Sources: U.S. Food and Drug Administration (FDA) Compounding and the FDA (503A & 503B guidance) FDA warning letters on unapproved peptide products National Institutes of Health (NIH) PubMed FDA Moves to Reevaluate Several Peptides American Med Spa Association FDA Issues 115 Warning Letters to Retailers Selling Unauthorized E Cigarettes Buchanan Ingersoll & Rooney PC Gray Market Peptides: So Much Hype, So Little Data