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Possible Carcinogen Found in Diabetes Drugs

FDA loosens impurity limits to avoid drug shortage

Diagnostic form with diagnosis diabetes type 2.
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A cancer-causing impurity was found in samples of sitagliptin, a common drug used to treat type 2 diabetes, the Food and Drug Administration (FDA) announced.

“Quantifiable levels” of a nitrosamine, Nitroso-STG-19 (NTTP), was detected by pharmaceutical manufacturer Merck in several of its brand-name diabetes medications that contain sitagliptin as an active ingredient, including Januvia, Janumet and Steglujan, it told AARP.

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To avoid a shortage of the drug, the FDA loosened the acceptable daily limit of NTTP from 37 nanograms to 246.7 nanograms. The agency did not cite Merck or any other drug manufacturer in its statement.​

FDA scientists determined that a temporary exposure of NTTP of up to 246.7 nanograms a day “presents minimal additional cancer risk when compared to a lifetime of exposure to NTTP at 37 nanograms a day,” the agency said. ​

Patients who are prescribed any form of sitagliptin are advised to speak with their health care provider before deciding to stop taking the medication, because of the need to control their blood sugar levels, the FDA recommended. ​

Merck said in an email statement that it has “implemented additional quality controls to ensure our portfolio of sitagliptin-containing products meet health authorities’ interim acceptable NTTP limits for continuing distribution.” ​

The company said, “We remain confident in the safety, efficacy and quality of our sitagliptin-containing medicines.”​​

What is NTTP?

​NTTP belongs to a class of compounds called nitrosamines. Some are classified as probable or possible carcinogenic substances. Although there is no data available to evaluate the cancer-causing potential of NTTP, the agency said it used information available on other nitrosamines that are similar to NTTP to calculate its lifetime exposure limit.

Nitrosamines are present in water and foods such as cured and grilled meats, dairy products and vegetables. Although everyone is exposed to some level of nitrosamines, the FDA set an internationally recognized acceptable daily intake limit for the impurity. The agency previously recommended that drugs containing levels above the acceptable daily intake limit be recalled by the manufacturer as appropriate.​

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