The treatment of uraemic hyperphosphataemia with calcium acetate and calcium carbonate: a comparative study

Recommended calcium intake in adults and children with chronic kidney disease-a European consensus statement

Mineral and bone disorders (MBD) are common in patients with chronic kidney disease (CKD), contributing to significant morbidity and mortality. For several decades, the first-line approach to controlling hyperparathyroidism in CKD was by exogenous calcium loading. Since the turn of the millennium, however, a growing awareness of vascular calcification risk has led to a paradigm shift in management and a move away from calcium-based phosphate binders. As a consequence, contemporary CKD patients may be at risk of a negative calcium balance, which, in turn, may compromise bone health, contributing to renal bone disease and increased fracture risk. A calcium intake below a certain threshold may be as problematic as a high intake, worsening the MBD syndrome of CKD, but is not addressed in current clinical practice guidelines. The CKD-MBD and European Renal Nutrition working groups of the European Renal Association (ERA), together with the CKD-MBD and Dialysis working groups of the European Society for Pediatric Nephrology (ESPN), developed key evidence points and clinical practice points on calcium management in children and adults with CKD across stages of disease. These were reviewed by a Delphi panel consisting of ERA and ESPN working groups members. The main clinical practice points include a suggested total calcium intake from diet and medications of 800-1000 mg/day and not exceeding 1500 mg/day to maintain a neutral calcium balance in adults with CKD. In children with CKD, total calcium intake should be kept within the age-appropriate normal range. These statements provide information and may assist in decision-making, but in the absence of high-level evidence must be carefully considered and adapted to individual patient needs.

Phosphate binders for preventing and treating chronic kidney disease-mineral and bone disorder (CKD-MBD)

BACKGROUND

Phosphate binders are used to reduce positive phosphate balance and to lower serum phosphate levels for people with chronic kidney disease (CKD) with the aim to prevent progression of chronic kidney disease-mineral and bone disorder (CKD-MBD). This is an update of a review first published in 2011.

OBJECTIVES

The aim of this review was to assess the benefits and harms of phosphate binders for people with CKD with particular reference to relevant biochemical end-points, musculoskeletal and cardiovascular morbidity, hospitalisation, and death.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 12 July 2018 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) or quasi-RCTs of adults with CKD of any GFR category comparing a phosphate binder to another phosphate binder, placebo or usual care to lower serum phosphate. Outcomes included all-cause and cardiovascular death, myocardial infarction, stroke, adverse events, vascular calcification and bone fracture, and surrogates for such outcomes including serum phosphate, parathyroid hormone (PTH), and FGF23.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies for inclusion and extracted study data. We applied the Cochrane 'Risk of Bias' tool and used the GRADE process to assess evidence certainty. We estimated treatment effects using random-effects meta-analysis. Results were expressed as risk ratios (RR) for dichotomous outcomes together with 95% confidence intervals (CI) or mean differences (MD) or standardised MD (SMD) for continuous outcomes.

MAIN RESULTS

We included 104 studies involving 13,744 adults. Sixty-nine new studies were added to this 2018 update.Most placebo or usual care controlled studies were among participants with CKD G2 to G5 not requiring dialysis (15/25 studies involving 1467 participants) while most head to head studies involved participants with CKD G5D treated with dialysis (74/81 studies involving 10,364 participants). Overall, seven studies compared sevelamer with placebo or usual care (667 participants), seven compared lanthanum to placebo or usual care (515 participants), three compared iron to placebo or usual care (422 participants), and four compared calcium to placebo or usual care (278 participants). Thirty studies compared sevelamer to calcium (5424 participants), and fourteen studies compared lanthanum to calcium (1690 participants). No study compared iron-based binders to calcium. The remaining studies evaluated comparisons between sevelamer (hydrochloride or carbonate), sevelamer plus calcium, lanthanum, iron (ferric citrate, sucroferric oxyhydroxide, stabilised polynuclear iron(III)-oxyhydroxide), calcium (acetate, ketoglutarate, carbonate), bixalomer, colestilan, magnesium (carbonate), magnesium plus calcium, aluminium hydroxide, sucralfate, the inhibitor of phosphate absorption nicotinamide, placebo, or usual care without binder. In 82 studies, treatment was evaluated among adults with CKD G5D treated with haemodialysis or peritoneal dialysis, while in 22 studies, treatment was evaluated among participants with CKD G2 to G5. The duration of study follow-up ranged from 8 weeks to 36 months (median 3.7 months). The sample size ranged from 8 to 2103 participants (median 69). The mean age ranged between 42.6 and 68.9 years.Random sequence generation and allocation concealment were low risk in 25 and 15 studies, respectively. Twenty-seven studies reported low risk methods for blinding of participants, investigators, and outcome assessors. Thirty-one studies were at low risk of attrition bias and 69 studies were at low risk of selective reporting bias.In CKD G2 to G5, compared with placebo or usual care, sevelamer, lanthanum, iron and calcium-based phosphate binders had uncertain or inestimable effects on death (all causes), cardiovascular death, myocardial infarction, stroke, fracture, or coronary artery calcification. Sevelamer may lead to constipation (RR 6.92, CI 2.24 to 21.4; low certainty) and lanthanum (RR 2.98, CI 1.21 to 7.30, moderate certainty) and iron-based binders (RR 2.66, CI 1.15 to 6.12, moderate certainty) probably increased constipation compared with placebo or usual care. Lanthanum may result in vomiting (RR 3.72, CI 1.36 to 10.18, low certainty). Iron-based binders probably result in diarrhoea (RR 2.81, CI 1.18 to 6.68, high certainty), while the risks of other adverse events for all binders were uncertain.In CKD G5D sevelamer may lead to lower death (all causes) (RR 0.53, CI 0.30 to 0.91, low certainty) and induce less hypercalcaemia (RR 0.30, CI 0.20 to 0.43, low certainty) when compared with calcium-based binders, and has uncertain or inestimable effects on cardiovascular death, myocardial infarction, stroke, fracture, or coronary artery calcification. The finding of lower death with sevelamer compared with calcium was present when the analysis was restricted to studies at low risk of bias (RR 0.50, CI 0.32 to 0.77). In absolute terms, sevelamer may lower risk of death (all causes) from 210 per 1000 to 105 per 1000 over a follow-up of up to 36 months, compared to calcium-based binders. Compared with calcium-based binders, lanthanum had uncertain effects with respect to all-cause or cardiovascular death, myocardial infarction, stroke, fracture, or coronary artery calcification and probably had reduced risks of treatment-related hypercalcaemia (RR 0.16, CI 0.06 to 0.43, low certainty). There were no head-to-head studies of iron-based binders compared with calcium. The paucity of placebo-controlled studies in CKD G5D has led to uncertainty about the effects of phosphate binders on patient-important outcomes compared with placebo.It is uncertain whether the effects of binders on clinically-relevant outcomes were different for patients who were and were not treated with dialysis in subgroup analyses.

