Compounding, Nonprescription/BTC Products, and Special Distribution Channels
503A versus 503B
The dividing question is whether the preparation is patient-specific and prescription-based. A 503A traditional compounder is a licensed pharmacy or federal facility that compounds on a patient-specific prescription or a documented prescriber-established relationship; it must avoid "essentially a copy" of a commercially available product unless a change produces a significant difference for the patient; bulk drug substances must comply with an applicable USP/NF monograph and appear on FDA's 503A bulks list with a certificate of analysis from a registered establishment; out-of-state distribution is capped absent an MOU; and USP <795> (nonsterile), <797> (sterile), and <800> (hazardous) standards apply. A 503B outsourcing facility registers with FDA, follows cGMP, may compound without patient-specific prescriptions, must use substances on the 503B bulks list, and reports adverse events. State boards still regulate the practice.
Nonprescription and behind-the-counter
OTC status comes from an FDA monograph (GRASE) or an NDA switch. Behind-the-counter is not an FDA category; it is a state or federal restriction layered on an OTC product, most notably CMEA pseudoephedrine (logbook, ID, daily and 30-day limits) and age-restricted emergency contraception. Dietary supplements under DSHEA are not FDA-approved.
Special channels
Drug samples move under the PDMA with prescriber requests and no resale. Restricted distribution systems (iPLEDGE, clozapine REMS, limited-distribution products), 340B, mail order, and VA/DOD channels each carry their own documentation duties.
Traps
Compounded preparations still need a label with a beyond-use date. Bulk substance lists differ between 503A and 503B, so a substance legal for one pathway may be illegal for the other.
Rule of thumb
No list, no bulk: if the substance is not on the applicable FDA bulks list, do not compound from bulk.