In the summer of 2019, an online pharmacy detected a link between Zantac and the carcinogen NDMA during routing batch testing. Shortly thereafter, the pharmacy filed a petition asking the FDA to recall all products containing ranitidine. Around that time, Stanford University also discovered that NDMA contamination of ranitidine was the result of the inherent instability of the ranitidine molecule. In other words, the basic generic chemical component of Zantac appeared to break down over time into the cancer-causing substance, NDMA. The research suggested that the longer Zantac sits on a shelf, the more likely it is to generate very high and dangerous levels of NDMA in the body, particularly if it is stored at higher temperatures.