AUTHORS' CONCLUSIONS

In studies of adults with CKD G5D treated with dialysis, sevelamer may lower death (all causes) compared to calcium-based binders and incur less treatment-related hypercalcaemia, while we found no clinically important benefits of any phosphate binder on cardiovascular death, myocardial infarction, stroke, fracture or coronary artery calcification. The effects of binders on patient-important outcomes compared to placebo are uncertain. In patients with CKD G2 to G5, the effects of sevelamer, lanthanum, and iron-based phosphate binders on cardiovascular, vascular calcification, and bone outcomes compared to placebo or usual care, are also uncertain and they may incur constipation, while iron-based binders may lead to diarrhoea.

Hyperphosphatemia in Dialysis Patients: The Therapeutic Role of Lanthanum Carbonate

Phosphate overload is a dramatic consequence in end-stage renal disease (ESRD) patients. Recent studies have well documented that abnormalities in mineral and bone metabolism in these patients are associated with increased cardiovascular morbidity and mortality. Elevated serum phosphate and calcium-phosphate product levels play an important role in the pathogenesis of secondary hyperparathyroidism and extra-skeletal calcification in dialysis patients. Furthermore, inorganic phosphate may cause vascular calcification directly through a real “ossification” of the tunica media in the vasculature of ESRD patients.

The “classical” treatment of secondary hyperparathyroidism and hyperphosphatemia in ESRD patients consists of either calcium- or aluminum-based phosphate binders and calcitriol administration. Unfortunately, this “old generation” therapy is not free of complications. This review paper suggests that new calcium- and aluminum-free phosphate binders, such as lanthanum carbonate, can be used to treat hyperphosphatemia and secondary hyperparathyroidism in ESRD patients.

Phosphate management in chronic kidney disease

PURPOSE OF REVIEW

The review focuses on the rationale and evidence behind management strategies for hyperphosphatemia in patients with chronic kidney disease (CKD).

RECENT FINDINGS

Optimal management of phosphate in CKD remains an area of uncertainty, but multiple studies now point to a clinical benefit from the use of phosphate binders. Evidence of improved survival is particularly strong with sevelamer, though it remains unclear whether the absence of calcium or other properties of sevelamer are responsible for this relationship. Newer agents, such as iron-based binders or niacin compounds to inhibit phosphorus absorption, may have additional benefits which will be better defined with additional experience. A reduced pill count may be a particularly beneficial characteristic of newer agents, and has been associated with improved response to therapy. Increased use of frequent, nocturnal hemodialysis is an additional tool to help ameliorate phosphate control. Data on the reduction of fibroblast growth factor 23 through use of phosphate binders remain weak.

SUMMARY

An improved understanding of phosphate regulation and the development of new therapeutic agents have reinvigorated a once stagnant field, but significant changes to practice cannot yet be justified. There is increasing support for using sevelamer in place of calcium-based binders, though economic practicability remains challenging.

Derangements in phosphate metabolism in chronic kidney diseases/endstage renal disease: therapeutic considerations

The changes in phosphate (PO(4)) metabolism across the spectrum of chronic kidney disease (CKD) and specific strategies to address these abnormalities by reducing PO(4) loads are discussed in this review. This review also addresses briefly the evidence for specific PO(4) serum targets in CKD and endstage renal disease (ESRD) and the potential for other biomarkers such as fibroblast growth factor-23 (FGF-23) to define disease and monitor the effectiveness of therapy. As renal function declines, single nephron excretion of PO(4) must increase to maintain PO(4) balance. Abnormalities in PO(4) metabolism occur early in CKD. Compensatory changes in renal PO(4) handling are sufficient to maintain a normal serum PO(4) level in early stages of CKD, but in more advanced CKD, these processes no longer suffice and overt hyperphosphatemia develops. The resulting increased PO(4) burden contributes directly to development of secondary hyperparathyroidism. The FGF-23 increases early in CKD, likely in response to abnormal PO(4) metabolism, and mediates processes that help restore serum PO(4) levels to normal in CKD stage 3 and in early stage 4. The increased PO(4) burden and subsequent overt hyperphosphatemia are associated with increased mortality and morbidity. Dietary PO(4) restriction, modification of dialysis prescriptions, and administration of oral PO(4) binders can restore PO(4) balance. As CKD progresses, population-based studies demonstrate that diet alone is typically not able to prevent or treat hyperphosphatemia. Dialysis modalities that are currently used often fail to remove sufficient PO(4) to prevent hyperphosphatemia in patients with an inadequately controlled dietary PO(4) load. This is particularly likely among patients without significant residual renal function. Thus, in the majority of ESRD patients, PO(4) binders remain the mainstay of therapy for hyperphosphatemia. All currently available PO(4) binders can restore serum PO(4) to the required level when administered appropriately and in conjunction with dietary PO(4) restrictions. PO(4) binders differ regarding their potential side-effects and impact on long-term patient-centered outcomes. Which of the PO(4) binders might result in the most favorable survival and cardiovascular morbidity profiles and which remain uncertain, remains a subject of considerable clinical investigation. Compelling observational and more limited randomized controlled trial (RCT) evidence support the view that PO(4) binders might differ in their effects on mortality and/or morbidity. The limited evidence from RCTs is mostly congruent with the findings from large observational studies. In particular, evidences from both epidemiologic and RCT support the view that excess calcium administration may independently increase the risk of cardiovascular disease in individuals with normal renal function and in patients with CKD and ESRD. Additional RCT evidence might help determine the degree at which any increased risk from oral calcium exposure can be mitigated with the use of noncalcium-based PO(4) binders. Judicious control of PO(4) early in CKD, possibly monitored by measures of FGF-23, could potentially reduce the risk of development of renal secondary hyperparathyroidism and all of the adverse clinical consequences of poorly controlled CKD-mineral and bone disorder. The mainstays of therapy are likely to include a balance of dietary restriction and PO(4) binders to reduce PO(4) input, and in ESRD patients, dialysis modalities to augment PO(4) output.

