Why Is Losartan Being Taken Off the Market?

Losartan is not being permanently removed from the market. What has happened, starting in late 2018 and continuing through 2019, is a series of targeted recalls of specific losartan batches after regulators discovered they were contaminated with nitrosamines, a family of chemicals linked to cancer at sustained high exposures. The confusion is understandable: the recalls were large, they hit multiple manufacturers, and they followed on the heels of an even bigger recall of a related blood pressure drug, valsartan. But losartan itself remains an approved, widely prescribed medication. The story is really about manufacturing contamination, not a flawed drug.

What Triggered the Recalls

The trouble started not with losartan but with valsartan. In mid-2018, European regulators discovered that certain batches of valsartan, another blood pressure medication in the same drug class (angiotensin receptor blockers, or ARBs), contained an impurity called NDMA. NDMA belongs to a group of chemicals called nitrosamines, which are probable human carcinogens. Regulators quickly expanded their investigation to other ARBs, and by early 2019, contaminated batches of both losartan and irbesartan had been identified and recalled as well.¹ The recalls affected products from multiple generic manufacturers, which made the situation feel enormous to patients who suddenly saw their specific pill bottles on recall lists.

The FDA estimated that patients could have been exposed to the contaminated products for roughly four years before the issue was caught, after manufacturers had made changes to how they produced the active ingredients. The agency speculated that up to two million people may have taken medications containing these carcinogenic impurities, and estimated that roughly one additional cancer case might result for every 8,000 people who took the highest dose of an affected lot over that four-year window.² That risk, while not zero, is small on an individual basis. It is roughly comparable to the background cancer risk most people accumulate from everyday exposures. But at a population scale, affecting millions of patients, regulators treated it seriously.

How Nitrosamines Got Into the Pills

Nitrosamines are not an ingredient anyone intended to put into a blood pressure pill. They formed as unwanted byproducts of chemical reactions during manufacturing. The root cause traces back to changes in how generic manufacturers synthesized the active pharmaceutical ingredients. In the case of valsartan and related ARBs, a modified manufacturing process replaced one reagent (tributyltin azide) with sodium azide, and used dimethylformamide (DMF) as a solvent. Leftover sodium azide was then neutralized with sodium nitrite. The problem was that dimethylamine, present either as an impurity in the DMF solvent or formed during the reaction itself, could combine with nitrite under those conditions to produce NDMA.³

In losartan products specifically, the impurities found were not limited to NDMA. Testing also detected NDEA (N-nitrosodiethylamine) and NMBA (N-nitroso-N-methyl-4-aminobutyric acid), along with azido impurities that are a separate category of concern.⁴ The variety of contaminants reflects the complexity of the chemical synthesis: different reaction conditions, different solvents, and different impurity profiles in starting materials can all generate different nitrosamines. Stability studies have also shown that losartan tablets containing nitrosamine impurities can degrade more quickly under certain conditions like light exposure and acidic environments, meaning the problem could worsen during storage.⁵

The global pharmaceutical supply chain made detection harder. Active ingredients for generic drugs are often synthesized in one country, processed or packaged in another, and sold in a third. Roughly 80 percent of the active ingredient manufacturers for generic drugs are located in China and India, and the finished medications may pass through multiple intermediaries before reaching a pharmacy shelf.⁶ That fragmentation means a single manufacturing change at one facility can ripple across dozens of brand names and markets before anyone notices.

