Popular diabetes drug found to contain potential cancer causing ingredient

A widely used diabetes drug that’s the active ingredient in Merck & Co.’s Januvia has been found to be contaminated with a potential carcinogen.

An impurity called a nitrosamine was found in some samples of the drug, which has the chemical name of sitagliptin, the US Food and Drug Administration said Tuesday. The agency said it was permitting drugmakers to continue to sell sitagliptin with higher-than-allowed levels of nitrosamine in order to avoid shortages.

Merck didn’t immediately respond to a request for comment. It was unclear whether any tainted ingredients were found in the company’s products.

Januvia is Merck’s third best-selling drug with $3.3 billion in sales last year, according to Bloomberg data. Sitagliptin is also a component in Merck’s Janumet, which had revenue of almost $2 billion last year.

Sitagliptin, used to control high blood sugar in patients with type 2 diabetes, is one in a string of medications found to be contaminated with nitrosamines since 2018.

Another popular diabetes drug called metformin was among those affected, along with certain blood pressure pills and Pfizer Inc.’s smoking cessation drug, Chantix.

Four years ago, pharmaceutical companies discovered that some blood pressure pills were tainted with N-Nitrosodimethylamine, or NDMA, kicking off a years-long examination of commonly used medicines that uncovered several instances of contamination.

NDMA likely can increase the risk of cancer after prolonged exposure at the levels detected in the drugs.

The nitrosamine discovered in sitagliptin is called Nitroso-STG-19, or NTTP.

“Although there are no data available to directly evaluate the carcinogenic potential of NTTP, FDA used information available on closely related nitrosamine compounds to calculate lifetime exposure limits for NTTP,” the agency said.

The FDA allows 37 nanograms per day of nitrosamine in a drug, though it is allowing up to 246.7 nanograms in sitagliptin to avoid shortages. The agency said that its calculations show the difference in cancer risk is minimal.

The agency recommended patients continue on their sitagliptin drugs until they talk to a health-care provider.

“FDA recommends prescribers continue to use sitagliptin when clinically appropriate to prevent a gap in patient treatment,” according to the agency.

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