Researchers recently revealed that some over-the-counter antacids used for treating heartburn, like Prilosec are associated with 20% higher risk of heart attack.

The study conducted by researchers at Stanford University was published in journal PLOS ONE. It was specifically based on a large data-mining study of nearly three million health records.

According to the study, adult users of proton pump inhibitor medications (PPIs) have a 16-21% higher likelihood of experiencing a heart attack than people who don't use the common antacid drugs.

Researchers during the study looked at drugs like Prilosec, Nexium and Prevacid, which are part of a class of drugs known as proton-pump inhibitors (PPIs).

These are among the world's most widely prescribed drugs, and helps in generating almost $14 billion in annual sales.

The study showed that about 20 million Americans, or one in every 14 US resident, uses PPIs such as Prilosec (omeprazole) for heartburn, acid reflux or gastroesophageal reflux disease.

So far these antacids were considered to be safe unless they were taken with blood thinner Plavix (clopidogrel).

Although the study was unsuccessful in proving that antacids can cause heart attacks, researchers believe that the problem might involve how the drugs affect the lining of blood vessels.

Researchers stated that another kind of antacid known as H2 blockers, showed no higher risk of heart attack. These drugs include Zantac and Tagamet.

Senior author John Cooke, MD, Ph. D, said, "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 stomach".