Following last year’s recall of a host of blood pressure medications containing the potentially dangerous chemical nitrosamine, the U.S. Food and Drug Administration (FDA) has published a list of 40 types of valsartan blood pressure drugs that are free of the contaminant.

The agency released the list after an increasing number of generic blood pressure medications made outside the U.S. were found to be contaminated with probable human carcinogens.

Although the FDA has vetted the 40 drugs on its list, pharmacies won’t necessarily only stock those items, said Dr. Guy L. Mintz, speaking to WebMD. Dr. Mintz is the director of cardiovascular health and lipidology at the Sandra Atlas Bass Heart Hospital in Manhesset, N.Y.

Mintz said patients who use mail-order pharmacies may receive generic medicines that have changed manufacturers since their last refill.

Variety of Contaminated Valsartan Found

Valsartan is the generic name for Diovan, which itself has been deemed free of contaminants. The problem, however, is not with valsartan but with the manufacturing process.

Trace amounts of NDMA (N-nitrosodimethylamine), a probable human carcinogen that occurs during some manufacturing processes, were detected in valsartan pills from Zhejiang Huahai Pharmaceutical Co. Ltd. After this discovery, many brands of valsartan and valsartan-based combination medications were recalled.

NDMA can be unintentionally created through certain chemical reactions during the manufacturing of pesticides, rubber, tires and dyes, according to the Environmental Protection Agency (EPA). The contaminant can also be an unintended byproduct when water is disinfected at water treatment plants that use chloramines. In laboratory tests, NDMA has been found to initiate tumors in the liver, respiratory tract, kidneys and blood vessels of mice and rats.

AurobindoPharma USA, Inc. and Acetris Health LLC voluntarily recalled 126 lots of valsartan and valsartan/amlodipine combination pills due to a similar contaminant, NDEA (N-nitrosodiethylamine). NDEA, which occurs naturally in some foods, water, air pollution and manufacturing processes, also is classified as a probable human carcinogen. The affected lots of valsartan and valsartan-containing combination products were made in India.

Valsartan belongs to a class of medications known as angiotensin II receptor blockers (ARBs) which block the protein hormone angiotensin from constricting blood vessels, raising blood pressure.

FDA Provides Guidelines for NDMA Exposure

Fortunately, the risk of developing cancer from tainted valsartan is very slight. The FDA says that “0.096 micrograms of NDMA per day is considered reasonably safe for human ingestion based on lifetime exposure.”

The agency theorized that given 8,000 patients taking the highest dose of NDMA-contaminated valsartan daily for four years, one additional case of cancer over a lifetime could be diagnosed. Most people take less than the 320 mcg maximum dosage, which means their risk of cancer would be lower than the FDA’s worst case scenario.

Several patients have already filed lawsuits alleging breach of warranty claims, common-law fraud, state-level consumer protection law violations and product liability laws.

The FDA continues to test valsartan and valsartan-based combination blood pressure pills for contaminants.