503A vs. 503B: How Peptides Fit Into the U.S. Compounding Framework in 2026 and Beyond

503A and 503B are not just regulatory jargon — they are the legal infrastructure that determines whether peptide therapies are accessible through licensed medical channels or whether patients are left to navigate the gray market. This is the most comprehensive breakdown of the compounding framework as it relates to peptides: what each designation means, what changed in 2023, what the FDA did in April 2026, and what the July 2026 PCAC meeting means for BPC-157, TB-500, MOTS-c, KPV, Semax, Epitalon, and more.

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