Background
Hyperphosphatemia, or elevated blood phosphate, often develops as a result of chronically impaired renal function. The kidney is unable to excrete phosphate ions adequately, which poses a risk for the development of secondary hyperparathyroidism, renal osteodystrophy, cardiovascular calcification, and cardiovascular disease. Treatment options include dialysis, diet, and the use of phosphate binders.
Effects
Phosphate binders exert their effects locally in the stomach or intestine. They bind phosphate ions and direct them to excretion in the stool. The majority are the salts of di- or trivalent metal ions, which form a new salt with the phosphate that is poorly soluble in water. Depending on the active ingredient, the aluminum, calcium, lanthanum or magnesium phosphates formed cannot be absorbed and are thus eliminated. Sevelamer is a polymer with amino groups that binds the phosphate ions.
Active ingredients
- Aluminum chloride hydroxide (phosphonorm).
- Calcium acetate (various) Detailed information.
- Calcium carbonate (calcium carbonate Salmon Pharma, calcium phosphate binder Bichsel).
- Lanthanum carbonate (Fosrenol)
- Magnesium carbonate (not commercially available in many countries).
- Sevelamer chloride (Renagel)
- Sevelamer carbonate (Renvela)
Indications and dosage
Phosphate binders are used to treat or prevent hyperphosphatemia in patients with chronic renal failure. The drugs must be taken with meals.
Contraindications
Phosphate binders are contraindicated in hypersensitivity and hypophosphatemia. Other contraindications depend on the substance.
Interactions
Drug interactions, if any, should be specifically noted during treatment. Phosphate binders, first, have the potential to bind and inactivate numerous other drugs. These are not absorbed and their bioavailability and pharmacologic effects are reduced. An interval of at least two hours between the intake of phosphate binders and sensitive drugs is recommended. Second, phosphate binders can have an effect on gastric pH. Like antacids, they neutralize stomach acid, thereby increasing pH.
Adverse effects
Adverse effects are substance-dependent. Phosphate binders containing aluminum are controversial and are no longer recommended in the literature because they can lead to aluminum deposition in bone, osteomalacia, dementia, and anemia due to aluminum intoxication. When taking the calcium salts, hypercalcemia can occur due to increased calcium intake. The risk is increased with concomitant administration of vitamin D. Appropriate precautions must be observed. Magnesium salts can cause hypermagnesemia and diarrhea and have a lower binding capacity. They are no longer commercially available in many countries. Less severe side effects are in principle to be expected under sevelamer and lanthanum carbonate, as they are aluminum and calcium free. However, sevelamer often causes gastrointestinal discomfort, and lanthanum carbonate can potentially accumulate during long-term therapy.
