What to know about nitrosamine, the cancer-causing ingredient behind Pfizer's recent drug recalls

• Nitrosamines are classified as potential cancer-causing agents.
• The chemicals have been found in several prescription drugs in recent years, prompting recalls.

Several investigations in recent years have prompted the recall of prescription drugs contaminated with a potential carcinogen known as nitrosamine.

The latest recall related to nitrosamines, a class of compounds thought to cause cancer, came last week from Pfizer. On Wednesday, the pharmaceutical giant announced a voluntary recall of some shipments of blood pressure drugs.

Along with six lots of tablets branded as Accuretic, Pfizer recalled five lots of generic versions of the drug (quinapril and hydrochlorothiazide) after they were found to contain an unacceptable amount of N-nitroso-quinapril, a nitrosamine, according to the US Food and Drug Administration.

Small amounts of nitrosamines can be found in water and air, as well as some alcoholic beverages and cured meats, so most people have some level of exposure which poses no risk of cancer, the FDA says. However, scientists believe that taking contaminated drugs over an extended period could elevate a person's risk.

Nitrosamines have become a nightmare for the US drug supply

Previous incidents related to this class of carcinogen include the mass recall of Zantac, a once-popular heartburn medication, after the FDA detected low levels of nitrosodimethylamine (a type of nitrosamine) in the drug in 2019.

Some specific nitrosamines have been linked to cancer and DNA damage, so the whole class of chemicals is considered to have a potential cancer-causing effect in cases of long-term exposure.

The FDA issued its first voluntary recall related to nitrosamines back in 2018, calling it an "impurity" found in some blood pressure medications manufactured abroad. Several medications containing the active ingredient valsartan (and losartan and irbesartan) have since been recalled after they were found to contain levels of nitrosamines above the agency's standard.

However, not all blood pressure drugs containing valsartan formulations have nitrosamine impurities. Chasing down the affected medications has been a challenge that requires global cooperation, said Ed Gump, spokesperson for US Pharmacopeia.

"In the future, this greater scrutiny may lead to the discovery of nitrosamine impurities in other medicines," Gump told Insider. "While these discoveries and the product recalls may seem alarming, this is part of the process to overcome the challenge of nitrosamines and work to eliminate them from our drug supply."

Other commonly prescribed medications that have been linked to nitrosamine impurities include diabetes drugs (metformin) and smoking cessation medicines (varenicline). Most recently, global pharma giant Sandoz recalled 13 lots of oral orphenadrine citrate extended-release tablets, which are prescribed for acute painful musculoskeletal conditions.

Where do nitrosamines come from?

Since 2018, scientists and regulators have been trying to figure out how cancer-causing agents — and suspected carcinogens like nitrosamines — get into pills, and how to keep them out.

Some nitrosamines were once used to make rocket fuel; nowadays, they usually show up as a byproduct of manufacturing drugs or brewing beer, Anna Edney reported for Bloomberg.

Nitrosamines can form through various chemical reactions that occur during drug manufacturing processes, Gump told Insider. Given the many routes of exposure to the contaminant — not only in consumer products, but in the environment — drug manufacturers and regulators have taken a "very conservative approach" to safety limits and recalls, he said.

The FDA set interim limits for nitrosamines in 2018, which were later finalized. In 2021, the agency published updated recommendations on how drugmakers might prevent nitrosamine impurities going forward.

What to do if you're taking drugs that have been recalled

If you have a medication that's been recalled, you should first check the lot number to see if your batch of pills was affected. Most recalls only cover lots that have been confirmed to be contaminated.

You can search for your meds on the FDA's Recalls and Safety Alerts page. To find out if your medication has been recalled, you need to know the manufacturer name (e.g. Pfizer), active ingredient, National Drug Code (NDC), and lot number (usually listed on the bottle next to the expiration date).

If you confirm that your medication has been recalled, stop taking it and consult your doctor to get another prescription. You can also ask your pharmacist for help getting relevant information on potential recalls.

Contact your pharmacist to get this information if you cannot find it or if you have questions about your medication being recalled.