A wave of recalls ensued after Valisure, then a pharmacy company that regularly tests medications for impurities, indicated the presence of nitrosamine in ranitidine, an ingredient in the heartburn drug Zantac. Valisure petitioned the F.D.A. to broaden testing after ranitidine was found to have a type of nitrosamine called N-nitrosodimethylamine, or NDMA, which is considered a probable carcinogen.

Drugs such as metformin, for people with diabetes, and Chantix, for those trying to quit smoking, have also faced recalls related to probable carcinogens.

Accuretic has relatively few users: About 1,300 people took it in 2020. Its generic formulation has more, about 192,000 users, according to data from IQVIA, an analytics company. The generic drug comprises the ingredients quinapril and hydrochlorothiazide and generated about $4.7 million in sales in 2020, IQVIA data show.

Pfizer said in a news release that it was not aware of any adverse events related to the Accuretic recall. It said the benefits of taking the drug outweighed the risks, adding that the drug lowered blood pressure and reduced the risk of strokes and heart attacks. The company advised patients to talk to their doctors about alternative treatment options.