Epstein, Becker and Green Provides Great Breakdown in Client Alert of three choices compounders will have: 503A, 503B, or manufacturers

• FDCA Section 503A, which exempts state-licensed pharmacies and federal facilities from FDCA new drug approval, good manufacturing practice ("GMP"), and certain labeling requirements: Section 503A is intended for smaller "traditional" compounding operations, which compound in response to prescriptions (or, in limited quantities in anticipation of prescriptions) and are engaged in minimal out-of-state distribution.
   
• FDCA Section 503B, which exempts sterile drug compounders (called "outsourcing facilities") from FDCA new drug approval requirements, as well as some labeling and drug distribution requirements: Outsourcing facilities are subject to GMP requirements and can only compound with drug substances that are on a "clinical need" list established by the U.S. Food and Drug Administration ("FDA").  However, outsourcing facilities can distribute out of state without limitation and can compound large quantities of products on FDA's drug shortage list without prescription.

Compounders that fail to comply with one of these two safe harbors would potentially be subject FDA enforcement; FDA would presumably argue that the compounder was, in fact, a drug manufacturer that was marketing unapproved new drugs and violating various provisions of the FDCA.
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