Nandrolone phenylpropionate (NPP; US name nandrolone phenpropionate) is an injectable anabolic steroid. It is nandrolone (19-nortestosterone) with a short phenylpropionate ester attached. Organon sold it as Durabolin, and the FDA approved it in 1959. It is the faster-acting relative of nandrolone decanoate (Deca-Durabolin): both release the same hormone, but NPP leaves the injection site about three times faster.
No NPP product is approved in the US today. At Organon’s request, FDA withdrew the Durabolin approval in 2018 because the product was no longer marketed, and every US generic listing is discontinued. The controlled human evidence is thin: one pharmacokinetic study in healthy men and a handful of small, mostly old clinical trials.
This page summarizes what FDA records, the pharmacokinetic study, the clinical trials and regulators report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | Anabolic-androgenic steroid; ester of nandrolone (19-nortestosterone) |
| Brand / approval | Durabolin (Organon), NDA 011891, approved October 30, 1959; generics under several ANDAs |
| Route | Intramuscular injection in oil |
| Former US strengths | 25 mg/mL and 50 mg/mL |
| Doses in cited human studies | Single injections of 50 mg or 100 mg, where a dose is reported |
| Half-life | Release from the injection site ≈ 2.4 days (vs ≈ 7 days for the decanoate in the same study); free nandrolone is cleared within hours |
| Nandrolone content | ≈ 67% of the ester’s weight (100 mg ester ≈ 67 mg nandrolone) |
| US status | No approved product; Durabolin NDA withdrawn September 7, 2018; Schedule III controlled substance |
| WADA status | Prohibited at all times (S1.1, anabolic androgenic steroids) |
What it is
Nandrolone is testosterone without the methyl group at carbon 19, which is why it is also called 19-nortestosterone (Kicman, Br J Pharmacol 2008). The phenylpropionate ester has the formula C₂₇H₃₄O₃ and a molecular weight of 406.6 g/mol (PubChem). Nandrolone itself weighs 274.4 g/mol, so about 67% of each milligram of ester is nandrolone.
The ester has no hormonal activity of its own. It makes the molecule more fat-soluble, so it stays in the oil depot for a while after injection. Once it leaves the depot, the ester is cut off and free nandrolone is released (Minto et al., JPET 1997). The ester only sets the release rate:
| Ester | Side chain | Molecular weight | Nandrolone share |
|---|---|---|---|
| Phenylpropionate (NPP, Durabolin) | 9 carbons, including an aromatic (benzene) ring | 406.6 g/mol | ≈ 67% |
| Decanoate (Deca-Durabolin) | 10-carbon straight chain | 428.6 g/mol | ≈ 64% |
How nandrolone differs from testosterone
In tissues that contain the enzyme 5α-reductase, such as the prostate and skin, testosterone is converted to the stronger androgen dihydrotestosterone (DHT). Nandrolone is converted to 5α-dihydro-19-nortestosterone instead, which binds the androgen receptor less strongly than nandrolone itself. This is the accepted explanation for nandrolone’s greater muscle-to-androgenic ratio compared with testosterone in animal assays. Kicman also notes that nandrolone has some progestational activity (Kicman 2008).
“NPP is a milder Deca.” Online sources often describe NPP as a gentler or “cleaner” form of nandrolone, and quote exact anabolic:androgenic ratios. NPP and the decanoate release the same hormone, so the ester changes only timing, not the kind of effects. In the only head-to-head human study, a single 100 mg dose of either ester pushed testosterone down to the same low point. We could not trace the commonly quoted ratios to an original source, so we do not repeat them.
Pharmacokinetics
The only published human pharmacokinetic study of NPP compared it with nandrolone decanoate in healthy young men. Each man received a single 100 mg injection in 4 mL of arachis (peanut) oil into the gluteal muscle: NPP in 7 men and the decanoate in 6 (Minto et al., JPET 1997). The authors noted that no earlier study had reported NPP pharmacokinetics. The study was funded by Organon.
| Measure (mean) | NPP 100 mg | Decanoate 100 mg |
|---|---|---|
| Time to peak nandrolone | 1.0 day | 5.0 days |
| Peak nandrolone | 30.9 nM (≈ 8.5 ng/mL) | 13.5 nM (≈ 3.7 ng/mL) |
| Absorption half-time from the depot | 2.4 days | 7.0 days |
| Mean residence time | 4.5 days | 10.1 days |
| Days with nandrolone at or above 5 nM | 5.1 days | 9.4 days |
| Total exposure (AUC) | 155 nmol·day/L | 144 nmol·day/L |
Three points follow from these numbers:
- Faster in, faster out. NPP gave a peak more than twice as high, reached about four days sooner, and fell away sooner. Total exposure over the study was similar.
- The depot sets the duration. Once released, free nandrolone was cleared with a half-time of about 0.25 days (≈ 6 h). How long a dose lasts depends almost entirely on release from the injection site.
