This page describes pharmacological agents that may have legal restrictions, side effects, and drug interactions in your jurisdiction. Information is for educational research only — consult a clinician before considering any compound.

High-risk compound

Surface here is educational only; do not use without medical supervision. Our editorial verdict is SKIP-FOR-NOW — current cost / risk / redundancy puts it below the line.

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Ostarine

Extensively Studied

Non-steroidal SARM with bone/muscle tropism — milder than LGD-4033 in both efficacy and HPG suppression, but not innocent.

Aliases (7)

MK-2866 · Enobosarm · GTx-024 · S-22 · Ostabolic · MK 2866 · OSTARINE

TYPICAL DOSE

12.5-25 mg/day

Daily

ROUTE

Oral (capsule or liquid)

Oral

CYCLE

Modest receptor downregulation reported with ex…

Cycle length (8-12 wk)

STORAGE

Room temp; cool dry place

Room temp

Overview

What is Ostarine?

Ostarine (MK-2866, enobosarm) is a non-steroidal selective androgen receptor modulator (SARM) developed by GTx Inc., investigated for muscle wasting, cachexia, and osteoporosis. It is not FDA-approved and is banned by WADA for athletic use.

Key Benefits

Promotes lean muscle gain and bone density without the androgenic side effects (acne, hair loss, prostate effects) typical of anabolic steroids. Used in research for sarcopenia, muscle wasting in cancer cachexia, and stress urinary incontinence.

Mechanism of Action

Selective tissue-specific agonist at the androgen receptor (AR), with preferential anabolic activity in skeletal muscle and bone over prostate, sebaceous, and hair follicle tissue. Recruits coactivators that drive muscle protein synthesis without full prostatic activation.

Pharmacokinetics

PeakHalf-life

Approximate curve — visual aid only, not data-precise PK

▸ Cycle structure & PCT AAS oral

Cycle

8-12 week

Frequency

daily

PCT

Required

Phase 1 — On cycle

Ramp dose over week 1, hold steady through cycle weeks. Track baseline labs (TT/FT/E2/SHBG/HCT/lipids/LFTs) at week 0; recheck at week 4 and end-of-cycle.

Phase 2 — Bridge / cease

On the last dose, the ester clears over its half-life window . PCT begins after the active compound has cleared.

Phase 3 — PCT (post-cycle therapy)

Standard PCT is enclomiphene 12.5-25 mg/day or clomid 50/50/25/25 over 4 weeks (or nolvadex 20/20/10/10). HCG bridge optional during cycle to preserve testicular volume + faster restart. Bloodwork at PCT week 4 + 8 to confirm HPG axis recovery (LH, FSH, TT back to baseline).

Peptide Interactions

Creatine

Synergistic

independent additive lean-mass effect, no pharmacological collision. A-tier rationale.

Adequate protein (≥1.6 g/kg)

Synergistic

substrate for any anabolic stimulus. A-tier.

Vitamin D + zinc + magnesium (the user's V stack already)

Synergistic

supports endogenous T axis during PCT recovery.

LGD-4033, RAD-140, other SARMs:

Avoid

Compounds suppression, no proven additive efficacy. Common community mistake.

AAS (testosterone, trenbolone, anavar, etc.):

Avoid

Defeats the "milder than AAS" pitch; combines suppression and toxicity profiles.

17α-alkylated oral AAS (oxandrolone, methyltestosterone, stanozolol, oxymetholone):

Avoid

Liver-load stacking — ostarine's idiosyncratic hepatotoxicity plus 17α-alkyl liver strain is a known bad combination.

Hepatotoxic medications or supplements

Avoid

(acetaminophen ≥3g/day chronic, isoniazid, methotrexate, high-dose niacin, etc.).

Heavy alcohol:

Avoid

Liver-load compounding.

Other research-chem compounds with unknown contamination profiles

Avoid

multiplies counterfeit risk.

Quality Indicators

✓

Pharmacy-dispensed, intact packaging

Prescription tablets in original sealed packaging from a licensed pharmacy.

Generic vs branded

Generics are usually fine but bioavailability can vary slightly; track if you switch.

✗

Unbranded blister or counterfeit risk

Counterfeit pharmaceuticals are a known issue; verify pharmacy and lot if buying internationally.

What to Expect

Week 1-2
Nothing perceptible most days; occasional users report mild appetite increase, slightly improved gym recovery, joint comfort.
Week 3-6
Recovery between training sessions feels noticeably better; lean mass starts visibly accumulating; pump/fullness in muscles increases (likely glycogen + min…
Week 6-12
~3-6 lbs LBM, ~5-10% strength gains on compound lifts at moderate doses (15-25mg/day). Joint comfort often cited (likely real — ostarine is studied for oste…

Side Effects & Safety

Common (>10% users at typical 15-25 mg/day):
- HPG suppression — dose-dependent T drop (~25-40% at 3mg/day; higher at 25mg/day). LH/FSH suppression follows.
- Mild HDL reduction — ostarine reduces HDL cholesterol in essentially all users at 8+ weeks. Magnitude varies (~10-30% drop).
- Mild ALT/AST elevation — often subclinical, often resolves on cessation; concerning when persistent or symptomatic.
Less common (1-10%):
- Cholestatic hepatotoxicity — clinically apparent jaundice, dark urine, pruritus, marked LFT elevation. Multiple published case reports, mostly young men, mostly resolves on cessation but recovery can take 1-3 months and a minority require hospitalization.
- Suppression-related symptoms in PCT — fatigue, low libido, mood drop in the 4-8 week recovery window.
- Mild gyno — rare, related to T:E2 shift during recovery rather than direct estrogenic activity (ostarine doesn't aromatize).
- Visual disturbances — uncommon but reported; mechanism unclear (some SARMs interact with retinoid receptors at high doses).
- Headache, GI upset, mild nausea — minor, typical research-chem side-effect grab-bag.
Rare-serious (<1% but worth knowing):
- Severe cholestatic hepatitis with prolonged recovery — published cases; mechanism appears idiosyncratic (not predictable by dose alone). Some users with 5-10 mg/day developed clinical hepatitis; others on 50 mg/day did not.
- Drug-induced liver injury requiring transplant evaluation — at least one published case.
- Rhabdomyolysis (rare, training-context confounded).
- Cardiac concerns from chronic HDL suppression — theoretical, no MACE data exist for SARMs in any population.
- Counterfeit / contamination-related toxicity — ostarine sold as "ostarine" has been independently lab-tested (Cohen et al. 2017, JAMA, n=44 SARM products: 52% accurate label, 39% contained no SARM, 9% contained SARM not on the label, 25% contained substances banned by FDA) — so a "side effect" can be from an entirely different undisclosed compound.
- WADA AAF / banned-list positives — long detection window (multiple weeks); ostarine metabolites are detectable in urine for 6-9 weeks at very low concentrations.
Specific watch periods:
- Weeks 4-8: First likely window for LFT derangement to appear — many published case reports cluster here.
- End of cycle and into PCT (week 8-16): HPG axis recovery monitoring. T, LH, FSH, E2, hematocrit at 2 and 6 weeks post-cycle.
- Lipid panel at 6 weeks on, end of cycle, and 6 weeks post: HDL trajectory.