Executive summary
Japan regulates peptides under the Pharmaceutical and Medical Device Act (PMD Act, Act No. 145/1960, substantially amended May 2025, phased through 2028). The PMDA (Pharmaceuticals and Medical Devices Agency) conducts scientific review; MHLW grants marketing authorisations. Approved peptides are prescription-only. Compounding is limited. Research-use-only products are a legal grey area.
Authorities and legal categories
MHLW (Ministry of Health, Labour and Welfare): marketing authorisation, policy.
PMDA: scientific review, GMP/QMS inspections, pharmacovigilance.
Key instruments:
PMD Act (Act No. 145/1960, as amended).
Cabinet Orders and MHLW Ministerial Ordinances.
Guidelines for non-natural synthetic peptides (May 2026).
Approved medicines
Approved peptide medicines include semaglutide (Ozempic, Wegovy — limited approval for weight management), tirzepatide (Mounjaro, Zepbound), insulin analogues, liraglutide (Victoza), teriparatide (Forteo), leuprolide, octreotide, and desmopressin.
Source: PMDA medicines search, https://www.pmda.go.jp
Investigational use
Clinical trials require prior approval under the Clinical Trials Act and PMD Act. The PMDA reviews CTN submissions.
Compounding/manufacturing
Japan has limited pharmacy compounding compared to Western jurisdictions. Most peptide preparations are manufactured products requiring marketing authorisation. Compounding in a pharmacy is generally limited to non-sterile preparations per the Pharmacists Act.
Import
Personal import: MHLW permits individuals to import unapproved medicines for personal use subject to the yakkan (import certificate) system. Quantity limits, controlled-substance restrictions, and requirements for a physician's prescription vary by product. Authorised quantities are generally limited—often up to a 1-month supply—and are evaluated at customs on a case-by-case basis. Carried medicines (accompanying the traveller) and mailed shipments are treated differently; mailed unapproved medicines face higher scrutiny and seizure risk. Visitors and residents have different allowances.
Commercial import: requires a marketing authorisation or a foreign manufacturer accreditation under the PMD Act.
Research-use-only products
A genuine laboratory reagent may fall outside the PMD Act's medicinal-product provisions depending on intended use and claims; other import and chemical rules may still apply. "Research use" labelling does not shield a product marketed for human consumption. A May 2026 MHLW guideline on non-natural synthetic peptides addresses quality requirements for peptide APIs used in research and development.
Enforcement examples and uncertainty
The PMDA and MHLW have not issued a specific peptide enforcement statement, but import customs routinely checks peptide shipments.
Uncertainty: the boundary between "research chemical" and "unapproved medicine" under the PMD Act has not been extensively litigated at scale.
Practical interpretation limits
This is general regulatory research, not legal advice. Classification can turn on composition, claims, intended use, route, supplier role, and facts not captured by a product name.
Primary sources
PMDA. https://www.pmda.go.jp
MHLW. https://www.mhlw.go.jp
PMD Act (English translation). https://www.japaneselawtranslation.go.jp
MHLW Guideline on Non-Natural Synthetic Peptides (May 2026). https://www.mhlw.go.jp (search "peptide guideline").