Professional Compounding Centers of America (PCCA) received a warning letter for significant current good manufacturing practice (CGMP) violations involving drugs and active pharmaceutical ingredients (APIs) discovered during an October 2019 inspection of their Houston, Texas facility. The FDA identified multiple compliance failures including receipt and distribution of adulterated drugs from suppliers with CGMP violations, failure of their glycerin USP product to conform to compendial standards for identity and purity, and inadequate manufacturing methods and controls for their glycerin API. Additionally, finished drug products including tramadol HCl, fentanyl citrate, buprenorphine HCl, and morphine sulfate were found to be misbranded. The warning letter was amended and reissued on January 27, 2021, following PCCA's November 2019 response to FDA Form 483 observations.