Regulatory categories
Research-only vs prescription medicines — why the terminology matters
Educational explainer on the five regulatory categories that recur in metabolic peptide research: licensed UK prescription medicine, licensed elsewhere but not UK, investigational compound, research-only compound and grey-market product. Why the distinctions matter for safety, legality and evidence.
This page defines five regulatory categories that recur across the metabolic peptide literature: UK-licensed prescription medicine, licensed elsewhere but not in the UK, investigational compound, research-only compound and grey-market product. The distinctions govern evidence standards, legal access routes and the framing used throughout this site. Treating a grey-market vial as equivalent to a licensed medicine, or a phase 2 signal as equivalent to licensed-medicine evidence, is the primary editorial failure mode this classification prevents. Cross-trial comparison has limits — see the linked research-methods primer.
| Category | Meaning | Examples | Evidence level | Legal use |
|---|---|---|---|---|
| Licensed UK prescription medicine | MHRA-licensed for a specific UK indication. Supplied via UK-registered prescriber and UK-registered pharmacy. | Mounjaro, Wegovy, Ozempic, Rybelsus, Saxenda, Victoza, Trulicity. | Pivotal phase 3 trials + outcome trials in the relevant population. | Within licensed indication, on valid UK prescription; off-label is a clinical-judgement decision by a prescriber. |
| Licensed elsewhere, not in the UK | Licensed in another jurisdiction (often US FDA) but not currently MHRA-licensed. | Zepbound (US tirzepatide brand for obesity), Egrifta (US tesamorelin). | Comparable phase 3 evidence to UK-licensed equivalents where applicable; jurisdictional access differences. | UK access requires a UK-legal route; cross-border supply is generally not lawful for personal use. |
| Investigational compound | Active human clinical trials under regulator oversight; not licensed for therapeutic use in any major jurisdiction. | Retatrutide, cagrilintide, CagriSema, survodutide, pemvidutide, mazdutide, cotadutide, orforglipron, danuglipron, MariTide. | Phase 1 / phase 2 / phase 3 in progress; topline-only data common. | Only within an appropriately authorised, ethically approved research setting. |
| Research-only compound | Used in laboratory research but with limited or old human data; not advanced to a regulator-licensed human therapeutic indication. | AOD-9604, HGH Fragment 176-191, CJC-1295, ipamorelin. | Preclinical-heavy or limited older human data. | Laboratory and analytical research only, within institutional governance; not for human therapeutic use. |
| Grey-market product | Product marketed and used as if it were a medicine but supplied outside the regulated pharmacy / prescribing framework. | Compounded GLP-1 vials, unlicensed semaglutide and tirzepatide preparations, counterfeit weight-loss pens. | No regulator-monitored quality control or pharmacovigilance. | Falls outside the lawful supply framework for human use of the implicated active ingredients. |
Why this distinction is the foundation of everything else here
Almost every editorial decision on this site flows from these five categories. UK-licensed medicines get UK prescription-medicine framing; investigational compounds get investigational framing; research-only compounds get research-only framing; grey-market products get explicit warning framing. Mixing the categories — for example, treating a grey-market vial as if it were a Wegovy pen, or treating a phase 2 investigational result as if it were licensed-medicine evidence — is the failure mode we are most actively trying to avoid.
For our full position on this, see how we distinguish licensed medicines from research compounds.
- It is not legal advice. Specific situations may require qualified legal or regulatory guidance.
- It does not endorse any compound for any indication.
- It does not list or rank suppliers in any category.
Related UK regulatory topics
Sources are tagged by class. Regulatory documents, peer-reviewed publications and trial registry records are preferred. Manufacturer disclosures and conference material are accepted where peer-reviewed publication is not yet available; preprints are flagged.
- Regulatory document (MHRA/EMA/FDA)MHRA — Medicines and Healthcare products Regulatory Agency
UK regulatory authority for prescription medicine classification
- Regulatory document (MHRA/EMA/FDA)European Medicines Agency — EPARs
EPARs and product information for approved GLP-1/GIP medicines
- Editorial synthesisSite editorial synthesis — Metabolic Peptides
Editorial comparison of GLP-1 class medicines on this site