The U.S. Food & Drug Administration has learned that some ranitidine (Zantac) medicines including some products commonly known as the brand-name drug Zantac, contain a nitrosamine impurity called N-nitrosodimethylamine (NDMA) at low levels. NDMA is classified as a probable human carcinogen (a substance that could cause cancer) based on results from laboratory tests. NDMA is a known environmental contaminant and found in water and foods, including meats, dairy products, and vegetables.
Although NDMA may cause harm in large amounts, the levels the FDA is finding in ranitidine from preliminary tests barely exceed amounts you might expect to find in common foods. Until the FDA reevaluates, other over the counter H2 blockers such as famotidine (20 mg), cimetidine (150 mg) or nizatidine (150 mg) are good substitutes for ranitidine (150 mg).