost 10, hence once a week shots are all that´s necessary for stable levels of nandrolond decanoate (as a side note, the nandrolone phenylpropionate used in this study was active, and only experienced a severe drop off around day 5, shooting NPP every 4th day is the way to go). Higher blood plasma levels of Nandrolone are found with Gluteal injections as opposed to Deltoid injections.

In another study of HIV+ men (6) we can see that deca ( 200mgs on week 1, 400 on week 2 and 600mgs for weeks 3-12) caused NO negative side effects in total or LDL cholesterol, triglycerides, or insulin sensitivity and there was a reduction of HDL cholesterol(8-10 points) in both groups. Also, in most studies with HIV+ subjects, deca also improved immune function.

Deca - Durabolin Side Effects

Many users have complained of water-retention with this drug Letrozole seems to be a preferred choice to combat this. This water retention would seem to make Deca more suitable for bulking rather than cutting, although it can be succesfully used for either.

Deca is a progestin (as are all nandrolones), unfortunately; it happens to stimulate the progesterone receptor 20% as well as progesterone itself (3), and this opens the door for many possible unwanted side effects (water retention, acne, etc...). This also may be the major reason that Deca is such a suppressive drug when it comes to your natural testosterone levels.

Always use Testosterone with your Deca - 200mgs, minimum, to avoid impotence and sexual dysfunction. For an anabolic effect from that Testosterone, double that, with an equal amount of deca (minimum). Also recommended is taking an anti-progesteronic drug with deca. Cabergoline and Bromocriptine are both good choices.

Deca - Durabolin Cycle

Deca can be used in a bulking cycle at up to 600mgs/week for an extended duration (12-16 weeks), or up to 400mgs/week in a cutting cycle (again, for 12-16 weeks), as long as something to combat water retention is present. Whichever purpose you decide to use Deca for, you still need to include Testosterone in your cycle and have some anti-progesteronic drugs on hand (see paragraph above).

Post Cycle Therapy (PCT), though beyond the scope of this profile, needs to be commented on. Due to the highly suppressive nature of Deca, I will speculate that testosterone in a deca-inclusive cycle needs to be run for at least 2 additional weeks upon cessation of Deca. We remember from the chart above that baseline testosterone levels took roughly a month to return. Hence, a nice long estered testosterone should be run about 2 weeks longer than deca, to prevent having a lag in time when the deca is not producing an anabolic effect, yet is still suppressing your natural testosterone levels. I´d also suggest that a particularly aggressive PCT be run after your cycle; nolvadex, HCG, and perhaps clomid should all be utilized in an effort to restore your natural hormone levels as quickly and efficiently as possible.

Deca Information
     (Nandrolone Base + Decanoate Ester)
     [19-nor-androst-4-en-3-one-17beta-ol]
     Molecular Weight(base):274.4022
     Molecular Weight (ester):172.2668
     Formula (base): C18 H26 O2
     Formula (ester):C10 H20 O2
     Melting Point (base): 122-124°C
     Melting Point (ester):31 - 32 C
     Manufacturer: Organon
     Release Date (in USA): 1962
     Effective Dose (Men): 200-600mgs/week (2mg/lb of Bodyweight)
     Effective Dose (Women): 50-100mgs/week
     Active life: 15 days
     Detection Time: Up to 18 months
     Anabolic/Androgenic ratio: 125:37

Source: steroid.com