Fosrenol, whose active ingredient is lanthanum carbonate, is a medication primarily used to treat hyperphosphatemia (high phosphate levels) in patients with chronic kidney disease (CKD). It works by binding to phosphate in the digestive tract, thereby preventing its absorption into the bloodstream. This action helps to lower the levels of phosphate in the body, which is important because high phosphate levels can lead to bone and cardiovascular problems in patients with kidney disease. Fosrenol is typically administered in the form of chewable tablets, which allows for direct action within the gastrointestinal tract. As with any medication, it is important for it to be used under the guidance of a healthcare professional to ensure its safety and effectiveness.