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Half-life (t½) is the time for plasma concentration to fall by 50% after peak. For esterified injectable androgens, the apparent t½ is controlled by two factors in series: the rate of ester hydrolysis at the depot/tissue interface, and the intrinsic metabolic clearance of the free steroid. The ester chain length dominates the first factor and thus the overall t½ for most injectable steroids. Understanding t½ values allows calculation of steady-state time (~5× t½), appropriate injection interval (typically 1–2× t½ for stable levels), and washout period (~5× t½ after last dose).
Testosterone Esters#
| Ester | t½ (approximate) | Injection frequency | Steady-state time |
|---|---|---|---|
| Testosterone suspension (no ester) | ~24h | Daily | ~5 days |
| Testosterone propionate | ~2–2.5 days | EOD | ~12 days |
| Testosterone phenylpropionate | ~4–5 days | 2–3× weekly | ~21 days |
| Testosterone isocaproate | ~7–9 days | 1–2× weekly | ~40 days |
| Testosterone enanthate | ~7–10 days | 1–2× weekly | ~45 days |
| Testosterone cypionate | ~8–10 days | 1–2× weekly | ~45 days |
| Testosterone decanoate | ~14–16 days | Weekly | ~70 days |
| Testosterone undecanoate (Nebido) | ~21 days | Every 3–4 months (clinical) | ~90 days |
| Sustanon 250 (blend) | Variable (peak ~8–10d; tail ~20d) | Weekly | Complex |
Nandrolone Esters#
| Ester | t½ (approximate) | Notes |
|---|---|---|
| Nandrolone phenylpropionate (NPP) | ~5–6 days | Short-acting; 2× weekly |
| Nandrolone decanoate (Deca) | ~14–16 days | Classic weekly dosing; long washout |
Other Injectable Esters#
| Compound | Ester | t½ (approximate) |
|---|---|---|
| Boldenone undecylenate | Undecylenate (11C) | ~14–21 days |
| Trenbolone acetate | Acetate (2C) | ~1.5–2 days |
| Trenbolone enanthate | Enanthate (7C) | ~7–10 days |
| Trenbolone hexahydrobenzylcarbonate | Hex/Parabolan | ~14 days |
| Drostanolone propionate | Propionate (3C) | ~2–2.5 days |
| Drostanolone enanthate | Enanthate (7C) | ~7–10 days |
| Methenolone enanthate | Enanthate (7C) | ~10–14 days |
| Stanozolol depot (aqueous) | None (suspension) | ~24–48h |
Oral Compounds (no ester; elimination t½)#
| Compound | Elimination t½ | Dosing frequency |
|---|---|---|
| Stanozolol oral | ~9h | BID |
| Oxandrolone | ~9–10h | BID |
| Methandrostenolone | ~3–6h | TID or split |
| Oxymetholone | ~8–10h | BID |
| Turinabol | ~16h | Daily or BID |
| Fluoxymesterone | ~9.2h | BID |
| Mesterolone | ~12h | BID-TID |
| Methenolone acetate (oral) | ~4–6h | BID-TID |
SARMs and Other Research Compounds#
| Compound | t½ (human) | Dosing |
|---|---|---|
| RAD-140 | ~60h | Once daily |
| LGD-4033 | ~24–36h | Once daily |
| MK-677 (ibutamoren) | ~24h | Once daily |
| Cardarine (GW501516) | ~16–24h | Once daily |
| Ostarine (MK-2866) | ~24h | Once daily |
Key Pharmacokinetic Calculations for Protocol Design#
Steady-state time: ~5 × t½ after starting dosing at a fixed interval
Washout time: ~5 × t½ after last dose (>97% cleared)
Loading dose option: to reach steady-state faster: 2× maintenance dose on day 1 → steady-state from day 1
Example: Testosterone enanthate, t½ = 9 days
- Steady-state: ~45 days (6.5 weeks) on weekly dosing
- Washout: ~45 days after last injection
- If study duration is 8 weeks, need to account for 6.5 weeks before stable levels are reached
Research Use Only. JuicedPharma does not provide medical advice.
Published by JuicedPharma Research Team · September 2026 · Category: Research Protocols & Science
