# Andarine (S4)

*Also known as: S4, Andarine*

SARM with notable vision-related side effects; short half-life requiring divided dosing.

## Overview

Andarine (S4) is a non-steroidal selective androgen receptor modulator, one of the earliest studied in the class, developed for muscle-wasting and osteoporosis indications. It binds the androgen receptor with tissue-selective anabolic activity in muscle and bone while aiming to limit androgenic effects on the prostate. The compound has a short roughly 4-hour half-life, requiring divided twice-daily oral dosing, and its pharmacokinetic profile relies on canine data, so the human model is approximate. It is best known for a distinctive vision-related side effect, including a yellow tint and night vision disturbance, at higher doses, alongside the testosterone suppression and liver enzyme shifts seen with other SARMs. As an investigational, unapproved compound that is WADA-prohibited and frequently sold mislabeled or contaminated, harm reduction focuses on third-party verification, pre-and-on-cycle bloodwork (LH, FSH, total T, lipids, ALT/AST), and a PCT plan.

## Pharmacokinetics

- **Model tier:** advanced
- **Half-life:** 0.2 days (3.9000000000000004 hours)
- **Cmax:** 513.45 ng/mL
- **Tmax:** 0.0 days
- **Bioavailability:** 50%

## Dosing

- **Default dose:** 25 mg
- **Typical range:** 12.5–50 mg
- **Units:** ng/mL

## Harm reduction

- **Aromatizes:** No
- **Hepatotoxicity:** mild
- **Injection frequency:** Oral, 2×/day
- **Interaction notes:** Known vision side-effect (yellow tint, night blindness) at higher doses.

## Detection time (anti-doping)

- **Window:** 3–6 days post-last-dose
- **Target metabolite:** Andarine glucuronides + sulfate conjugates
- **Assay:** LC-HRMS/MS
- **Notes:** Limited controlled human excretion data. Glucuronides detectable for days.

## Source

- **Label:** Andarine PK (canine)
- **URL:** https://www.sciencedirect.com/science/article/abs/pii/S0022286019310646
- **Notes:** Canine data, likely inaccurate in humans.

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**Plot:** https://anabolicdex.com/plot?compound=andarine