When AstraZeneca developed Nexium in the 1990s, the drug was intended to treat various gastrointestinal and indigestion symptoms and conditions. Today, the drug is one of the most popular medications on the market for the treatment of heartburn and acid reflux, and according to several recent studies, perhaps one of the most dangerous. About one dozen recent lawsuits filed against the company claim the drug is unreasonably dangerous and AstraZeneca failed to warn consumers of the risks, but some believe these lawsuits are just the tip of the iceberg.

In 2015 alone, Nexium made $2.49 billion in revenue for the company, which accounted for more than 10% of the company’s overall revenue for the year. But Nexium’s success comes with a high price. Earlier this year, a study published in the Journal Of The American Society Of Nephology found that patients who took drugs like Nexium had a 28% higher risk of developing chronic kidney disease, or the gradual loss of kidney function over time. The study also found patients had a 96% increased chance of developing end-stage kidney failure within five years.

In addition to damaging the kidneys, studies have linked Nexium and other heartburn drugs to osteoporosis, when bones become weak and brittle, osteopenia, when the body can’t regenerate bones as quickly, and dangerous gastrointestinal infections like Clostridium Difficile, also called C. diff. For elderly patients, drugs like Nexium can also put them at a risk for developing dementia.

These side effects can have debilitating and life-threatening consequences for patients, and the widespread use of Nexium to treat heartburn exposes millions of Americans to these risks. While only a handful of Nexium lawsuits have been filed so far, some believe the number of lawsuits could eventually reach into the thousands.

While the Nexium litigation is in the very earlier stages, it could end up costing AstraZeneca a fortune, which the company can’t afford. The company has been suffering ever since the patent on its blockbuster cholesterol drug Crestor expired this past summer. Without the revenue generated by Crestor, the company is in no position for a large payout, so how it handles these Nexium lawsuits will be crucial to its survival.