Why Nitrosamines Are Concerning

The reason regulators moved so aggressively on these recalls has to do with how nitrosamines interact with DNA. NDMA, the most commonly detected contaminant, is classified as a probable human carcinogen. When the body metabolizes NDMA, it produces reactive molecules that can chemically attach to DNA bases, forming what are called methyl adducts. These adducts distort the genetic code and, if the cell’s repair machinery does not catch and fix them, can lead to mutations. The specific DNA lesion most associated with NDMA exposure is one called 3-methyladenine, which the body’s repair enzyme attempts to remove. But the repair process itself generates single-strand DNA breaks that can be toxic or mutagenic on their own.⁷

It is worth emphasizing that this damage is dose-dependent and probabilistic. A small amount of nitrosamine exposure from a contaminated pill taken for a few months is not the same as chronic high-dose exposure. You encounter trace nitrosamines from grilled meats, beer, tobacco smoke, and even drinking water. The concern with pharmaceutical contamination was the sustained daily exposure over years in patients who had no way of knowing their medication was affected. Regulatory agencies set acceptable daily intake limits for nitrosamines in medications at very low thresholds, typically in the range of nanograms per day, to keep the lifetime cancer risk extremely small.

Did Cancer Rates Actually Rise Among People Who Took Contaminated Pills

This is the question patients care about most, and the evidence so far is somewhat reassuring for losartan specifically. After the recalls, researchers analyzed adverse event reports submitted to the FDA. They found that cancer reporting signals were highest for valsartan, with one-year post-recall cancer reports roughly two-fold higher than for losartan. The changes in cancer-related reporting for losartan and irbesartan were only about 20 to 30 percent higher compared to control exposures, while valsartan’s were roughly three-fold higher.⁸ This does not mean losartan contamination was harmless, but it suggests the extent of contamination varied significantly between drugs and manufacturers.

A separate meta-analysis of randomized trials looked at whether ARBs as a drug class carry any inherent cancer risk beyond the contamination issue. The researchers found that in trials where average cumulative exposure exceeded three years, there was a statistically significant excess of new cancers in the ARB group compared to controls: about 7.3 percent versus 6.2 percent.⁹ This finding predates the contamination issue and raises a separate question about whether the drug class itself has a small effect, though many researchers consider the signal too small and inconsistent to draw firm conclusions. For the average patient, the cardiovascular benefit of taking an ARB when prescribed far outweighs these uncertain signals.

What Happened to Losartan Prescriptions After the Recalls

Despite the alarming headlines, losartan prescriptions did not collapse. When valsartan was recalled first in July 2018, prescribers actually shifted patients toward losartan and irbesartan as substitutes. Per-prescriber valsartan fills dropped by 57 to 59 percent, while losartan and irbesartan fills rose to compensate. Overall ARB prescribing barely changed.¹⁰ When losartan and irbesartan themselves faced recall notices in early 2019, some switching to unaffected ARBs did occur, but the overall usage trends for losartan in the United States remained essentially unchanged.¹¹

From a spending perspective, the recalls did not cause a noticeable spike in costs for patients or insurers. A national study found that insurer drug spending, patient out-of-pocket costs, and generic prescription fill rates all stayed within about 5 percent of their pre-recall levels.¹² The system absorbed the shock partly because losartan is one of many ARBs on the market, and unaffected lots from other manufacturers could fill the gap.

If Your Losartan Was Recalled, What Should You Have Done

The FDA’s guidance was consistent throughout the recalls: do not stop taking your blood pressure medication without talking to your doctor. Uncontrolled high blood pressure poses its own serious, well-documented risks, including stroke and heart attack. The cancer risk from the contamination was small and probabilistic; the risk from abruptly stopping blood pressure treatment is acute and potentially life-threatening. The appropriate response was to check the FDA’s recall list for your specific manufacturer and lot number, and if your pills were affected, work with your prescriber to switch to an unaffected lot or an alternative medication.

For patients who switched to other ARBs, the transition generally went smoothly. Studies tracking patients moved from losartan to candesartan, for instance, found that blood pressure control was maintained or even slightly improved. One primary care study found a small but significant blood pressure reduction after switching, with no adverse events attributed to the change, and nearly all patients remained on the new medication two years later.¹³ A separate study in Japanese patients with morning hypertension found that switching from standard-dose losartan (or other ARBs) to candesartan produced significant reductions in both morning and office blood pressure readings.¹⁴ The point is not that candesartan is necessarily better than losartan, but that if your specific losartan product was recalled, equally effective alternatives existed and the switch was not medically risky.