Phosphate binders for preventing and treating bone disease in chronic kidney disease patients

BACKGROUND

Phosphate binders are widely used to lower serum phosphorus levels in people with chronic kidney disease (CKD) but their impact in CKD remains controversial.

OBJECTIVES

To review the effects of various phosphate binders on biochemical and patient-level end-points in CKD stages 3 to 5D.

SEARCH STRATEGY

In March 2010 we searched MEDLINE, EMBASE, the Cochrane Renal Group's Specialised Register and CENTRAL for relevant studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs that assessed the effects of various phosphate binders in adults with CKD.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed search results and extracted data. Results were expressed as mean differences (MD) for continuous outcomes and risk ratios (RR) for dichotomous outcomes with 95% confidence intervals (CI) using a random-effects model.

MAIN RESULTS

Sixty studies (7631 participants) were included. There was no significant reduction in all-cause mortality (10 studies, 3079 participants: RR 0.73, 95% CI 0.46 to 1.16), or serum calcium by phosphorus (Ca x P) product with sevelamer hydrochloride compared to calcium-based agents. There was a significant reduction in serum phosphorus (16 studies, 3126 participants: MD 0.23 mg/dL, 95% CI 0.04 to 0.42) and parathyroid hormone (PTH) (12 studies, 2551 participants; MD 56 pg/mL, 95% CI 26 to 84) but a significant increase in the risk of hypercalcaemia (12 studies, 1144 participants: RR 0.45, 95% CI 0.35 to 0.59) with calcium-based agents compared to sevelamer hydrochloride. There was a significant increase in the risk of adverse gastrointestinal events with sevelamer hydrochloride in comparison to calcium salts (5 studies, 498 participants: RR 1.58, 95% CI 1.11 to 2.25). Compared with calcium-based agents, lanthanum significantly reduced serum calcium (2 studies, 122 participants: MD -0.30 mg/dL, 95% CI -0.64 to -0.25) and the Ca x P product, but not serum phosphorus levels. The effects of calcium acetate on biochemical end-points were similar to those of calcium carbonate. The phosphorus lowering effects of novel agents such as ferric citrate, colestilan and niacinamide were only reported in a few studies.

AUTHORS' CONCLUSIONS

Available phosphate-binding agents have been shown to reduce phosphorus levels in comparison to placebo. However, there are insufficient data to establish the comparative superiority of novel non-calcium binding agents over calcium-containing phosphate binders for patient-level outcomes such as all-cause mortality and cardiovascular end-points in CKD.

Evaluation of calcium acetate/magnesium carbonate as a phosphate binder compared with sevelamer hydrochloride in haemodialysis patients: a controlled randomized study (CALMAG study) assessing efficacy and tolerability

BACKGROUND

Phosphate binders are required to control serum phosphorus in dialysis patients. A phosphate binder combining calcium and magnesium offers an interesting therapeutic option.

METHODS

This controlled randomized, investigator-masked, multicentre trial investigated the effect of calcium acetate/magnesium carbonate (CaMg) on serum phosphorus levels compared with sevelamer hydrochloride (HCl). The study aim was to show non-inferiority of CaMg in lowering serum phosphorus levels into Kidney Disease Outcome Quality Initiative (K/DOQI) target level range after 24 weeks. Three hundred and twenty-six patients from five European countries were included. After a phosphate binder washout period, 255 patients were randomized in a 1:1 fashion. Two hundred and four patients completed the study per protocol (CaMg, N = 105; dropouts N = 18; sevelamer-HCl, N = 99; dropouts N = 34). Patient baseline characteristics were similar in both groups.

RESULTS

Serum phosphorus levels had decreased significantly with both drugs at week 25, and the study hypothesis of CaMg not being inferior to sevelamer-HCl was confirmed. The area under the curve for serum phosphorus (P = 0.0042) and the number of visits above K/DOQI (≤1.78 mmol/L, P = 0.0198) and Kidney disease: Improving global outcomes (KDIGO) targets (≤1.45 mmol/L, P = 0.0067) were significantly lower with CaMg. Ionized serum calcium did not differ between groups; total serum calcium increased in the CaMg group (treatment difference 0.0477 mmol/L; P = 0.0032) but was not associated with a higher risk of hypercalcaemia. An asymptomatic increase in serum magnesium occurred in CaMg-treated patients (treatment difference 0.2597 mmol/L, P < 0.0001). There was no difference in the number of patients with adverse events.

CONCLUSION

CaMg was non-inferior to the comparator at controlling serum phosphorus levels at Week 25. There was no change in ionized calcium; there was minimal increase in total serum calcium and a small increase in serum magnesium. It had a good tolerability profile and thus may represent an effective treatment of hyperphosphataemia.

