Investigating a class action lawsuit on behalf of individuals who purchased Zantac. The FDA is investigating low levels of a potentially dangerous contaminant in the popular heartburn medication Zantac. As reported by CBS News, The Food and Drug Administration said in a public statement it has detected a "probable" cancer-causing chemical in ranitidine, the generic term for the medication sold as both prescription and over-the-counter treatments to treat stomach acid and ulcers. The federal agency said the carcinogenic ingredient is a type of nitrosamine called N-nitrosodimethylamine, or NDMA. If you purchased Zantac, please fill out the form.