The Food and Drug Administration said traces of a potential carcinogen were found in samples of a popular diabetes drug made by Merck, the latest case in which impurities have been discovered in the top-selling pharmaceutical products.
Millions of people with type 2 diabetes rely on the drug sitagliptin to keep high blood sugar levels at bay. Merck markets the drug as Januvia and Janumet. Last year, sitagliptin generated sales of more than $5 billion for Merck and was the third best-selling product.
Although the impurities were found in some batches, the FDA will allow Merck to temporarily continue selling the drug because the risks are outweighed by the immediate medical needs of patients. “It could be dangerous for patients with this condition to stop taking sitagliptin without first talking to their doctor,” the agency said in a statement.
Merck, which first discovered the contamination and reported it to regulators, said it was trying to address the problem and would be working with health officials around the world. “We remain confident in the safety, efficacy and quality of our sitagliptin-containing medicines,” the company said, adding that it did not anticipate any shortages in the drug, which was first approved by the FDA in 2006.
The impurity known as NTTP belongs to the family of nitrosamine compounds that have been discovered in a number of drugs in recent years. Since 2018, federal agencies have warned the public about nitrosamine contamination in samples of the heartburn drug Zantac, the antibiotic Rifampin and the smoking cessation drug Chantix.
The FDA has described NTTP as a “probable human carcinogen” based primarily on laboratory testing. The agency lacks data to directly assess NTTP’s carcinogenic potential and instead said it used information about a closely related compound to determine exposure limits. Agency scientists have set lifetime exposure to nitrosamine in medications at 37 nanograms per day, although for now it will allow up to 246 nanograms in sitagliptin.
In its statement, the FDA described the additional cancer risk as “minimal.”