FDA Updates 503A Bulks List Criteria, Tightening API Supplier Qualification Requirements for Compounders

Compounding facilities operating under section 503A of the FD&C Act face a tightening compliance framework as FDA continues its rolling evaluation of bulk drug substances eligible for use in non-sterile and sterile compounding, with direct consequences for API supplier qualification programs and certificate of analysis (CoA) review protocols.

Under the current framework, state-licensed pharmacists and physicians may only compound using bulk drug substances that satisfy one of three conditions: conformance with an applicable USP or National Formulary monograph; status as a component of an FDA-approved drug product where no monograph exists; or explicit inclusion on FDA's 503A bulks list. Every bulk drug substance used must be accompanied by a valid CoA and sourced from an establishment registered with FDA under section 510 of the FD&C Act. FDA has explicitly urged compounders to verify their bulks supplier's registration status, a step that maps directly to supplier qualification procedures under 21 CFR Part 211 and ICH Q10 quality system expectations.

The regulatory history is material for QA teams tracking list evolution. A February 2019 final rule placed six substances on the 503A bulks list, excluded four, and codified the evaluation criteria. A September 2019 proposed rule followed, proposing to add five substances and exclude 26 others; that rulemaking remains open pending final agency action after public comment review. FDA has committed to addressing additional nominated substances on a rolling basis through notice-and-comment rulemaking, meaning the list's composition will continue to shift.

For QA directors managing interim-period risk, FDA's three-category interim policy defines the enforcement posture. Category 1 substances, nominated with sufficient supporting data and not flagged for safety concerns, carry a non-enforcement commitment provided compounders meet specified conditions. Category 2 substances carry identified safety risks; FDA publishes the supporting safety information on FDA.gov when a substance is moved to this category and has signaled it would consider enforcement action for compounding with these materials. A third category addresses substances nominated without sufficient data to permit full evaluation.

The practical compliance read for QA and regulatory leads is straightforward: supplier qualification files must confirm section 510 registration for every bulk drug substance source, CoA review procedures should be mapped against the current list status of each substance, and change-control processes need a trigger for list updates, particularly given FDA's rolling rulemaking cadence.

The September 2019 proposed rule's final disposition, once published, will determine whether 26 substances currently in limbo are formally excluded, at which point compounders relying on the interim policy for those materials will need to reassess their formulation portfolios against the confirmed 503A bulks list.

Source: FDA, Human Drug Compounding via FDA.gov, May 14, 2026.