- Only part of the dose reached the blood. Absolute bioavailability, measured against an intravenous dose, was 53–56% for NPP and for the decanoate given the same way.
Approved medical use and regulatory history
FDA approved Durabolin (NDA 011891) on October 30, 1959, as a new molecular entity (Drugs@FDA). Drugs@FDA lists 25 mg/mL and 50 mg/mL injections from Organon and generic makers, all discontinued. FDA’s site does not hold a copy of the label, and we could not locate an official US prescribing information document, so we do not list labeled doses here.
The US National Cancer Institute’s SEER drug database lists NPP as used for metastatic breast cancer and severe growth retardation in children, and as an add-on in chronic wasting diseases (NCI SEER*Rx).
How it left the US market:
- July 21, 1999. At the request of Steris Laboratories, FDA withdrew Steris’s generic nandrolone phenpropionate 25 mg/mL and 50 mg/mL approvals because they were no longer marketed (64 FR 33098).
- September 7, 2018. FDA withdrew approval of Durabolin (NDA 011891, 25 and 50 mg/mL). The holder, Organon USA, had told FDA the product was no longer marketed and asked for the withdrawal (83 FR 39103).
Neither notice cited a safety finding. They were routine withdrawals of products no longer being sold.
What the research shows
Controlled human trials of NPP are few, small and mostly decades old. None tested it for muscle or strength in healthy people. The larger body of nandrolone trials, in dialysis, HIV wasting and osteoporosis, used the decanoate; see the nandrolone decanoate page.
Breast cancer
NPP was used as hormonal therapy for metastatic breast cancer in women. In a South African trial run from 1968 to 1972, perimenopausal women were assigned to drostanolone propionate (Masteril) or NPP (Bennett et al., S Afr Med J 1975). Response rates were similar: 34.5% with drostanolone and 39% with NPP. The abstract does not report group sizes or survival.
Anemia from bone marrow failure
A randomized, double-blind trial compared NPP with placebo in anemia from bone marrow failure (Branda et al., Arch Intern Med 1977). Of the 21 evaluable patients, 7 had aplastic anemia, 6 myelofibrosis and 8 refractory anemia:
- 6 patients improved: 3 on NPP and 3 on placebo.
- One patient with myelofibrosis improved dramatically on placebo alone, with hemoglobin rising from 5.4 to 15.8 g/dL.
- The authors concluded that no substantial improvement could be credited to nandrolone. They warned that uncontrolled reports can mistake spontaneous remissions for drug effects.
Surgery
Two randomized trials gave a single NPP injection around surgery:
| Trial | Participants | Regimen | Main result |
|---|---|---|---|
| Zawilska et al. 1990 | 183 patients over 40 having major abdominal surgery | Nebulized heparin alone, nebulized heparin plus NPP 50 mg, or standard heparin injections | Deep vein thrombosis in 16%, 7.9% and 7.8%; clinically important bleeding in 1.7%, 1.6% and 7.8% |
| Pourmand et al., Aging Male 2008 | 54 men, mean age 70, having open prostatectomy | NPP 100 mg before surgery vs sesame-oil placebo | Symptom score at 24 h 6.18 vs 9.77 (p under 0.001); at 48 h 4.48 vs 5.55 (p = 0.06) |
The thrombosis abstract does not report a statistical test for adding NPP to nebulized heparin. The prostatectomy study was a pilot, and its authors called for larger trials.
Knee pain
A 2004 Cochrane review of drugs for patellofemoral pain (pain around the kneecap) found one trial of 43 participants. Intramuscular NPP improved pain and function compared with placebo injections. The reviewers concluded that nandrolone “may be effective, but is too controversial” for this use, given its risks (Heintjes et al., Cochrane 2004).
Side effects and risks
No NPP-specific safety data from large trials exist. The risks below come from the human pharmacokinetic study and from what is known about anabolic steroids as a class.
Hormonal suppression and fertility
Even one dose shuts down the body’s own testosterone production. After a single 100 mg NPP injection, the men’s testosterone fell from a mean of 17.6 nM (≈ 508 ng/dL) to a low of 2.3 nM (≈ 66 ng/dL) at about day 5 (Minto et al. 1997). The authors noted that the low point corresponded to the 1–3 nM seen in castrated men. Testosterone stayed below 10 nM for a mean of 5.8 days, compared with 11.0 days after the decanoate, and was back to baseline by day 13. NPP suppresses as deeply as the decanoate. Suppression from a single dose is shorter only because the hormone is released over a shorter time.
The class effects that follow from this suppression include testicular atrophy and impaired sperm production. Kicman’s review notes that recovery of fertility can take from months up to about a year after stopping (Kicman 2008).
