Glossary
Also written bulks list; bulk drug substance
The interim 503A bulks list is the FDA's working list of bulk drug substances that parties have nominated for use in pharmacy compounding under section 503A. A substance's position on that list, and the category it sits in, is what determines whether a pharmacy may compound with it while the agency's review runs.
The list is interim in a meaningful sense: it is a holding arrangement pending rulemaking, and a substance can enter it, move within it, be removed from it, or leave the process entirely when its nominators withdraw. Removal is not the same as listing, which is the distinction this index returns to most often.