The Broader Nitrosamine Problem in Pharmaceuticals

The ARB recalls were the most dramatic, but they turned out to be the tip of a much larger iceberg. Once regulators started looking for nitrosamine contamination more carefully, they found it in other commonly used medications as well, including the heartburn drug ranitidine, the diabetes medication metformin, and the ulcer drug nizatidine.¹⁵ Ranitidine (sold as Zantac) was eventually pulled from the market entirely in 2020, not because of manufacturing contamination, but because the molecule itself appeared to be inherently unstable and could generate NDMA over time, especially when stored at higher temperatures. Losartan’s situation was fundamentally different: the drug molecule is fine, but certain manufacturing processes introduced the contaminants.

The pharmaceutical industry responded by developing much more sensitive analytical methods to detect trace nitrosamines. Laboratories can now quantify NDMA, NDEA, NMBA, and other nitrosamines in losartan drug products at concentrations as low as 0.005 parts per million, well below the FDA’s acceptable intake limits.¹⁶ These screening methods can also catch unexpected impurities that were not originally on anyone’s radar, adding an extra layer of protection against future contamination events.⁴ Regulators in the US, EU, and elsewhere have since required manufacturers to test for nitrosamines across a wide range of drug products, not just ARBs, and to demonstrate that their manufacturing processes do not generate these impurities above acceptable thresholds.

Why the Confusion Persists

Several years after the original recalls, “losartan recall” remains one of the most searched terms related to this medication. Part of the reason is that recalls continued to trickle in over many months. It was not a single announcement but a rolling series of notices affecting different manufacturers, different lot numbers, and different dosage strengths. Each new notice generated a fresh wave of news coverage, creating the impression that the problem was getting worse rather than being methodically cleaned up.

Another factor is that many patients conflated the losartan recalls with the ranitidine withdrawal. Ranitidine was permanently removed from the market because the drug itself was the problem. Losartan was never in that category. The FDA’s concern was always about specific contaminated batches, not about losartan as a molecule. Clean losartan products continued to be manufactured and sold throughout the recall period and remain available today. If your pharmacy currently fills a losartan prescription, that product has been tested against the post-recall nitrosamine limits and meets current regulatory standards.

The episode also exposed a communication gap between regulators and patients. The FDA published detailed lot-specific recall information, but the average person taking a small white pill every morning was unlikely to check their bottle against an online database of affected NDC codes. Doctors’ offices were sometimes slow to proactively contact affected patients. In some cases, patients only learned about the recalls from news headlines, which tended to emphasize the cancer angle without providing the contextual risk numbers. The result was a lot of anxiety that was disproportionate to the actual threat for any individual patient, though entirely understandable given the circumstances.

How Generic Drug Quality Oversight Has Changed

The nitrosamine crisis forced a broader reckoning with how generic drugs are manufactured and monitored. Before 2018, regulators largely trusted that manufacturers would follow good manufacturing practices and that routine inspections would catch problems. The ARB contamination revealed gaps in that system: the manufacturing change that introduced nitrosamines had been in place for years before anyone detected it. Finished-product testing at the time was not designed to look for nitrosamines because nobody expected them to be there.

Since then, the regulatory approach has shifted toward requiring manufacturers to proactively assess nitrosamine risk across their product lines. Drug makers must now evaluate whether their synthesis routes, solvents, reagents, or storage conditions could generate nitrosamines, and test accordingly. The FDA and European Medicines Agency have both published detailed guidance documents outlining acceptable limits for specific nitrosamines and the analytical methods manufacturers should use. For patients, the practical takeaway is that the losartan you get from a pharmacy today has undergone more rigorous impurity screening than the losartan of 2017. The contamination crisis was real, but it also prompted the kind of systemic improvement that makes the current supply safer than what came before.