Benefits and harms of phosphate binders in CKD: a systematic review of randomized controlled trials

BACKGROUND

Phosphate binders are widely used to control serum phosphorus levels in patients with chronic kidney disease (CKD). We analyzed the effects of phosphate binders on biochemical and patient-level end points in patients with CKD.

STUDY DESIGN

Systematic review and meta-analysis by searching MEDLINE (1966 to April 2009), EMBASE (1980 to April 2009), and the Cochrane Renal Group Specialised Register and the Cochrane Central Register of Controlled Trials (CENTRAL).

SETTING & POPULATION

Patients with CKD.

SELECTION CRITERIA FOR STUDIES

Randomized controlled trials.

INTERVENTION

Phosphate binders.

OUTCOMES

Serum phosphorus, calcium, and parathyroid hormone levels; incidence of hypercalcemia; all-cause mortality; adverse effects.

RESULTS

40 trials (6,406 patients) were included. There was no significant decrease in all-cause mortality (10 randomized controlled trials; 3,079 patients; relative risk [RR], 0.73; 95% confidence interval [CI], 0.46 to 1.16), hospitalization, or end-of-treatment serum calcium-phosphorus product levels with sevelamer compared with calcium-based agents. There was a significant decrease in end-of-treatment phosphorus and parathyroid hormone levels with calcium salts compared with sevelamer and a significant decrease in risk of hypercalcemia (RR, 0.47; 95% CI, 0.36 to 0.62) with sevelamer compared with calcium-based agents. There was a significant increase in risk of gastrointestinal adverse events with sevelamer in comparison to calcium salts (RR, 1.39; 95% CI, 1.04 to 1.87). Compared with calcium-based agents, lanthanum significantly decreased end-of-treatment serum calcium and calcium-phosphorus product levels, but with similar end-of-treatment phosphorus levels. Effects of calcium acetate on biochemical end points were similar to those of calcium carbonate. Existing data are insufficient to conclude for a differential impact of any phosphate binder on cardiovascular mortality or other patient-level outcome.

LIMITATIONS

Few long-term studies of the efficacy of phosphate binders on mortality and musculoskeletal morbidity, significant heterogeneity for many surrogate outcomes, and suboptimal reporting of study methods to determine trial quality.

CONCLUSION

Currently, there are insufficient data to establish the comparative superiority of non-calcium-binding agents over calcium-containing phosphate binders for such important patient-level outcomes as all-cause mortality and cardiovascular end points. Additional trials are still required to examine the differential effects of phosphate-binding agents on these end points and the mineral homeostasis pathway.

Phosphate binders in chronic kidney disease and end-stage renal disease: a patient-centered approach

Disorders of calcium and phosphorus metabolism are associated with significant morbidity and mortality in patients with advanced chronic kidney disease. These patients typically require oral phosphate binders to maintain phosphorus homeostasis, but the choice of which among several agents to use has been actively investigated and debated. Recent debate has been polarized between those who favor calcium-based binders for their proven efficacy and relatively low cost and those who favor sevelamer for its putative beneficial effects on inflammatory biomarkers and vascular calcification. This review summarizes the current state of the art of prescribing phosphate binders, ranging from large-scale clinical trials to focused mechanistic studies, and proposes that the available evidence does not conclusively prove the relative superiority of any one binder.

Minimizing bone abnormalities in children with renal failure

Renal osteodystrophy (ROD), a metabolic bone disease accompanying chronic renal failure (CRF), is a major clinical problem in pediatric nephrology. Growing and rapidly remodeling skeletal systems are particularly susceptible to the metabolic and endocrine disturbances in CRF. The pathogenesis of ROD is complex and multifactorial. Hypocalcemia, phosphate retention, and low levels of 1,25 dihydroxyvitamin D(3) related to CRF result in disturbances of bone metabolism and ROD. Delayed diagnosis and treatment of bone lesions might result in severe disability. Based on microscopic findings, renal bone disease is classified into two main categories: high- and low-turnover bone disease. High-turnover bone disease is associated with moderate and severe hyperparathyroidism. Low-turnover bone disease includes osteomalacia and adynamic bone disease. The treatment of ROD involves controlling serum calcium and phosphate levels, and preventing parathyroid gland hyperplasia and extraskeletal calcifications. Serum calcium and phosphorus levels should be kept within the normal range. The calcium-phosphorus product has to be <5 mmol(2)/L(2) (60 mg(2)/dL(2)). Parathyroid hormone (PTH) levels in children with CRF should be within the normal range, but in children with end-stage renal disease PTH levels should be two to three times the upper limit of the normal range. Drug treatment includes intestinal phosphate binding agents and active vitamin D metabolites. Phosphate binders should be administered with each meal. Calcium carbonate is the most widely used intestinal phosphate binder. In children with hypercalcemic episodes, sevelamer, a synthetic phosphate binder, should be introduced. In children with CRF, ergocalciferol (vitamin D(2)), colecalciferol (vitamin D(3)), and calcifediol (25-hydroxyvitamin D(3)) should be used as vitamin D analogs. In children undergoing dialysis, active vitamin D metabolites alfacalcidol (1alpha-hydroxy-vitamin D(3)) and calcitriol (1,25 dihydroxyvitamin D(3)) are applied. In recent years, a number of new drugs have emerged that hold promise for a more effective treatment of bone lesions in CRF. This review describes the current approach to the diagnosis and treament of ROD.

Emerging strategies for lowering serum phosphorous in patients with end-stage renal disease

Hyperphosphataemia is a major problem in patients with chronic kidney disease as it has been associated with increased morbidity and mortality. Over the last four decades, different modalities have been applied to treat hyperphosphataemia with varying degrees of success. Unfortunately, treatment strategies have led to unforeseen complications. These have prompted the development of new classes of medications with potentially better efficacy and few short-term and long-term side effects. This article reviews the causes, mechanism and management of hyperphosphataemia.

