What Compounding Pharmacies Do
Compounding is when a licensed pharmacy combines, mixes, or alters ingredients to create a customized medication for a specific patient — something a mass-manufactured drug can’t always provide (a different strength, a needed allergen-free formulation, and so on). Section 503A of the FD&C Act governs this practice, and one of its core requirements is that the bulk drug substances a compounding pharmacy uses have to meet specific criteria: they need to comply with a USP/NF monograph, be a component of an FDA-approved drug, or appear on FDA’s 503A bulks list.
The Interim Bulks List: Three Categories
- Category 1: nominated with sufficient supporting information and no identified safety concerns — FDA doesn’t intend enforcement action against compounders using these, under specified conditions
- Category 2: nominated with sufficient information, but FDA has identified significant safety risks — FDA would consider enforcement action and publishes the safety concerns it identified
- Category 3: insufficient supporting information for FDA to evaluate at all — not eligible for Category 1 protections
Where the Pharmacy Compounding Advisory Committee Fits In
FDA consults the Pharmacy Compounding Advisory Committee (PCAC) — a panel that includes outside experts — as part of evaluating substances for the official 503A bulks list. PCAC reviews the nominated substance, hears from FDA’s own scientific staff and from public commenters, and votes on a recommendation. That recommendation goes to FDA, which then decides whether to proceed with formal rulemaking to add a substance to the permanent list. The next lesson walks through exactly how this played out for a set of peptides that includes several Signal Library compounds.
✅ Quick Recap
- Section 503A governs pharmacy compounding, including which bulk substances can legally be used
- The interim bulks list sorts nominated substances into three categories based on safety information
- Category 2 means FDA identified a specific safety concern and would consider enforcement action
- The Pharmacy Compounding Advisory Committee reviews nominations and votes on recommendations to FDA