Lansoprazole is a medication that belongs to a class of drugs known as proton pump inhibitors (PPIs). It works by reducing the amount of acid produced in the stomach, which helps treat conditions like gastroesophageal reflux disease (GERD) and peptic ulcers. This medication is typically taken orally, often before meals, and is available in both prescription and over-the-counter forms. Common side effects may include headache, diarrhea, and nausea, but it is generally well-tolerated. Long-term use should be monitored by a healthcare professional to avoid potential complications.