The safety of phosphate binders

Disturbances of mineral metabolism occur during the early stages of chronic kidney disease. As renal function worsens, excess dietary phosphorus accumulates and blood levels increase, that can be clearly seen when the glomerular filtration rate has fallen below 30 ml/min/1.73 m2. In patients with end stage renal disease, standard dialysis (three times/week) falls far short of removing adequate amounts of absorbed phosphorus; therefore, hyperphosphataemia is found in the majority of these patients. Hyperphosphataemia has long been associated with progression of secondary hyperparathyroidism and renal osteodystrophy, it can also lead to soft-tissue and vascular calcification. Recent observational data have associated hyperphosphataemia with increased cardiovascular mortality among dialysis patients. Adequate control of serum phosphorus remains a cornerstone in the clinical management and, despite the growing amount of available therapeutic options, achievement of NFK/KDOQI targets for mineral metabolism remain poor. Several reasons may explain the failure to adequately treat hyperphosphataemia: poor compliance with diet and phosphate binder prescriptions are common causes. Also, factors related with cost, tolerance, palatability, safety and efficacy are important. In this article, the authors review the advantages and drawbacks of conventional and emerging therapies in phosphorous binding.

Hyperphosphatemia and phosphate binders

PURPOSE

The pathophysiology of hyperphosphatemia associated with end-stage renal disease and treatment with phosphate binders are discussed.

SUMMARY

Phosphorus is an essential element necessary for the normal function of the human body, required for skeletal construction and synthesis of DNA, proteins, and adenosine triphosphate. In healthy individuals, serum phosphorus concentrations are maintained between 2.5 and 4.5 mg/dL through diet and renal excretion. In renal insufficiency, phosphorus excretion declines and hyperphosphatemia develops. The body's compensation mechanisms cause secondary hyperparathyroidism and renal osteodystrophy. Phosphate binders provide an effective means for managing serum phosphate. Commercially available phosphate binders include calcium carbonate, calcium acetate, sevelamer, lanthanum, and, rarely, aluminum hydroxide. Because of aluminum's known toxicities, aluminum-based phosphate binders have a limited place in therapy. Calcium carbonate's benefits are seen over a narrow gastric pH range, thereby limiting the drug's utility. Calcium acetate is effective over a wide pH range. Other phosphate binders, including sevelamer hydrochloride and lanthanum carbonate, have recently entered the market, but their use remains controversial.

CONCLUSION

If left untreated, hyperphosphatemia can result in secondary hyperparathyroidism, renal osteodystrophy, and metastatic calcification of blood vessels and soft tissue. The treatment of hyperphosphatemia in patients with chronic renal failure includes dialysis, dietary phosphorus restrictions, phosphate-binding medications, and vitamin D analogs. Selection of phosphate binders should be based on patient characteristics, including serum phosphate, serum calcium, and intact parathyroid hormone concentrations, and patient tolerability.

Control of Hyperphosphatemia among Patients with ESRD

Derangements of mineral metabolism occur during the early stages of chronic kidney disease (CKD). Hyperphosphatemia develops in the majority of patients with ESRD and has long been associated with progression of secondary hyperparathyroidism and renal osteodystrophy. More recent observational data have associated hyperphosphatemia with increased cardiovascular mortality among dialysis patients. Adequate control of serum phosphorus remains a cornerstone in the clinical management of patients with CKD not only to attenuate the progression of secondary hyperparathyroidism but also possibly to reduce the risk for vascular calcification and cardiovascular mortality. These measures include dietary phosphorus restriction, dialysis, and oral phosphate binders. Dietary restriction is limited in advanced stages of CKD. Phosphate binders are necessary to limit dietary absorption of phosphorus. Aluminum hydroxide is an efficient binder; however, its use has been nearly eliminated because of concerns of toxicity. Calcium salts are inexpensive and have been used effectively worldwide as an alternative to aluminum. Concerns of calcium overload have led to the investigation of alternatives. Currently, only two Food and Drug Administration-approved noncalcium, nonaluminum binders are available. Sevelamer hydrochloride is an exchange resin and was not as effective as calcium acetate in meeting new guideline recommendations in one double-blind clinical trial. Lanthanum carbonate is a rare earth element and has been studied less extensively. Concerns of long-term administration and toxicity exist. Furthermore, these agents are significantly more expensive than calcium salts, which may contribute to patient noncompliance.

A comparison of clinically useful phosphorus binders for patients with chronic kidney failure

A comparison of clinically useful phosphorus binders for patients with chronic kidney failure. Over the past 30 years it has become apparent that hyperphosphatemia plays a major causative role across the entire spectrum of morbidity associated with advancing kidney dysfunction and failure. A large fraction (60% to 70%) of dietary phosphorus is absorbed and normally excreted by the kidneys. Ideally, as kidney function deteriorates, the net quantity of phosphorus absorbed from the GI tract should be proportionally reduced to match the decrease in kidney function. After initiation of chronic dialysis therapy, the absorbed phosphorus load should match the amount of phosphorus removed via dialysis plus any excreted by residual kidney function. Because it is very difficult to reduce dietary phosphorus to these levels, a variety of oral phosphorus binders have been employed. Currently available binders include alkaline aluminum, magnesium, and calcium salts (primarily calcium carbonate and calcium acetate), various iron salts, and the binding resin sevelamer hydrochloride. Lanthanum carbonate is the newest agent and will probably be released shortly. This review compares the theoretic and in vitro chemistry of these drugs with in vivo data obtained in both normal patients, and in patients with kidney failure. The clinical potency and potential toxicity of the binding agents are compared, and optimal drug administration strategies are also reviewed.

