Oral phosphate binders are medications taken with meals and snacks to help the body get rid of extra phosphate from food. These are not absorbed into the bloodstream like typical medicines. Instead, they travel through the digestive system, where their primary job is to reduce the amount of phosphate absorbed from the diet.
The Role of Phosphate in the Body
Phosphorus, which becomes phosphate in the body, is a mineral that plays a part in many biological processes. It is a fundamental building block for bones and teeth, working alongside calcium to create their strong structure.
When kidneys are not functioning at full capacity, they can lose the ability to effectively remove this surplus phosphate. This leads to a condition called hyperphosphatemia, where phosphate levels in the blood become too high. Over time, this imbalance can pull calcium out of the bones, making them weak and more susceptible to fractures.
The consequences of high phosphate levels extend beyond bone health. The excess phosphate and calcium can form hard, mineral deposits in parts of the body where they don’t belong. These deposits can accumulate in the walls of blood vessels, a process known as vascular calcification, making them stiff and narrow. This condition can increase the risk of serious cardiovascular problems, including heart attacks and strokes.
How Phosphate Binders Work
Phosphate binders function within the gastrointestinal tract to limit the absorption of phosphate from food. They are not absorbed by the body to act on phosphate already in the bloodstream. For this reason, it is important that they are taken with food.
Think of these binders as a type of magnet for dietary phosphate. As the food is digested, the binder latches onto the phosphate molecules present in the stomach and intestines. This action forms a new, larger compound that the body cannot absorb through the gut wall.
This newly formed, bound phosphate then continues its journey through the digestive system. Because it cannot be absorbed, it is ultimately eliminated from the body in the stool. This process effectively reduces the total amount of phosphate that can enter the bloodstream from a given meal, helping to lower the overall phosphate levels in the body.
Types of Phosphate Binders
Phosphate binders are categorized into two main groups: those that contain calcium and those that do not. The selection of a specific binder depends on an individual’s particular health needs and blood chemistry.
Calcium-based binders, such as calcium carbonate and calcium acetate, are often used. They are effective at binding to phosphate, forming insoluble calcium-phosphate complexes that are then excreted. While effective, a consideration with these binders is that they can sometimes lead to elevated calcium levels in the blood, a condition known as hypercalcemia.
Non-calcium-based binders include several different agents. Sevelamer, for example, is a polymer that binds to phosphate through ionic and hydrogen bonds. Lanthanum carbonate is another option that uses the element lanthanum to form insoluble complexes with dietary phosphate. More recently, iron-based binders, such as sucroferric oxyhydroxide and ferric citrate, have become available; these use ferric iron to bind phosphate in the GI tract.
Common Side Effects and Management
It is common for individuals to experience issues such as constipation, nausea, gas, or general stomach upset. The specific side effects can vary depending on the type of binder being used. For example, sevelamer may cause nausea or changes in bowel habits.
Managing these gastrointestinal side effects often involves practical dietary and lifestyle adjustments. To address constipation, a healthcare provider might recommend gradually increasing fiber intake, with guidance from a dietitian to ensure it aligns with any other dietary restrictions. Staying well-hydrated by drinking enough water can also help soften stool.
For persistent side effects, it is important to have an open conversation with a doctor or pharmacist. They may suggest adjusting the dose or timing of the medication. In some cases, they might recommend a stool softener for constipation or suggest trying a different type of phosphate binder that may be better tolerated.