Phosphate binder

Phosphate binders are medications used to reduce the absorption of dietary phosphate; they are taken along with meals and snacks. They are frequently used in people with chronic kidney failure (CKF), who are less able to excrete phosphate, resulting in an elevated serum phosphate.

Mechanism of action

These agents work by binding to phosphate in the GI tract, thereby making it unavailable to the body for absorption. Hence, these drugs are usually taken with meals to bind any phosphate that may be present in the ingested food. Phosphate binders may be simple molecular entities (such as magnesium, aluminium, calcium, or lanthanum salts) that react with phosphate and form an insoluble compound. Phosphate binders such as sevelamer may also be polymeric structures which bind to phosphate and are then excreted.

Medical use

For people with chronic kidney failure, controlling serum phosphate is important because it is associated with bone pathology and regulated together with serum calcium by the parathyroid hormone (PTH).

They are also used in hypoparathyroidism which presents with hypocalcemia with hyperphosphatemia.

Adverse effects

With regard to phosphate binders, aluminium-containing compounds (such as aluminium hydroxide) are the least preferred because prolonged aluminium intake can cause encephalopathy and osteomalacia. If calcium is already being used as a supplement, additional calcium used as a phosphate binder may cause hypercalcemia and tissue-damaging calcinosis. One may avoid these adverse effects by using phosphate binders that do not contain calcium or aluminium as active ingredients, such as lanthanum carbonate or sevelamer.

Choice of agent

There have been limited trials comparing phosphate binders to placebo in the treatment of hyperphosphatemia in people with chronic kidney disease. When compared with people receiving calcium-based binders, people taking sevelamer have a reduced all-cause mortality.[1]

Types
Summary of Common Oral Phosphate Binders[2]
Phosphate BinderBrandsAdvantagesDisadvantages
Aluminum saltsAlucapsCalcium freeRisk of aluminum toxicity
BasaljelHigh binder efficiency regardless of pHRequires frequent monitoring-extra cost
Cheap
Moderate tablet burden
Calcium carbonateCalcichewAluminum freeCalcium containing-potential risk of hypercalcemia and ectopic calcification
TitralacModerate binding efficacyParathyroid hormone oversuppression
Relatively low costGastrointestinal side effects
Moderate tablet burdenEfficacy pH dependent
Chewable
Calcium acetateLenal AceAluminum freeCalcium containing-potential risk of hypercalcemia and ectopic calcification
PhosLoHigher efficacy than calcichew/sevelamerParathyroid hormone oversuppression
Moderately cheapGastrointestinal side effects
Lower calcium load than calcium carbonateLarge tablets & capsules, nonchewable formulation
Sevelamer hydrochloride/Sevelamer carbonateRenagelAluminium and calcium freeRelatively costly
RenvelaNo gastrointestinal absorptionHigh pill burden
Moderate efficacyLarge tablets, nonchewable formulation
Reduces total and low-density lipoprotein cholesterolGastrointestinal side effects
Binds fat-soluble vitamins
Lanthanum carbonateFosrenolAluminum and calcium freeRelatively costly
Minimal gastrointestinal absorptionGastrointestinal side effects
High efficacy across full pH rangeLarger tablet size may cause choking if not chewed well
Chewable formulation
Palatable
Low tablet burden
Ferric Citrate Auryxia Iron based Very costly
Tablets can be toxic to young children
Stool discoloration - may turn them black, obscuring intestinal bleeding

References
  1. Patel, L; Bernard, LM; Elder, GJ (14 December 2015). "Sevelamer versus calcium-based binders for treatment of hyperphosphatemia in CKD: a meta-analysis of randomized controlled trials". Clinical Journal of the American Society of Nephrology. 11 (2): 232–244. doi:10.2215/CJN.06800615. PMC 4741042. PMID 26668024.
  2. Burtis, C.A.; Ashwood, E.R. and Bruns, D.E. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 5th Edition. Elsevier. pp1552
  1. ^ Lederer E, Ouseph R, Erbeck K. Hyperphosphatemia, eMedicine.com, URL: Hyperphosphatemia: Practice Essentials, Background, Pathophysiology, Accessed on July 14, 2005.
  2. ^ Spiegel, David M.; Farmer, Beverly; Smits, Gerard; Chonchol, Michel (2007). "Magnesium Carbonate is an Effective Phosphate Binder for Chronic Hemodialysis Patients: A Pilot Study". Journal of Renal Nutrition. 17 (6): 416–22. doi:10.1053/j.jrn.2007.08.005. PMID 17971314.

Common Phosphate Binders
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