Peptide terminology and evidence glossary

The vocabulary used across the library, defined once, with the distinctions that matter.

Why this matters

• The vocabulary in this area does a lot of quiet work. Approved, compounded, investigational and research use only sound like points on a single scale, and they are not — they are separate categories with different oversight.
• Having the terms in one place means you can read any page here, or anywhere else, and check what a word is doing in a sentence. Precision here is not pedantry; the difference between two of these words is often the whole meaning of a claim.

Regulatory vocabulary

An approved drug product has been reviewed by the FDA and authorised for a specific named indication. The approval attaches to that product and that indication together, which is why the same product used for a different purpose is described as off-label: lawful for a clinician to prescribe, but not evaluated by the FDA for that use.

A compounded preparation is made by a licensed pharmacy under a separate legal framework. It is not an approved product and is never described as one. An investigational substance is studied under an Investigational New Drug application rather than marketed. A product labelled research use only is not intended for human use and sits outside the prescription supply chain entirely. A cosmetic ingredient is regulated differently again, and cosmetic status does not support a claim about treating a condition.

Evidence vocabulary

Preclinical describes laboratory and animal work conducted before human testing. A clinical trial is a study in people, and its strength depends on whether it was controlled, randomised, blinded, how large it was, and how long it followed participants. An observational study measures what happens without assigning the intervention, which makes confounding harder to exclude.

A systematic review gathers and appraises the available studies on a question and is generally stronger than any single study, though only as strong as the studies it found. An endpoint is what a study measures; a surrogate endpoint is a stand-in for the outcome that actually matters. Statistical significance indicates that a difference is unlikely to be chance, and says nothing at all about whether the difference is large enough to notice.

Pharmacology vocabulary

A receptor is the protein a signalling molecule binds to. An agonist activates it; an antagonist blocks it. Pharmacokinetics describes what the body does to a substance — absorption, distribution, metabolism and clearance — while pharmacodynamics describes what the substance does to the body.

Half-life is how long it takes for half a substance to clear, which shapes how long a signal persists. Bioavailability is the proportion that reaches circulation in active form, and is the reason many peptides are injected rather than swallowed. An interaction is a change in one substance's effect or exposure caused by another.

Words that get misused

Natural describes origin, not safety, and many potent substances are naturally occurring. Clinically proven has no fixed regulatory meaning and should prompt the question of which study, in whom, measuring what. Pharmaceutical grade is a marketing phrase rather than a regulatory category; the meaningful questions concern who manufactured a product, under what standards, and whether it is a medicine at all.

Third-party tested is likewise not a defined standard. A certificate of analysis reports what one laboratory measured in one sample against the specification it was asked to check, which is useful information and is not equivalent to manufacture under current good manufacturing practice requirements.

Definitions

Approved indication

The specific use for which the FDA has authorised a drug product, based on reviewed human evidence.

Approval is never open-ended; it is tied to the indication that was reviewed.

Off-label use

Use of an approved product for a purpose the FDA has not evaluated for that product.

Compounded preparation

A medication prepared by a licensed pharmacy under a legal framework separate from drug approval.

It is not an FDA-approved product and is not described as one.

Investigational substance

A substance studied under an IND application rather than marketed as a product.

Research use only

A label indicating a product is not intended for human use and sits outside the prescription supply chain.

Surrogate endpoint

A measurement standing in for the outcome that actually matters to a person.

Current good manufacturing practice

The FDA's regulatory requirements governing how drugs are manufactured, tested and controlled.

Certificate of analysis

A laboratory report describing what was measured in a specific sample against a stated specification.

It describes one sample, not a manufacturing standard.

What is reasonably established

• Approved, off-label, compounded, investigational, research-use-only and cosmetic are distinct regulatory situations with different oversight.
• Off-label use of an approved product has not been evaluated by the FDA for that use.
• Current good manufacturing practice requirements are a defined regulatory standard for drug manufacturing.

What is not established

• That terms such as pharmaceutical grade or clinically proven carry any defined regulatory meaning.
• That a certificate of analysis for one sample describes the manufacturing standard of a product line.
• That a substance being naturally occurring indicates anything about its safety.

Safety context

• Misreading a regulatory term is a common route to assuming an unapproved product has been reviewed by someone.
• Anti-doping status is separate from medical and regulatory status; substances lawful to prescribe may still be prohibited in competition.
• Suspected harms can be reported to the FDA through MedWatch.

Regulatory framing

This glossary exists so that the categories stay separate wherever they appear. Nothing in it should be read as placing any particular substance in any particular category; that determination belongs to the individual record for that substance.

Frequently asked questions

Is pharmaceutical grade a real regulatory category?

No. It is marketing language with no fixed regulatory definition. The meaningful questions are who manufactured the product, under what standards, and whether it is a medicine at all.

Is off-label use the same as unapproved?

They overlap but differ. Off-label use involves an approved product used for a purpose the FDA has not evaluated. An unapproved substance has no approved product status for any use.

Does a certificate of analysis mean a product is safe for human use?

No. It reports what one laboratory measured in one sample against a requested specification. It says nothing about whether the product is a medicine or how the wider product line is manufactured.

Sources

• Understanding Unapproved Use of Approved Drugs "Off Label" — U.S. Food and Drug Administration
• Human Drug Compounding — U.S. Food and Drug Administration
• Compounding and the FDA: Questions and Answers — U.S. Food and Drug Administration
• Investigational New Drug (IND) Application — U.S. Food and Drug Administration
• Current Good Manufacturing Practice (CGMP) Regulations — U.S. Food and Drug Administration
• Is It a Cosmetic, a Drug, or Both? (Or Is It Soap?) — U.S. Food and Drug Administration
• The Prohibited List — World Anti-Doping Agency

This page is educational. It is not medical advice, not a prescription, and nothing here can be ordered. Compounded preparations are not FDA-approved. To ask a physician about your own situation, visit goal.md/peptides/connect or call or text 314-907-3103.

Medically reviewed by Michael Fitch, MD. Compliance review by Michael Mimlitz, MD. Last reviewed 2026-08-15.