Virilization in women and children
Nandrolone’s weaker androgenic profile does not prevent masculinizing effects. Kicman’s review states that nandrolone will cause hirsutism (male-pattern hair growth) and eventually virilization in women and children. The review describes virilization in women as irreversible, and hirsutism as at best only partly reversible after stopping.
Class risks of anabolic steroids
Kicman’s review lists these risks for anabolic steroids as a class:
- higher LDL and lower HDL cholesterol, which add to the risk of heart attack and stroke;
- liver toxicity, linked mainly to the oral 17α-alkylated steroids; NPP is an injected ester and is not 17α-alkylated;
- peliosis hepatis (blood-filled cysts in the liver) and an increased risk of liver tumors;
- gynecomastia (breast growth in men).
The size of each risk depends on sex, dose and duration of use.
Legal status and use outside medicine
In the US, nandrolone is named in the federal definition of an anabolic steroid, which also covers its esters (21 U.S.C. 802(41)). Anabolic steroids and their salts, esters and ethers are Schedule III controlled substances (21 CFR 1308.13). With no approved product, any NPP sold in the US comes from outside the regulated drug supply.
In sport, nandrolone (19-nortestosterone) is named in S1.1 of the 2026 WADA Prohibited List and is prohibited at all times, in and out of competition (2026 Prohibited List, Tractatenblad 2026, 25).
For the testosterone ester with the same side chain, see testosterone phenylpropionate.
Key takeaways
- Same hormone as Deca, faster release. NPP and nandrolone decanoate both deliver nandrolone. NPP’s absorption half-time from the injection site was about 2.4 days, against 7.0 days for the decanoate.
- Higher, earlier peak. A single 100 mg dose peaked at about 1 day, at more than twice the decanoate’s peak, with similar total exposure.
- Strong suppression even from one dose. Testosterone fell to castrate-range levels within about 5 days and recovered by day 13.
- Thin clinical evidence. The controlled human data are a handful of small trials in breast cancer, marrow-failure anemia, surgery and knee pain. The marrow-failure trial found no benefit over placebo.
- No longer approved in the US. Durabolin’s approval was withdrawn in 2018 at the holder’s request, and NPP remains Schedule III and banned in sport.
Sources
- Organon USA Inc. Durabolin (nandrolone phenpropionate) injection, NDA 011891. Drugs@FDA.
- Food and Drug Administration. Merck Sharp & Dohme Corporation, et al.; withdrawal of approval of four new drug applications. Federal Register. August 8, 2018;83:39103 (FR Doc 2018-16982). govinfo.
- Food and Drug Administration. Steris Laboratories, Inc.; withdrawal of approval of 55 abbreviated new drug applications. Federal Register. June 21, 1999;64:33098–33100 (FR Doc 99-15660). govinfo.
- National Cancer Institute. SEER*Rx: Nandrolone phenpropionate. NCI SEER*Rx.
- National Center for Biotechnology Information. Nandrolone phenpropionate, PubChem CID 229455. PubChem.
- Kicman AT. Pharmacology of anabolic steroids. Br J Pharmacol. 2008;154(3):502–521. PubMed.
- Minto CF, Howe C, Wishart S, Conway AJ, Handelsman DJ. Pharmacokinetics and pharmacodynamics of nandrolone esters in oil vehicle: effects of ester, injection site and injection volume. J Pharmacol Exp Ther. 1997;281(1):93–102. PubMed.
- Bennett MB, Helman P, Palmer P. Hormonal therapy of breast cancer with special reference to Masteril therapy. S Afr Med J. 1975;49(49):2036–2040. PubMed.
- Branda RF, Amsden TW, Jacob HS. Randomized study of nandrolone therapy for anemias due to bone marrow failure. Arch Intern Med. 1977;137(1):65–69. PubMed.
- Zawilska K, Tokarz A, Misiak A, et al. Nebulized heparin and anabolic steroid in the prevention of postoperative deep vein thrombosis following elective abdominal surgery. Folia Haematol Int Mag Klin Morphol Blutforsch. 1990;117(5):699–707. PubMed.
- Pourmand G, Salem S, Karami A, Baradaran N, Mehrsai A. Anabolic-androgenic steroid effects on early morbid symptoms after open prostatectomy: a pilot study. Aging Male. 2008;11(3):123–127. PubMed.
- Heintjes E, Berger MY, Bierma-Zeinstra SM, Bernsen RM, Verhaar JA, Koes BW. Pharmacotherapy for patellofemoral pain syndrome. Cochrane Database Syst Rev. 2004;(3):CD003470. PubMed.
- 21 U.S.C. § 802(41), definition of anabolic steroid; 21 CFR § 1308.13(f), Schedule III anabolic steroids. LII; eCFR.
- World Anti-Doping Agency. The 2026 Prohibited List (effective January 1, 2026), as published in the Netherlands Treaty Series. Tractatenblad. 2026;25. Officiële bekendmakingen.