What are the biggest-selling prescription medications in the United States? Statins for heart disease? Painkillers? Antidepressants? Actually, none of the above. The biggest-selling prescription drug in the US is Nexium, a treatment for acid reflux. Surprised? You shouldn’t be. Acid reflux, or its big brother, gastroesophageal reflux disease (GERD), is the #1 disease of the digestive tract. Pretty much everyone will experience heartburn and reflux at some point in their lives. It this article we’ll share 10 nutrition and lifestyle tips for feeling better now.