New Treatments for High Blood Phosphate Levels

• High serum phosphate levels are commonly noted in patients with kidney failure.
• Calcium-based medications are commonly used, but can cause hypercalcemia (high calcium level in the blood). Aluminum and magnesium-based phosphate binders are no longer preferred.
• Sevelamer and lanthanum are relatively newer drugs in the treatment of hyperphosphatemia.
• The latest drugs approved for the condition are the iron-based sucroferric oxyhydroxide and ferric citrate.

With the approval of iron-based phosphate binders, the choice of drugs for the treatment of hyperphosphatemia has increased. A recent article in the US Pharmacist reviewed the available treatments for high serum phosphate levels, which are listed below. Phosphate is an ion that helps maintain bone health along with calcium. Its level in the blood is maintained at 2.7 to 4.5 mg/dL. High serum phosphate levels or hyperphosphatemia are often noted in patients with chronic kidney disease (CKD) among other conditions. Hyperphosphatemia increases the chances of heart disease and therefore, the level of phosphate should be brought down to normal with treatment. This is achieved through dialysis in kidney failure patients, along with dietary phosphate restriction and the use of certain medications called phosphate binding agents.

Phosphate binding agents bind to phosphates in the digestive tract and thereby reduce their absorption into the body. The older phosphate binders, aluminum hydroxide and magnesium hydroxide, commonly used as antacids, are no longer preferred due to their side effects.

Calcium carbonate, on the other hand, has been popular due to its effectiveness as well as its low cost. It can increase blood calcium levels, which should be watched for during treatment. Calcium acetate is also used, but it has side effects like nausea and vomiting, can prevent absorption of other medications from the digestive tract, and can cause high calcium levels though to a lesser extent.

Phosphate binders that followed the above were sevelamer and lanthanum carbonate. Sevelamer is used as two salts: hydrochloride and carbonate. When taken orally, it remains in the digestive tract and prevents absorption of phosphates into the blood. However, it can also prevent the absorption of several other medications given to the patient. The exact mechanism of action of lanthanum carbonate is not known.

The most recent phosphate binders in the market are sucroferric oxyhydroxide and ferric citrate, which hopefully will be devoid of the side effects of the older treatments. These contain iron, therefore besides their therapeutic effect in hyperphosphatemia, they may be able to address the problem of low iron content or anemia in patients with kidney disease and at the same time, avoid hypercalcemia, which is common with calcium-based treatments.

Sucroferric oxyhydroxide binds to phosphate in the digestive tract and prevents its absorption. It is approved for patients with chronic kidney disease on dialysis. However, it does release sugar, which is absorbed and can increase the blood glucose level in patients with diabetes. The iron may also cause adverse effects like altered taste, diarrhea and black stools.

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Ferric citrate is another iron containing phosphate binder that is latest in the armamentarium of hyperphosphatemia. Iron-related side effects can occur. The iron-containing drugs should not be used in those at a risk of iron overload.

Thus, it can be noted that even the newer drugs do have side effects. However, since the choice has increased, the appropriate drug can be chosen depending on the underlying characteristics of the particular patient.

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References:

1. Stormont R, McCoy R, Bashir K, Malesker MA. New Pharmacotherapy Options for Hyperphosphatemia. US Pharm. 2015;41(3):HS18-HS.

Source-Medindia