Andarine.

Quick Overview.

Andarine, commonly known as S4, is a first-generation Selective Androgen Receptor Modulator (SARM) developed by GTx Inc. It was originally investigated for the treatment of muscle wasting, osteoporosis, and benign prostatic hyperplasia (BPH). In the bodybuilding community, it is primarily used as a "cutting" or "hardening" agent, often compared to mild oral steroids like Winstrol or Anavar.[1]

While it is highly effective at preserving muscle mass and giving the physique a dry, vascular look, Andarine is infamous for a very specific and unique side effect: vision alteration. At higher doses, it binds to receptors in the eyes, causing a yellow tint to vision and difficulty adjusting to dark environments. Because of this, its popularity has waned in recent years in favor of newer SARMs like Ostarine or RAD-140.[2]

• Primary Use Case: Cutting, muscle hardening, and increasing vascularity.
• Mechanism: Selective agonism of the androgen receptor in muscle and bone, with partial agonism/antagonism in the prostate.[3]
• Who it is for: Advanced users looking for a pre-contest hardening effect who are willing to manage the vision side effects.
• Who it is NOT for: Beginners, anyone who drives at night for a living, or anyone easily panicked by temporary vision changes.

The Protocol & Usage Guide.

confidence_tier: well-established

Andarine has a very short half-life of approximately 4 to 6 hours. Because of this, it must be dosed multiple times per day to maintain stable blood levels.[4]

Standard Dosing Schedule

Cycle Length & Discontinuation Protocol

• Cycle Length: 6 to 8 weeks.
• The "5 On, 2 Off" Protocol: To mitigate the vision side effects, many users run Andarine for 5 days straight, followed by 2 days completely off the drug (usually the weekend) to allow the compound to clear the ocular receptors.
• Discontinuation (PCT): Andarine is moderately suppressive. A Post Cycle Therapy (PCT) using Enclomiphene (12.5mg daily for 4 weeks) or Nolvadex (20mg daily for 4 weeks) is required.[5]

Nutritional Support & Recommended Supplements.

confidence_tier: well-established

Safety, Interactions & Side Effect Management.

confidence_tier: well-established

Side Effect Profile

Contraindications

• Absolute: Individuals with pre-existing eye conditions (e.g., cataracts, glaucoma, macular degeneration).
• Absolute: Individuals who drive at night or operate heavy machinery in low-light conditions.
• Absolute: Teenagers whose endocrine systems are still developing.

Drug Interactions

• Alcohol: Severe. Combining oral SARMs with alcohol places immense stress on the liver.

Common Stacks & Combinations.

confidence_tier: community

Body Composition & Training Guide.

confidence_tier: community

• The Cosmetic Effect: Andarine is not a mass builder. Its primary value is cosmetic. It binds tightly to androgen receptors in adipose (fat) tissue, promoting fat oxidation and giving the muscles a very hard, dry, and vascular appearance.
• Strength Preservation: While in a deep caloric deficit, Andarine is highly effective at preserving strength, allowing users to lift heavy weights even when depleted.
• The Winstrol Comparison: In the bodybuilding community, Andarine is frequently compared to Winstrol (Stanozolol) because both compounds dry out the joints and harden the physique, though Andarine is significantly less liver-toxic.

Storage, Handling & Accessibility.

confidence_tier: well-established

• Storage: Store liquid solutions or capsules at room temperature in a cool, dark place.
• WADA Status: Banned in competitive sports under section S1.2 (Other Anabolic Agents).
• Cost & Accessibility: Widely available from research chemical vendors. Typically costs $50-$70 for a 30mL bottle (usually dosed at 50mg/mL).

Bloodwork Monitoring Guide.

confidence_tier: well-established

Comparison to Similar Compounds.

confidence_tier: well-established

Deep Dive (For Advanced Researchers).

confidence_tier: well-established

Mechanism of Action

Andarine (S4) is an aryl propionamide-derived non-steroidal selective androgen receptor modulator. It binds to the androgen receptor (AR) with a high affinity (Ki = 4 nM), which is roughly one-third the affinity of testosterone. In skeletal muscle, it acts as a full agonist, promoting protein synthesis.[6]

The Prostate Paradox

One of the most fascinating aspects of Andarine is its effect on the prostate. In preclinical rat models, S4 was shown to act as a partial agonist in the prostate. When given to intact male rats, S4 actually decreased prostate weight by competing with the much stronger endogenous dihydrotestosterone (DHT) for the androgen receptor. This led researchers to investigate S4 as a potential treatment for Benign Prostatic Hyperplasia (BPH).[7][8]

The Vision Side Effect Explained

The most notorious side effect of Andarine is the alteration of vision—specifically, a yellow tint to the visual field and delayed dark adaptation (difficulty seeing when moving from a bright room to a dark room).

• The Mechanism: The AR is expressed in various tissues, including the eyes. It is believed that Andarine binds to the ARs in the retina. Because Andarine's molecular structure is somewhat similar to certain anti-androgens (like bicalutamide), it may interfere with the visual cycle in the photoreceptors.[9]
• Reversibility: Clinical and anecdotal evidence universally agrees that this side effect is dose-dependent (rarely occurring below 50mg/day) and completely reversible. Once the drug is discontinued and clears the system (usually within 3-5 days), normal vision is fully restored.[10]

Clinical Trial Summary

While Andarine showed immense promise in preclinical models for muscle wasting and BPH, its clinical development was ultimately suspended by GTx Inc. in favor of Ostarine (MK-2866). Ostarine demonstrated a better safety profile, a longer half-life (allowing once-daily dosing), and lacked the ocular side effects that plagued S4. Consequently, Andarine never advanced past early Phase I trials.[11]

Frequently Asked Questions (FAQ).

confidence_tier: community

Q: Will the yellow vision be permanent? A: No. There are no recorded cases of permanent vision damage from Andarine. The yellow tint and night blindness disappear completely within a few days of stopping the drug.

Q: Why do people do the "5 days on, 2 days off" protocol? A: Because Andarine has a very short half-life (4-6 hours), taking 2 days off allows the drug to completely clear the ocular receptors, preventing the vision side effects from compounding and becoming unbearable.

Q: Can I just take it once a day? A: You can, but it is highly inefficient. Because of the 4-6 hour half-life, taking it once a day will result in massive spikes and crashes in blood serum levels. It should be split into at least two doses (AM and PM).

International Regulatory Status.

confidence_tier: well-established

Decision Tree.

confidence_tier: community

[Goal: Pre-Contest Muscle Hardening and Vascularity?]
  |
  +-- Do you drive at night or have eye conditions?
        |
        +-- (Yes) -> Do not use Andarine. Use Ostarine instead.
        |
        +-- (No) -> Are you willing to dose multiple times a day?
              |
              +-- (Yes) -> Take 25mg AM and 25mg PM.
                           If vision sides occur, switch to 5 days on, 2 days off.
                           Follow with 4 weeks of Enclomiphene (PCT).

Schema.org Data.

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  "@type": "MedicalEntity",
  "name": "Andarine",
  "alternateName": ["S4", "GTx-007"],
  "description": "A first-generation selective androgen receptor modulator (SARM) known for its muscle hardening effects and unique, reversible vision-altering side effects.",
  "legalStatus": {
    "@type": "DrugLegalStatus",
    "description": "Abandoned investigational drug. Not FDA approved. Banned by WADA."
  }
}

What we cited.