Nexium is a proton pump inhibitor used to treat acid reflux and stomach ulcers. It works by reducing acid production in the stomach. Nexium is typically taken once daily before meals, with the dosage and duration determined by the condition being treated. Common side effects include headache and diarrhea, and it's important to avoid interactions with other medications. The goals of Nexium therapy are to relieve acid reflux symptoms and heal esophageal erosions.