Accuretic tablets are taken to treat hypertension and high blood pressure in order to reduce the risk of heart attacks or strokes. The pill, distributed by Pfizer, is being recalled along with two other generic versions of the same drug, distributed by Greenstone.

Pfizer has found Accuretic to have a level of nitrosamine above the acceptable daily intake. While nitrosamine is a fairly common chemical compound and can be readily found in cured and grilled meats, dairy products, and vegetables, high levels and repeated long-term exposure can prove dangerous, according to the U.S. Food and Drug Administration.

Shares in the American pharmaceutical giant have fallen 2.1% since the recall was announced on March 21 after the close of trading.

Nitrosamine and cancer

A systematic review published in the World Journal of Gastroenterology in 2006 found a “positive association between nitrite and nitrosamine intake and gastric cancer.”

Pfizer said that while long-term ingestion of the blood pressure medication can increase cancer risk, “there is no immediate risk to patients taking this medication” and that it was not aware of any reports of adverse events related to this recall. The company added that it “believes the benefit/risk profile of the products remains positive based on currently available data.”

Pfizer told patients currently taking the blood pressure drugs to consult their doctors and pharmacists before discontinuing the recalled medicines or switching to an alternative treatment.

Pfizer Canada recalled Accuretic earlier in March, for the same reason of high nitrosamine levels. In a statement at the time, Canada’s health regulator, Health Canada, said patients could continue to take the medication as prescribed and did not need to return the drug to their pharmacy, but asked patients to consider alternatives.

Accuretic is a combination of two different drugs: quinapril and hydrochlorothiazide. Quinapril is an angiotensin-converting enzyme (ACE) inhibitor that prevents blood vessels from narrowing, while hydrochlorothiazide is a diuretic, which causes a person to urinate more and flushes out sodium in the body. Both drugs are commonly used in other blood pressure medications.

Pfizer announced Tuesday that it would supply up to 4 million courses of its oral COVID-19 treatment to poorer nations, via an agreement with the United Nations Children’s Fund (Unicef). It has also recently announced that it will pause new clinical drug trials in Russia, and CEO Albert Bourla said a fourth COVID-19 vaccine dose may be necessary.