By Jamie Ducharme
Updated: January 30, 2019 8:29 AM ET | Originally published: January 29, 2019

Cynthia Brown had been taking the drug valsartan for about two years when she learned last August that it had been recalled over fears of potential carcinogen contamination. Brown, a writer and patient advocate living near Cincinnati, had been prescribed valsartan to control shortness of breath related to primary pulmonary hypertension, but suddenly she had a whole new concern: cancer.

“I’ve always been very conscientious about my health. I never dreamed I’d be on all these medications, and I’m real funny about what I take,” Brown, 65, says. “Valsartan has made me leery of all medications.”

Brown is just one of the patients affected by a string of drug recalls dating back to last summer. Dozens of batches of generic drugs including valsartan, irbesartan and losartan have been recalled by a variety of manufacturers because they may contain amounts of nitrosamine impurities that exceed current safety standards, the Food and Drug Administration (FDA) announced. Nitrosamine impurities including N-Nitrosodimethylamine (NDMA) and N-Nitrosodiethylamine (NDEA), which are also sometimes found in meat, dairy products, vegetables and water, are considered probable carcinogens, the FDA says.

Valsartan, irbesartan and losartan are angiotensin II receptor blockers (ARBs), which are commonly used to treat high blood pressure and heart failure. Almost 50 million prescriptions for losartan were written in 2016, according to ClinCalc, as well as 8.4 million for valsartan and 3.6 million for irbesartan.

Recalls have been so widespread that there’s now a national shortage of valsartan — causing formulations still on the market to spike in price, according to USA Today — and “other types of products may fall into shortage soon,” according to the statement from the FDA. An FDA representative tells TIME it’s impossible to predict when the valsartan shortage could end or which other drugs may soon be in short supply, but said the agency remains “focused on protecting patients from exposure above the interim intake levels.”

The agency says it continues to investigate how these substances got into ARB drug supplies, and is working to stem the flow of potentially tainted pharmaceuticals from overseas manufacturers. Many of the affected ARBs came from producers in China and India, according to FDA recall notices, and the FDA warned one Chinese manufacturer about “significant” production issues last year.

The FDA also emphasized that the overall risk to consumers is fairly low. FDA scientists estimate that if 8,000 people had been taking the maximum daily dose of valsartan for four years — the length of time affected products may have been on the market — there would only be one cancer case in that population beyond what’s normally expected, according to the statement. Plus, not all ARBs have been affected by the recalls and levels of exposure vary even among recalled supplies, so it’s unlikely that most people have experienced the worst-case scenario, the FDA says.

Dr. G. Caleb Alexander, co-director of the Johns Hopkins Center for Drug Safety and Effectiveness, calls the breadth of the recalls “unusual,” but says they likely don’t point to a larger drug supply issue.

“This is the exception rather than the norm,” Alexander says. “For every one of these market events, think of all of the tens of millions of prescriptions that are dispensed uneventfully. Our pharmaceutical supply chain is remarkably safe in the United States, and these are very rare events.”

Alexander has studied how FDA drug-risk warnings affect future use of medications, and says in this case, there will “without a doubt” be “large reductions” in the use of these drugs, given the recalls and FDA warnings.

But because there are “dozens of tools in the toolbox” when it comes to treating conditions like high blood pressure, Alexander says it’s unlikely that reductions in use of these specific ARBs will lead to population-wide upticks in conditions such as heart attacks and strokes. That is, even if people have to stop taking their normal drugs, they’ll likely be switched to an effective alternative, Alexander says.

“This may be hugely disruptive with respect to [individual] people’s treatments,” Alexander says, “but I would not expect to see any population-level effects.”

Swapping drugs isn’t always easy, however.

Despite the valsartan shortage Brown found herself with a new prescription for the drug this month. Her doctor had initially switched her to losartan, but Brown says it didn’t work well for her. Then they tried irbesartan, but that, too, was recalled. Finally, her doctor suggested valsartan from a manufacturer that has not been affected by recalls — but Brown said on Thursday that she’d learned even that lot of the drug had been recalled. She says she’s consulting her cardiologist “as to, ‘Where do we go from here?'”

Given all the recalls, Brown, who has a family history of cancer, says she’s now concerned about developing it herself, and is staying vigilant about doctor’s appointments and preventative screenings.

“You do worry, because a lot of cancers don’t show themselves until they’re in the late stages. I pray about it, but I’m still human, so I worry about it,” Brown says. “You wonder what’s truly in [these drugs].”

Write to Jamie Ducharme at jamie.ducharme@time.com.

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