Why this page exists
Every entry on this site carries a short evidence-strength indicator and an FDA status tag. This page explains exactly what those mean, so a tag like "Preclinical only" reads as information, not just a vague warning label.
The four evidence tiers
Tier 1 — Preclinical only
Studied in cell cultures, tissue samples, or animals (usually rodents). This is real science and often the necessary first step, but effects seen in a rat do not reliably predict effects in a human — dose, metabolism, and biology all differ.
Tier 2 — Early / small human data
At least one human study exists, but it's typically small (a handful to a few dozen participants), short in duration, or focused narrowly on one measurable outcome (like a hormone blood level) rather than a real-world health outcome.
Tier 3 — Human RCTs
Randomized, controlled trials in humans — the design that lets researchers reasonably attribute an effect to the compound itself rather than chance, placebo response, or lifestyle factors. Quality still varies a lot within this tier.
Tier 4 — Regulatory approval
A regulator (FDA, or an equivalent body in another country) has reviewed the full evidence package and approved the compound as a drug for at least one specific indication. This is the highest bar, but it's indication-specific — approval for one use doesn't mean approval, or proven safety, for a different use.
A few important caveats
"Approved" isn't the same everywhere. Several entries here (Semax, Selank, Thymosin Alpha-1) are approved drugs in Russia, China, or elsewhere, but not FDA-approved in the US. We flag exactly which regulator approved what — never assume approval in one country transfers to another.
Evidence tier is not the same as safety. A compound can be Tier 1 (preclinical only) and relatively low-risk, or Tier 1 and genuinely dangerous (see: Dermorphin). Always read the actual Safety & Considerations section on an entry, not just the tier badge.