After the FDA noticed a possible carcinogen in popular diabetes med metformin last year, a parade of recalls ensued. Now, less than a week into 2021, one of the drugmakers caught up in the recent spate of withdrawals is pulling another lot of its product.

Nostrum Laboratories on Monday said it was voluntarily recalling one lot of 750-mg extended-release metformin tablets after samples were found to contain higher-than-allowed levels of N-nitrosodimethylamine (NDMA). The move extends a metformin recall Nostrum issued in November, the FDA said.  

The company didn’t specify how many bottles were in the affected lot, and a Nostrum Labs spokesperson was not immediately available for comment. Each bottle contains 100 tablets, according to the FDA, and carried an expiration date of July 22. They were distributed nationwide to wholesalers.

Monday’s metformin recall comes after the Missouri-based company pulled two lots of the same extended-release metformin product, also due to high levels of NDMA in samples. To date, the company says it hasn’t received any reports of side effects related to the suspect lots.

Nostrum is hardly alone on the FDA’s metformin recall list, and it’s not the first to end up there twice, either. The agency in May asked five generics makers—Apotex, Amneal, Lupin, Marksans and Teva—to pull their extended-release metformin products after detecting abnormally high levels of NDMA in samples.

In July, Lupin pulled all remaining lots of its extended-release metformin, while Marksans initially targeted one lot of 500-mg pills before yanking an additional 76 lots in October.

New Jersey’s Bayshore Pharmaceuticals, for its part, pulled one lot each of its 500- and 750-milligram extended-release metformin in August after the FDA raised similar carcinogen concerns. Sun Pharma joined the parade the following month, recalling one lot of its metformin product Riomet ER, which covered 747 bottles of the drug that were pegged to expire in October 2021.