February 3, 2023

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Merck diabetes drug Sitagliptin was hit by carcinogenic impurities


Merck diabetes drug Sitagliptin was hit by carcinogenic impurities

Sitagliptin was hit by carcinogenic impurities, and Merck’s blockbuster diabetes drug may cause “recall” and “withdrawal”

The FDA recently said the nitrosamine impurity Nitroso-STG-19 (NTTP) was found in some samples of Merck’s type 2 diabetes blockbuster drug sitagliptin (Januvia).

It is unclear how the NTTP impurity emerged in Januvia, and the FDA did not specify whether Merck or a third-party manufacturer produced the suspect samples.

In order to avoid a shortage of Januvia and provide enough medicines for patients, the FDA will not object to the temporary distribution of sitagliptin NTTP containing more than the acceptable intake limit of 37 ng per day, up to 246.7 ng per day.


With sales of $5.3 billion in 2021, Januvia is Merck’s third-best-selling drug after Keytruda and Gardasil.



Merck diabetes drug Sitagliptin was hit by carcinogenic impurities



NNTPs belong to the class of nitrosamines, some of which are classified as possibly cancer-causing substances based on laboratory tests.

Although no data are available to directly assess the carcinogenic potential of NTTP, the FDA used available information on closely related nitrosamine compounds to calculate lifetime exposure limits for NTTP.


FDA scientists assessed and determined that a single-day maximum of 246.7ng of interim acceptable intake risk posed minimal additional cancer risk compared to lifetime exposure of 37ng per day.


Since 2019, nitrosamine discoveries have plagued dozens of drugs, from generics like popular diabetes drug metformin to Sanofi’s ranitidine (Zantac) and Pfizer’s smoking cessation drug varenicline (Chantix). and other big brands.

The contamination incident has sparked recalls, shortages and full market withdrawals.


In March, Pfizer’s blood pressure-lowering drugs Quinapril/Hydrochlorothiazide (Accuretic) and Propranolol Inderal were recalled in Canada for containing nitrosamines.

In April, another Pfizer blood pressure drug, quinapril (Accupril), was recalled in the United States because of the same problem.


While nitrosamines have proven to be a big problem for the pharmaceutical industry, it has also been suggested that strict tracking procedures could trigger shortages of critical drugs.

There are currently no Januvia shortages listed in the FDA’s virtual database.


Shortages of the drug during Pfizer’s Chantix contamination incident last year prompted the FDA to allow manufacturers to temporarily dispense varenicline tablets containing the impurity N-nitrosovarenicline, exceeding the agency’s acceptable intake of 37ng per day dose limit but below the temporary limit of 185ng per day.

The FDA said last July that it would adjust the rules “until the impurity can be eliminated or reduced to acceptable levels.”


To make matters worse, the FDA even asked drugmakers in April 2020 to withdraw all prescription and over-the-counter ranitidine products from the market.


Going back to Januvia , this appears to be the first place the drug’s nitrosamine problems are.

However, as Zantac, metformin, and Chantix have shown, initial impurity issues are often the harbingers of recalls.


For now, people with diabetes and Merck will have to wait and see what the future holds for Januvia.






Merck diabetes drug Sitagliptin was hit by carcinogenic impurities

(source:internet, reference only)

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