Side-by-side comparison of mechanisms, dosing, interactions, and stacking potential.
| Ostarine (MK-2866 / Enobosarm) | S-23 | |
|---|---|---|
| Category | SARMs | SARMs |
| Standard Dose | Research indicates 10-25 mg daily orally for 8-12 weeks. Phase 2 clinical trials used 1-3 mg/day with significant lean mass gains. | Research indicates 10-25 mg daily orally for 8-12 weeks. No human clinical trials — dosing extrapolated from rat pharmacology and anecdotal reports. |
| Timing | Once daily, morning or evening. Consistent timing. Half-life approximately 24 hours. No food timing requirements. | Split into 2 daily doses due to relatively short half-life (~12 hours). Morning and evening dosing. |
| Cycle Duration | 8-12 week cycles. PCT may be required depending on suppression level and cycle length. | 8 week cycles maximum recommended. PCT is absolutely mandatory due to profound HPG suppression. Allow full recovery before considering subsequent cycles. |
| Evidence Level | moderate_human | animal_plus_anecdotal |
Ostarine (enobosarm/GTx-024) is a nonsteroidal selective androgen receptor modulator that binds the androgen receptor with high affinity, inducing a conformational change that recruits coactivator proteins preferentially in muscle and bone tissue over prostate and seminal vesicles. This tissue selectivity arises from differential AR cofactor recruitment and 5-alpha reductase metabolism. Ostarine promotes lean body mass by activating AR-mediated transcription of anabolic genes (MYC, IGF-1) in myocytes while minimizing androgenic effects in reproductive tissues. It has demonstrated dose-dependent increases in lean mass in Phase 2 trials.
Research indicates 10-25 mg daily orally for 8-12 weeks. Phase 2 clinical trials used 1-3 mg/day with significant lean mass gains.
Once daily, morning or evening. Consistent timing. Half-life approximately 24 hours. No food timing requirements.
8-12 week cycles. PCT may be required depending on suppression level and cycle length.
S-23 is one of the most potent nonsteroidal SARMs developed, originally investigated by GTx, Inc. as a potential male hormonal contraceptive. It binds the androgen receptor with very high affinity, producing near-steroidal anabolic effects in muscle and bone while profoundly suppressing FSH and LH, leading to oligospermia and azoospermia in animal models. S-23 increases lean body mass and bone mineral density while reducing fat mass in a dose-dependent manner. The contraceptive effect was fully reversible in rat studies — spermatogenesis and fertility recovered completely after a 100-day washout period.
Research indicates 10-25 mg daily orally for 8-12 weeks. No human clinical trials — dosing extrapolated from rat pharmacology and anecdotal reports.
Split into 2 daily doses due to relatively short half-life (~12 hours). Morning and evening dosing.
8 week cycles maximum recommended. PCT is absolutely mandatory due to profound HPG suppression. Allow full recovery before considering subsequent cycles.
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