Educational only. Not medical or legal advice. This site summarizes public U.S. government statements as of October 22, 2026. It does not sell, recommend or endorse any product, and it does not give dosing information. Talk to a licensed clinician about any medicine, and check the linked FDA pages for the latest version.
- 503A
- The section of the FD&C Act covering compounding by state-licensed pharmacists and physicians. [FDA]
- 503B / outsourcing facility
- A compounder that registers with FDA as an outsourcing facility under section 503B and must re-register annually. [FDA]
- Bulk drug substance
- The active ingredient a compounder starts from; 503A compounders may use only certain bulk substances. [FDA]
- Category 1 / 2 / 3
- FDA's interim categories for nominated 503A bulk substances; category 2 means FDA identified significant safety risks. [FDA]
- CGMP
- Current good manufacturing practice requirements; outsourcing facilities are not exempt from them. [FDA]
- Close-out letter
- A letter FDA issues after verifying that warning-letter violations were corrected. [FDA]
- Compounded drug
- A drug made by combining or altering ingredients; compounded drugs are not FDA-approved. [FDA]
- Essentially a copy
- A compounded drug that is essentially the same as a commercially available approved drug; restricted under 503A and 503B. [FDA]
- Form FDA 483
- The form listing inspection observations; FDA's outsourcing table shows whether one was issued. [FDA]
- Peptide
- For FDA regulatory purposes, an amino acid polymer of 40 or fewer amino acids. [FDA CDER MAPP 5016.3]
- Protein
- An alpha amino acid polymer with a specific defined sequence greater than 40 amino acids. [FDA CDER MAPP 5016.3]
- Warning letter
- FDA notice that it believes there are significant violations of federal requirements. [FDA]