Secondary hyperparathyroidism in children with chronic renal failure: pathogenesis and treatment

Despite advances in the management of patients with chronic renal failure, histologic features associated with secondary hyperparathyroidism remain the predominant skeletal findings; however, over the last decade the prevalence of adynamic bone has increased in both adult and pediatric patients with chronic renal failure. The management of children with secondary hyperparathyroidism and mild to moderate chronic renal failure should be started early, and should include correction of hypocalcemia and metabolic acidosis, maintenance of age-appropriate serum phosphorus levels, and institution of vitamin D therapy when serum intact parathyroid hormone (PTH) measurements are elevated to maintain the blood levels within normal limits; however, in children undergoing chronic dialysis therapy, the current recommendation is to maintain the serum intact PTH levels at least 2-4 times the upper limits of normal to prevent the development of low bone turnover disease. Serum calcium, phosphorus, alkaline phosphatase, and PTH levels should be monitored frequently, especially in infants and very young children. Discontinuation or reduction of vitamin D should be considered when there is a rapid decline in PTH levels, persistent elevation in serum calcium and serum phosphorus levels, and a significant diminution in alkaline phosphatase levels. In addition, a reduction in the calcium concentration of the dialysis fluid, and judicious use of calcium-containing salts as phosphate binding agents should also be performed in these patients. Although not yet extensively used in pediatric patients with secondary hyperparathyroidism, several therapeutic alternatives, such as the less calcemic vitamin D analogs, including paricalcitol [19-nor-1,25-(OH)(2)D(2)] and doxercalciferol [1-alpha-(OH)(2)D(2)], calcimimetics, and the availability of a calcium-free, aluminum-free phosphate binder such as sevelamer hydrochloride and lanthanum carbonate, may play significant roles in the future management of children with secondary hyperparathyroidism to promote linear growth, prevent parathyroid gland hyperplasia, avoid calciphylaxis and, in the long run, avert vascular calcifications.

Hyperphosphataemia in renal failure: causes, consequences and current management

Hyperphosphataemia is prevalent among chronic renal failure and dialysis patients. It is known to stimulate parathyroid hormone and suppress vitamin D3 production, thereby inducing hyperparathyroid bone disease. In addition, it may independently contribute to cardiac causes of death through increased myocardial calcification and enhanced vascular calcification. Hyperphosphataemia is also associated with cardiac microcirculatory abnormalities. Therefore, phosphate control is of prime importance. It is important to control phosphate levels early in the course of chronic renal failure in order to avoid and treat secondary hyperparathyroidism, and cardiovascular and soft tissue calcifications. Dietetic restrictions are often difficult to follow long term. Because of its large sphere of hydration and the complex kinetics of phosphate elimination, phosphate is not easily removed by dialysis. Long, slow dialysis may be effective, but this needs logistics and acceptance by patients. Thus, oral phosphate binders are generally required to control serum levels. None of the existing phosphate binding agents is truly satisfactory. Aluminium-containing agents are highly efficient but many clinicians have abandoned their use because of the potential toxicity. Despite of the wide use of calcium-containing agents, there was a link with hypercalcaemia and soft tissue calcifications. Novel phosphate binders in the form of polyallylamine hydrochloride, polyuronic acid derivatives and lanthanum carbonate appear promising. In this review, we discuss causes of hyperphosphataemia, pathological consequences and modalities of treatment.

The nephrologist's role in the management of calcium-phosphorus metabolism in patients with chronic kidney disease

BACKGROUND

In patients with chronic kidney disease (CKD), timely referral to a nephrologist has been shown to improve outcomes, but the specific care measures mediating these superior outcomes have not been sufficiently described.

METHODS

In a cohort of 3014 patients with CKD, we evaluated whether they had any indicators of calcium-phosphorus metabolism management prior to renal replacement therapy (RRT). These included measurement of parathyroid hormone (PTH) or vitamin D metabolites, or receipt of calcitriol or calcium-containing phosphate binders (CCPB) prior to RRT. Control patients without such care were selected by risk-set matching. We used multivariate conditional logistic regression analysis to test whether use of these interventions was associated with prior nephrologist consultation. We then used Cox proportional hazards models to assess whether implementation of such care was associated with differences in 1-year mortality once RRT was instituted.

RESULTS

Only 3.4% of CKD patients had their PTH assessed prior to RRT, and 0.3% had vitamin D status measured. Use of calcitriol (12.2%) and CCPBs (16%) was slightly more prevalent. Seeing a nephrologist was highly associated with use of the tests and drugs studied (odds ratio, 1.28 to 6.46; all P values <0.001), but care by generalists or other specialists was not. Management of calcium-phosphorus metabolism was independently associated with a 35% decreased likelihood of death (hazards ratio=0.65; 95%CI, 0.51 to 0.84) in the first year of RRT.

CONCLUSION

Improvements in management of calcium-phosphorus metabolism in patients with CKD are attributable to nephrologist care and appear to mediate the survival benefit seen in patients who see a nephrologist relatively early in the course of their CKD.

