Adelphi NPP 100mg (Nandrolone Phenylpropionate)

Adelphi Research NPP (Nandrolone Phenylpropionate) 100mg/ml is the fast-acting version of Deca-Durabolin, delivering the same quality mass gains, joint support, and collagen synthesis benefits but with a shorter ester that allows quicker onset, faster clearance, and easier PCT timing. Nandrolone is one of the most studied anabolic steroids in clinical medicine, with research confirming lean mass increases of 3-6 kg over 12-16 week cycles alongside significant improvements in connective tissue health.

NPP vs Deca-Durabolin: Why Choose the Short Ester?

Nandrolone is available in two ester forms. The compound itself is identical; only the release speed differs:

• NPP (Phenylpropionate, this product): half-life 2.5-4 days. Inject every other day or 3x per week. Effects noticeable within 1-2 weeks. Clears system in 5-7 days. PCT can begin 5-7 days after last injection
• Deca-Durabolin (Decanoate): half-life 15 days. Inject 1-2x per week. Effects take 4-6 weeks to appear. Takes 21+ days to clear. PCT delayed by 3 weeks after last injection

NPP is preferred by users who want faster feedback from the compound (confirming they tolerate Nandrolone before committing to a long ester), faster resolution of side effects if they occur, and a more straightforward transition to PCT without the extended 3-week waiting period that Deca requires.

How Nandrolone Builds Muscle

Nandrolone has an anabolic rating of 125 and an androgenic rating of just 37, making it 25% more anabolic than testosterone with only a third of the androgenic activity. This ratio produces quality, sustainable muscle gains with significantly fewer androgenic side effects (less acne, less hair loss, less aggression) compared to testosterone at equivalent anabolic doses.

Nandrolone also increases collagen synthesis by up to 250% according to research in the Journal of Clinical Endocrinology and Metabolism. This dramatically improves joint health, tendon resilience, and connective tissue repair. Users running heavy compound movements (squats, deadlifts, bench press) frequently report that joint pain diminishes or disappears during Nandrolone cycles, allowing higher training intensity and volume.

Suggested Protocol

• Dose: 300-400mg per week (100mg every other day or 150mg 3x per week)
• Cycle length: 10-14 weeks
• Always run with a testosterone base: Test E at 300-500mg/week or Test Prop at 300mg/week. Running Nandrolone without testosterone causes “Deca dick” (erectile dysfunction from prolactin/progesterone dominance)
• Prolactin control: Cabergoline 0.25mg twice per week. Nandrolone is a 19-nor that raises prolactin
• AI if needed: Arimidex 0.25mg EOD (primarily for the testosterone base; NPP aromatises only slightly)
• PCT start: 5-7 days after last NPP injection (vs 21 days for Deca)
• PCT: Nolvadex 40/40/20/20mg for 4 weeks

What to Expect

• Week 1-2: initial effects noticeable. Subtle fullness, improved recovery between sessions
• Week 3-6: steady mass accumulation. Joint comfort improves noticeably. Strength climbing
• Week 7-14: peak gains. Quality, dense muscle with moderate water retention (less bloat than high-dose Test)
• Total lean gain: 3-6 kg over a full cycle with proper training and nutrition

Side Effects

• Prolactin elevation: can cause erectile dysfunction, low libido, and lactation if unmanaged. Cabergoline is essential
• Moderate testosterone suppression: full HPTA shutdown. PCT mandatory
• Water retention: mild-moderate (significantly less than Dianabol or high-dose Testosterone)
• Hair loss: low risk. Androgenic rating of 37 makes Nandrolone one of the safest compounds for hair
• Liver toxicity: none (injectable)
• Cardiovascular: moderate impact on cholesterol. Less severe than oral steroids

Key Facts

• Active ingredient: Nandrolone Phenylpropionate 100mg/ml
• Manufacturer: Adelphi Research
• Anabolic / Androgenic: 125 / 37
• Half-life: 2.5-4 days
• Aromatisation: low (approximately 20% the rate of testosterone)
• Progestogenic activity: yes (raises prolactin, requires Cabergoline)
• Detection time: 12+ months

For a broader comparison of injectable compounds, read our Injectable vs Oral Guide. For PCT timing specific to Nandrolone, see our PCT Guide. Browse all injectable steroids.