Why have so many blood pressure medications been recalled lately?

Since July, the Food and Drug Administration has announced voluntary recalls of blood pressure and heart medications from Major Pharmaceuticals, Solco Healthcare, Teva Pharmaceuticals Industries and Mylan Pharmaceuticals. Just this week, Prinston Pharmaceuticals recalled one lot of irbesartan and seven lots of irbesartan HCTZ, the company announced in a news release.

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In addition to irbesartan, the drugs valsartan and losartan were found to contain trace amounts of cancer causing impurities. These impurities were traced to factories in China and India that make valsartan ingredients and ship them to generic drug companies throughout the world.

The FDA inspects foreign factories that make drugs for U.S. companies. It was during these inspections the FDA discovered unacceptable levels of N-Nitrosodimethylamine, or NDMA. Further testing revealed the presence of N-Nitrosodiethylamine, or NDEA, in batches of valsartan.

The majority of the recalled drugs were produced in the Zhejiang Huahai Pharmaceutical factory in Linhai, China, USA Today reported, and the FDA issued an import alert, preventing its drugs from being shipped to the United States.

"We still don't understand the complete root cause of this problem," Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research, told USA Today. "I would think these recalls would start dropping off now."