Safety of New Phosphate Binders for Chronic Renal Failure

Phosphate (Pi) retention is a common problem in patients with chronic kidney disease, particularly in those who have reached end-stage renal disease (ESRD). In addition to causing secondary hyperparathyroidism and renal osteodystrophy, recent evidence suggests that, in ESRD patients, high serum phosphorus concentration and increased calcium and phosphorous (Ca x P) product are associated with vascular and cardiac calcifications and increased mortality. Dietary phosphorus restriction and Pi removal by dialysis are not sufficient to restore Pi homeostasis. Reduction of intestinal Pi absorption with the use of Pi binders is currently the primary treatment for Pi retention in patients with ESRD. The use of large doses of calcium-containing Pi binders along with calcitriol administration may contribute to over-suppression of parathyroid hormone secretion and adynamic bone disease as well as to a high incidence of vascular calcifications. When used in patients with impaired renal function, aluminium salts were found to accumulate in bone and other tissues, resulting in osteomalacia and encephalopathy.Sevelamer, an aluminium- and calcium-free Pi binder can reduce serum phosphorus concentration and is associated with a significantly lower incidence of hypercalcaemia, while maintaining the ability to suppress parathyroid hormone production. An additional benefit of sevelamer is its ability to lower low density lipoprotein-cholesterol and total cholesterol levels. Sevelamer attenuates the progression of vascular calcifications in haemodialysis patients, which may lead to lower mortality. The use of sevelamer in non-dialysed patients might aggravate metabolic acidosis, common in these patients. Several other calcium-free Pi binders are in development. Lanthanum carbonate has shown significant promise in clinical trials in ESRD patients. Magnesium salts do not offer a significant advantage over currently available Pi binders. Their use is restricted to patients receiving dialysis since excess magnesium must be removed by dialysis. Iron-based compounds have shown variable efficacy in short-term clinical trials in small numbers of haemodialysis patients. Mixed metal hydroxyl carbonate compounds have shown efficacy in animals but have not been studied in humans. Major safety issues include absorption of the metal component with possible tissue accumulation and toxicity.

Improved Strategies for the Treatment of Renal Osteodystrophy

Renal osteodystrophy (ROD) encompasses several distinct skeletal complications resulting from the metabolic abnormalities associated with chronic kidney disease (CKD). Other manifestations of altered calcium and phosphorus homeostasis include an increased risk of cardiovascular mortality and morbidity. Hyperphosphatemia and secondary hyperparathyroidism (HPT) are associated with these adverse events, and ultimately can lead to ROD. Dietary restriction of phosphorus, use of phosphate binding agents, and vitamin D therapy have been the mainstay of therapy for HPT. Recently, several new therapeutic agents have become available for the management of HPT. The nonelemental phosphate binder, sevelamer hydrochloride (Renagel®) has provided an alternative to calcium-containing binders for the management of hyperphosphatemia. This agent also decreases calcium load and minimizes the risk of hypercalcemia and skin and soft tissue calcifications. Research in the area of vitamin D receptors has lead to the development of vitamin D analogs including paricalcitol (Zemplar®) and doxercalciferol (Hectorol®) as alternative agents for HPT. Potential benefits of these analogs include a lower risk of hypercalcemia and hyperphosphatemia compared with calcitriol, although further evaluation is warranted as these agents are used more in clinical practice. Calcimimetics are also in the pipeline as potential agents for management of HPT by inhibition of parathyroid hormone secretion. These new developments in the management of metabolic disorders of CKD provide pharmacotherapeutic alternatives to improve patient outcomes and prevent/manage ROD. The challenge is to determine appropriate guidelines for use of these agents at all stages of CKD.

Hyperphosphatemia in end-stage renal disease

Hyperphosphatemia occurs universally in end-stage renal disease (ESRD) unless efforts are made to prevent positive phosphate balance. Positive phosphate balance results from the loss of renal elimination of phosphate and continued obligatory intestinal absorption of dietary phosphate. Increased efflux of phosphate from bone because of excess parathyroid hormone-mediated bone resorption can also contribute to increased serum phosphate concentrations in the setting of severe hyperparathyroidism. It is important to treat hyperphosphatemia because it contributes to the pathogenesis of hyperparathyroidism, vascular calcifications, and increased cardiovascular mortality in ESRD patients. Attaining a neutral phosphate balance, which is the key to the management of hyperphosphatemia in ESRD, is a challenge. Control of phosphorus depends on its removal during dialysis and the limitation of gastrointestinal absorption by dietary phosphate restriction and chelation of phosphate. Knowledge of the quantitative aspects of phosphate balance is useful in optimizing our use of phosphate binders, dialysis frequency, and vitamin D sterols. The development of new phosphate binders and efforts to find new ways to inhibit gastrointestinal absorption of phosphate will lead to improvements in the control of serum phosphate levels in ESRD.

Compounds in development to combat hyperphosphataemia

Hyperphosphataemia in haemodialysis patients is associated with secondary hyperparathyroidism and more importantly with an increased cardiovascular mortality in dialysed patients. Removal of phosphate during dialysis is less than net intestinal uptake. This imbalance results in a positive phosphate balance. To control serum phosphate concentration oral phosphate binders have to be taken to reduce net intestinal uptake. The use of classical phosphate binders such as calcium carbonate, calcium acetate and aluminium-containing phosphate binders is limited by their side effects. Hypercalcaemia aggravates vascular calcification and cardiovascular risk. Aluminium intoxication causes aluminium osteopathy, anaemia and encephalopathy. Therefore, the development of calcium- and aluminium free phosphate binders has become a challenge to clinical nephrology. Polyallylamine hydrochloride (sevelamer) is one of the new alternative compounds which has been shown to effectively bind phosphate in dialysis patients. A promising approach in the development of alternative phophate binders are trivalent-iron (Fe(III)) containing phosphate binders. They were not only successfully tested in experimental animals but have also been shown to reduce urinary phosphate excretion and serum phosphate concentrations in patients with preterminal failure and those on maintenance haemodialysis. This review outlines the experimental and clinical data on Fe-III based phosphate binders providing evidence that they will be as effective and safe as phosphate binders without the major side effects of classical phosphate-binding compounds.

Prevention of renal osteodystrophy in predialysis patients

Impaired calcitriol synthesis is one of the major factors contributing to the development of secondary hyperparathyroidism in patients with chronic renal failure. Vitamin D therapy, particularly 1alpha-hydroxyvitamin D3, even in low doses, has been shown to be effective in the treatment of secondary hyperparathyroidism in patients with mild-to-moderate chronic renal failure. Complications associated with calcitriol and alfacalcidol therapy, which include hypercalcemia and progressive deterioration of renal function, have been reported in some patients. The majority of the studies reviewed, however, demonstrated that daily calcitriol and alfacalcidol doses below 0.25 microg are rarely associated with hypercalcemia, hyperphosphatemia, or progressive decline in renal function. In addition, these complications usually resolve with the reduction in dose or discontinuation of the medication. Thus, vitamin D therapy may be valuable in the treatment of patients with mild-to-moderate chronic renal failure who may be at high risk of developing secondary hyperparathyroidism.

