Deca's half-life is about 7.5 days (Bagchus et al. 2005: terminal half-life 7–12 d).
Half-life estimate, not bloodwork or dosing advice. Disclaimer.
By Austin Witherow and Mason Calvert · Last updated · Sources
| Measure | 200 mg once a week, after the last dose |
|---|---|
| Highest amount | 269 mg, 2 days after the last dose |
| 50% of that left | 9.5 days after the last dose |
| 10% of that left | 27 days after the last dose |
| 3% of that left | 40 days after the last dose |
| Levels off | Around day 42 |
On the example input, 200 mg once a week, the curve levels off around day 42; after the last dose it takes 27 days to fall to 10% of its final 269 mg peak and 40 days to fall to 3%.
A single 200 mg injection fades on the same timeline from a lower peak of 128 mg of nandrolone, because every dose in the model decays at the same 7.5-day half-life.
This is the modeled amount of the drug itself. Drug tests look for metabolites and use different, often longer, windows. Pedplot does not estimate detection times.
| Frequency | Each dose | High point | Low point | Swing |
|---|---|---|---|---|
| Weekly (open in plotter) | 200 mg | 269 mg | 169 mg | 37% |
| Twice a week (open in plotter) | 100 mg | 231 mg | 201 mg | 13% |
| Every 3 days (open in plotter) | 85.7 mg | 226 mg | 206 mg | 9% |
Each schedule name opens that curve in the plotter.
The example input adds up to 200 mg a week. Given once a week as one 200 mg injection, the modeled amount swings 37% between its high and low point; split into 85.7 mg every 3 days, the swing is 9%.
The chart shows days 70 to 84 of a 12-week run, after all three schedules have levelled off.
The Deca-Durabolin SmPC gives three different half-lives: 6 days for release of the ester from the injection site into the blood, one hour or less for the ester to be split into nandrolone, and 4.3 hours for that splitting together with the distribution and elimination of nandrolone.
The 6-day release is the slow step, so it sets the shape of the curve after an injection. The 4.3-hour figure describes nandrolone after it has left the depot, which is why some pages give Deca's half-life in hours and others in days.
Wijnand et al. 1985 report the same 6-day release half-life in healthy volunteers and look like the study behind the SmPC figures.
Bagchus et al. 2005 measured a terminal half-life of 7 to 12 days, with the peak 30 hours after 50 or 100 mg and 72 hours after 150 mg. The plot uses 7.5 days, inside that range and 25% above the SmPC's release figure, with a 2-day time to peak.
The SmPC is for an Irish product that is now withdrawn, and only the Bagchus abstract could be read, so the data quality is medium.
| Compound | Half-life | Time to peak | Parent share | Levels off | To 10% after last dose |
|---|---|---|---|---|---|
| Deca | 7.5 days | 2 days | 64% | Day 42 | 27 days |
| NPP | 1.5 days | 1 day | 67% | Day 8 | 6 days |
| Test E | 4.5 days | 2 days | 72% | Day 24.5 | 17 days |
| EQ | 14 days | 4 days | 63% | Day 77 | 50.8 days |
Each row uses that compound's own example input. Of these, NPP falls to 10% of its final peak soonest after the last dose (6 days), and EQ takes longest (50.8 days).
The plot uses 7.5 days, the figure from Bagchus et al. 2005. The Deca-Durabolin SmPC gives 6 days for release from the injection site, and Bagchus et al. 2005 measured a terminal half-life of 7 to 12 days. At that rate the modeled amount falls to half its peak 9.5 days after the last injection, as the washout table shows.
In the model each injection climbs in a straight line to its peak 2 days later, the value in the key numbers table. Bagchus et al. 2005 found the peak depends on the dose: 30 hours after 50 or 100 mg, and 72 hours after 150 mg.
After the last injection in the example input (200 mg once a week), the modeled amount falls to 10% of its final 269 mg peak in 27 days and to 3% in 40 days (about 5.7 weeks), as the washout table shows. The slow step is release from the injection site, which the SmPC puts at 6 days; nandrolone itself is cleared within hours once it reaches the blood. This is drug remaining in the model, not a drug-test window.
They are different steps in the SmPC. The ester leaves the injection site with a half-life of 6 days, while 4.3 hours covers splitting the ester and clearing nandrolone once it is in the blood. The plot uses 7.5 days, and the notes on each source explain why the figures differ.
Data quality: Medium. How the model works.