Calcium Acetate vs Calcium Carbonate: Role as Phosphate Binders in Hemodialysis Patients

What is Hemodialysis?

Before learning about the role of?phosphate binders?in Hemodialysis patients, let us know briefly about Hemodialysis.

Hemodialysis is a procedure in which the blood of the patient is purified with the help of a filter called a dialyzer or artificial kidney. The waste from blood is filtered out and clean blood is restored in the body. Not only does it control the blood pressure but also maintains the electrolyte balance in the body. For?CKD?(Chronic Kidney Disease) patient’s diet becomes one of the most important factors that influence the health of a patient.

Why Phosphate is increased/toxic in hemodialysis patients??

Phosphate is one of the important anion present in bones and soft tissues of our body which is regulated by bone absorption and renal excretion. Healthy kidneys can easily filter excess phosphorus out of our systems. In CKD patients, where glomerular filtration rate is reduced, phosphate is not filtered out completely, thus, causing hyperphosphatemia in the body.?

Do you know how an excess amount of Phosphorus is harmful our body??

Excess phosphorus stimulates the secretion of parathyroid hormone which in turn removes calcium from bones into the bloodstream to maintain the homeostatic balance of serum calcium, thus, weakening the bone. Above that, a high level of phosphorus and calcium in the blood can lead to calcification or deposits in vessels, lungs, or the heart. Dialysis does remove but small amounts of phosphorus from the blood.?

The high amount of?phosphorus?in the blood is known as Hyperphosphatemia, a condition that is inevitable in End-Stage Kidney Disease. The renal diet and dialysis alone are not sufficient to effectively maintain the homeostatic balance of phosphate in the blood. This is where Phosphorus binders come into play. They prevent the absorption of phosphorus from food and help in eliminating it from the body via stools.?

The Action of Phosphate Binders:?

?Phosphate binders work effectively by binding to phosphate in the gastrointestinal tract. Binder is an active cation (carbonate, acetate, citrate) that exchanges with anion phosphate to form a compound that is nonabsorbable and is excreted in the feces. These drugs are usually taken with the meals so that phosphate in the food binds with the agent and is taken along the digestive tract to eliminate it. Some binders soak the phosphate directly, and some act as magnets.

Types of Phosphate Binders

Various types of Phosphate binders are:

a.) Aluminium Phosphate Binder: Though they are cheap and efficient their proven toxicity sets drawbacks to aluminum binders. CKD patients can absorb the toxic amount of aluminum when aluminum binders are ingested.

b.) Sevelamer binders: Aluminium and Calcium free efficient binders with no absorption in gastrointestinal but are costly and have a high pill load.

c)?Calcium Acetate?Binders: Effective binder in Renal Patients

d)?Calcium carbonate?Binders: Cost-effective but less efficient than?Calcium Acetate

Calcium Acetate and Calcium carbonate:- Phosphorus binding power and Hypercalcemic effect and Tolerance

Calcium salts have replaced aluminum binders as they are effective and safe alternatives. You are now clear why phosphate levels are increased in hemodialysis patients and how it could be life-threatening. So, now let us compare?Calcium Acetate?and Calcium Carbonate as Phosphate binders on basis of their Phosphorus binding power, Hypercalcemic effect, and Tolerance.

Calcium Carbonate

• Principle Salt effectively replaced Aluminium binders.
• A large dose of Calcium carbonate was needed to achieve the desired quantity to bind with phosphate to eliminate it. In doing so, a large amount of calcium is used to get absorbed resulting in hypercalcemia and calcium deposits in various organs.
• Phosphorus binding/ Calcium Absorption ratio was three times less than calcium acetate.
• Calcium carbonate is soluble in acidic pH only and not at higher pH. It binds slowly and incompletely with Phosphate as compared to acetate.

Calcium Acetate

• Calcium Acetate is the effective Phosphate binder in Renal Patients
• Calcium Acetate after binding with phosphate release bicarbonate which is rapidly metabolized to HCO1 preventing any harmful metabolic consequence.?
• Calcium Acetate is considered to be a choice for hyperphosphatemia in Hemodialysis patients.
• Calcium acetate controls serum phosphorus and calcium-phosphate product more effectively than sevelamer hydrochloride.
• Low doses of Calcium acetate with higher phosphorus binding and calcium absorption ratio, are less likely to absorb calcium. Thus, hypercalcemia and deposition of calcium are less likely to occur with calcium acetate.
• On basis of the Phosphorus binding/ Calcium Binding ratio, Calcium acetate is three times more efficient than calcium carbonate.
• Calcium Acetate is readily soluble and binds with Phosphorus in both alkaline and acidic pH. In a condition like Achlorhydria which can be seen in Renal disease patients, Calcium acetate is the choice of treatment along with antacid preparation and gastric secretion.

Calcium AcetateCalcium CarbonateHypercalcemic EffectLess likelyDefiniteDose RequiredlesshighPhosphate BindingThree times morelessSolubilityReadily soluble in alkaline and acidic pHSoluble in acidic pH only