MedicalResearch.com Interview with: [caption id="attachment_57762" align="alignleft" width="150"] Dr. Strauss[/caption] David Strauss, MD, PhD Director, Division of Applied Regulatory Science [caption id="attachment_57763" align="alignleft" width="150"] Dr. Keire[/caption] David Keire, PhD Director, Office of Testing and Research U.S. Food and Drug Administration Center for Drug Evaluation and Research  MedicalResearch.com: What is the background for this study? Response: In 2019, the US Food and Drug Administration (FDA) received a citizen petition indicating that ranitidine, a widely used prescription and over-the-counter drug, contained the probable human carcinogen N-nitrosodimethylamine (NDMA). In addition, the petitioner proposed that ranitidine could convert to NDMA in humans; however, this was based on a small clinical study with limitations and an in vitro study that included high level of supplemental nitrite. In response, the FDA immediately alerted the public and began an investigation. The FDA’s initial research found that the procedures previously used to quantify NDMA were not appropriate for assessing its presence in ranitidine, owing to the use of high temperatures that could convert ranitidine to NDMA during that analysis. New lower-temperature analytical methods found that the amounts of NDMA contained in ranitidine products were 3,000-fold lower than those reported in the citizen petition; however, these lower amounts of NDMA were still above the FDA-acceptable level and could increase over time, prompting the FDA to request the market withdrawal of ranitidine products. The FDA noted, however, that if ranitidine products could be manufactured to control NDMA amounts, they could be allowed back on the market—but additional information would first be needed to understand whether NDMA could form in vivo from ranitidine in humans.