A drug manufacturer has recalled multiple lots of a type of blood pressure medication due to carcinogenic impurities, according to the Food and Drug Administration (FDA).

Appco Pharma LLC is recalling 175,061 bottles of 1-milligram, 2-milligram, and 5-milligram dosages of prazosin hydrochloride capsules, the FDA said in a March 31 report, providing a list of expiration dates and lots for the drugs.

A U.S. government website, MedicinePlus, says that prazosin hydrochloride, sometimes sold under the Minipress or Minipress XL brands, can be used to treat high blood pressure. It’s classified as an alpha blocker, which is a drug that can relax blood vessels for better flow.

Prazosin hydrochloride has also been used off-label to treat posttraumatic stress disorder (PTSD) in some individuals, according to health officials.

The ongoing recall by Appco Pharma, which did not issue a press release, was due to a “cGMP deviation: detection of Nitrosamine Drug Substance-Related Impurities, N-nitroso-prazosin impurity C (NNP) above acceptable limits.”

Nitrosamines are chemical byproducts that are found in some medications, according to federal officials. They have been found to have carcinogenic properties, meaning they may increase the chance of people developing cancer.

The notice didn’t say why the recalled medications contained nitrosamine impurities above acceptable levels. A website that includes details about nitrosamine impurities in medications on the FDA’s website says there are several reasons the carcinogens may be present.

The FDA labeled it a Class II recall, which is when “use of or exposure to a violative product may cause temporary or medically reversible adverse health consequences or where the probability of serious adverse health consequences is remote.”

In recent years, the FDA has recalled or advised companies to recall drugs due to the presence of nitrosamines, including some lots of prazosin hydrochloride capsules that were recalled by Teva Pharmaceuticals in October.

The agency has said that nitrosamines can be found in a variety of drugs and in foods, especially grilled meats, dairy products, and vegetables. Almost everyone is exposed to some level of the organic compounds, it says.

“Nitrosamine impurities may increase the risk of cancer if people are exposed to them above acceptable levels and over long periods of time,“ the FDA says, ”but a person taking a drug that contains nitrosamines at-or-below the acceptable daily intake limits every day for 70 years is not expected to have an increased risk of cancer.”

The FDA adds that patients who are taking medications that have possible nitrosamine impurities shouldn’t stop taking them and instead speak to a health care professional.

In 2020, Appco Pharma LLC, the recalling company, issued a voluntary recall of ranitidine hydrochloride capsules, which are used for treating gastric ulcers, due to an elevated presence of nitrosamines.