Methimazole impurity manufacturers?

Do you mean one of these?

- Vendors that supply impurity reference standards for methimazole (for QC/validation and regulatory work)
- Information about the actual impurities that can be present in methimazole API (and where they come from in manufacturing/storage)

If you’re after impurity standards, typical suppliers of pharmaceutical impurity standards include (and you’ll often find methimazole-related standards under related substances):
- Merck MilliporeSigma
- LGC Standards
- VWR/Avantor
- Alfa Aesar
- TCI

If you’re after impurity profiles or regulatory guidance, ICH Q3A/Q3B covers identification and control of impurities in drug substances and drug products, including:
- How impurities are identified and qualified
- How impurity limits are set for methimazole
- Typical methods (e.g., HPLC) and forced-degradation studies to reveal potential impurities

Could you clarify:
- Are you looking for impurity reference standards (and, if so, in which region/country)?
- Or are you seeking information about the impurity profile of methimazole for regulatory purposes?
- Do you have a specific impurity name or designation (e.g., “impurity A,” “N-oxide,” etc.)?

If you share your location and the exact need (standards vs. regulatory impurity data), I can offer more precise supplier options or regulatory guidance.