Certain samples of sitagliptin have been found to contain Nitroso-STG-19 (known as NTTP), above the Food and Drug Administration’s (FDA) acceptable intake limit. NTTP belongs to the nitrosamine class of compounds, some of which are classified as probable or possible human carcinogens.

Sitagliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor is indicated as an adjunct to diet and exercise in type 2 diabetes. The FDA has decided to allow the temporary distribution of sitagliptin containing NTTP above the acceptable intake limit of 37ng per day, and up to 246.7ng per day in order to avoid a shortage. 

Agency scientists have determined that exposure to NTTP at these interim acceptable intake levels up to 246.7ng per day presents minimal additional cancer risk compared with a lifetime of exposure to NTTP at 37ng per day. The agency recommends prescribers continue to use sitagliptin when clinically appropriate.

To determine whether drugs should be released for distribution, manufacturers of sitagliptin containing products are being advised to contact the Center for Drug Evaluation and Research’s Drug Shortages Staff when testing shows levels of NTTP that exceed 37ng per day.


FDA works to avoid shortage of sitagliptin following detection of nitrosamine impurity. News release. US Food and Drug Administration. Accessed August 10, 2022. https://www.fda.gov/drugs/drug-safety-and-availability/fda-works-avoid-shortage-sitagliptin-following-detection-nitrosamine-impurity