On the growing list of things that could possibly give you a heart attack, you can now add antacids. According to a new study published in PLOS ONE, researchers at Houston Methodist and Stanford University found that certain types of antacids using proton pump inhibitors increase your likelihood of suffering a heart attack, regardless of whether you’ve had preexisting heart conditions.

For the study, researchers analyzed 16 million clinical documents representing 2.9 million patients. There results showed that patients who were prescribed common antacids with proton pump inhibitors were 16 to 21 percent more likely to experience a heart attack. Interestingly enough, patients who were prescribed antacids with H2 blocker, the second most common component in many frequently used antacids, had no increased likelihood of heart attack. The research was conducted following a 2013 Circulation report that showed, on a molecular level, how PPIs could potentially lead to long-term cardiovascular disease.

“Our earlier work identified that the PPIs can adversely affect the endothelium, the Teflon-like lining of the blood vessels,” said Dr. John Cookie, senior author of the study, in a recent press release. “That observation led us to hypothesize that anyone taking PPIs may be at greater risk for heart attack. Accordingly, in two large populations of patients, we asked what happened to people that were on PPIs versus other medications for the stomach.”

In their most recent study, researchers were able to solidify the connection, finding proof that PPIs do contribute to heart attacks. Researchers used two different databases to gather their information, including the STRIDE (Stanford Translational Research Integrated Database Environment) which possesses information on 1.8 million patients of Stanford hospitals and clinics, along with electronic medical records from Practice Fusion Inc., featuring information on 1.1 million patients.

Focusing on patients given PPIs or H2 blockers, researchers looked to see if participants had any recorded experiences of heart attacks while on either of these drugs. This is where researchers drew their 16 to 21 percent statistic, which is given as a range because of the uncertainty in the estimation process. They also found PPI using patients’ risk of having a heart attack went up 1.16-1.21 fold. Once again, those on H2 blockers were found to be unaffected.

“By looking at the data from people who were given PPI drugs primarily for acid reflux and had no prior history of heart disease, our data-mining pipeline signals an association with a higher rate of heart attacks,” said Dr. Nigma H. Shah of Stanford. “Our results demonstrate that PPIs appear to be associated with elevated risk of heart attack in the general population while H2 blockers show no such association.”

The results of this study are alarming, considering the frequency with which the drug is used; according the FDA, 1 in 14 Americans have taken proton pump inhibitors. The FDA also states that in 2009, PPIs represented a $13 billion a year global sales market, as well as the third-most taken drug in the United States. PPIs are most often prescribed for digestive system issues, including gastro-esophageal reflux disease (GERD), infections that often cause ulcers, Zollinger-Ellison syndrome and Barrett’s esophagus. Drugs containing PPIs are available over-the-counter, and are distinguished by a listed chemical ending in the suffix “-prazole”, usually omeprazole or lansoprazole. The most common antacids with PPIs on the market are Nexium, Prilosec, and PrevAcid.

Antacids containing H2 blockers, which have no established effect, usually consist of chemicals like cimetidine and ranitidine. Examples include Zantac and Tagamet.

In more recent years, the safety of PPIs has been under investigation. It was previously thought that PPIs were only risky for a very specific, few patients who had coronary artery disease and were prescribed the anti-platelet drug clopidogrel. “Investigators originally assumed this was due to a drug-drug interaction between these compounds, and the FDA went so far as to release a warning about their concomitant use,” said Dr. Nicholas Leeper, Stanford vascular medicine specialist.

However, the 2013 Circulation report suggested the risk was more widespread, potentially threatening the general population. “This led us to use powerful ‘big-data’ approaches to try to determine whether PPIs might in fact be associated with risk in ‘all comers’,” said Leeper. “Our report raises concerns that these drugs -- which are available over the counter and are among the most commonly prescribed drugs in the world -- may not be as safe as we previously assumed.”

Researchers are hoping they will soon be able to conduct a larger, randomized trial where they can test if PPIs are harmful to an even wider demographic of patients.

Source: Shah N, Leeper N, Iyer S, et al. Proton Pump Inhibitor Usage and the Risk of Myocardial Infarction in the General Population. PLOS ONE. 2015.