Calcium acetate versus calcium carbonate as oral phosphate binder in pediatric and adolescent hemodialysis patients

Calcium carbonate is widely used as an oral phosphorus binder to control hyperphosphatemia in children on maintenance hemodialysis. Intestinal calcium absorption may induce hypercalcemia, particularly if calcitriol is given simultaneously. In adults, calcium acetate binds phosphorus more effectively than calcium carbonate, while reducing the frequency of hypercalcemic events. We therefore compared calcium acetate with calcium carbonate in nine pediatric patients on long-term maintenance hemodialysis. Following a 1-week withdrawal of phosphorus binders, calcium carbonate was administered for 7 weeks; after a second withdrawal, calcium acetate was given for another 7 weeks. All patients received calcitriol regularly. Both agents lowered the serum phosphorus concentration significantly (calcium carbonate 5.7 +/- 1.4 vs. 7.7 +/- 2.1 mg/ dl, P < 0.005; calcium acetate 5.8 +/- 1.4 vs. 7.8 +/- 2.0 mg/dl, P < 0.005). Significantly less elementary calcium was ingested with calcium acetate than with calcium carbonate: 750 (375-1,500) vs. 1,200 (0-3,000) mg calcium/day, P < 0.0001. Wit calcium carbonate serum calcium increased significantly. The number of episodes of hyperphosphatemia or hypercalcemia did not differ between treatments. Intact plasma parathyroid hormone (PTH) decreased significantly with both phosphate binders, and serum 25-hydroxyvitamin D3 increased. There was a close relationship between serum phosphorus and PTH in prepubertal but not in pubertal patients. We conclude that hyperphosphatemia can be controlled effectively by both calcium acetate and calcium carbonate in pediatric hemodialysis patients. The oral load of elementary calcium is reduced significantly by binding phosphorus with calcium acetate instead of calcium carbonate; nevertheless, hypercalcemic episodes remain equally frequent with both phosphate binders.

The renal bone diseases in children treated with dialysis

Renal osteodystrophy represents a spectrum from high- to low-turnover bone lesions. The specific pattern, however, may change during selected therapeutic interventions. As in the past, osteitis fibrosa remains the most frequent histologic lesion in pediatric patients on dialysis, although recently the prevalence of low-turnover bone lesions without aluminum toxicity has been increasing in the pediatric population. This may be a consequence of aggressive calcitriol and calcium therapy. The different factors involved in the development of secondary hyperparathyroidism include hyperphosphatemia, hypocalcemia, altered vitamin D synthesis, impairments in parathyroid hormone (PTH) secretion and metabolism, and, recently, possible downregulation of renal PTH/PTH-rP messenger RNA receptor. New developments in molecular biology have demonstrated the relationship between vitamin D and PTH. The use of high-dose pulse intravenous, intraperitoneal, and oral calcitriol therapy has significantly decreased serum PTH levels and retarded the progression of osteitis fibrosa. These therapeutic interventions, however, may have led to the development of adynamic bone lesions. The impact of adynamic bone lesions in the young and growing skeleton remains to be determined.

Magnesium carbonate as a phosphorus binder: a prospective, controlled, crossover study

The use of calcium carbonate (CaCO3) to bind phosphorus (P) in chronic hemodialysis patients has been a popular tactic in the past decade. Nonetheless, problems with hypercalcemia decrease its usefulness, particularly in patients treated with calcitriol. A P binder not containing calcium (Ca) would be of value in these circumstances. In short-term studies, we showed that magnesium carbonate (MgCO3) was well-tolerated and controlled P and Mg levels when given in conjunction with a dialysate Mg of 0.6 mg/dl. We, therefore, performed a prospective, randomized, crossover study to evaluate if the chronic use of MgCO3 would allow a reduction in the dose of CaCO3 and yet achieve acceptable levels of Ca, P, and Mg. We also assessed whether the lower dose of CaCO3 would facilitate the use of larger doses of calcitriol. The two phases were MgCO3 plus half the usual dose of CaCO3 and CaCO3 alone given in the usual dose. It was found that MgCO3 (dose, 465 +/- 52 mg/day elemental Mg) allowed a decrease in the amount of elemental Ca ingested from 2.9 +/- 0.4 to 1.2 +/- 0.2 g/day (P < 0.0001). The Ca, P, Mg levels were the same in the two phases. The maximum dose of i.v. calcitriol without causing hypercalcemia was 1.5 +/- 0.3 micrograms/treatment during the MgCO3 phase and 0.8 +/- micrograms/treatment during the Ca phase (P < 0.02). If these studies are confirmed, the use of MgCO3 and a dialysate Mg of 0.6 mg/dl may be considered in selected patients who develop hypercalcemia during treatment with i.v. calcitriol and CaCO3.

Bone and mineral metabolism in childhood end-stage renal disease

Renal osteodystrophy represents a spectrum from high to low turn-over lesions of bone, and the specific pattern may change during the evolution of chronic renal failure and as a consequence of specific therapeutic interventions. Although secondary hyperparathyroidism remains the predominant histologic lesion in patients undergoing maintenance dialysis, recent evidence indicates higher frequency of adynamic lesion not associated with aluminum intoxication. The different factors involved in the development of each of the histologic subtypes have been described together with the clinical manifestations of renal bone disease in childhood. Avoidance of aluminum-containing medications and the intermittent administration of calcitriol are effective approaches for the management of the renal bone diseases. The long-term consequences of the adynamic lesion remain to be determined.

The importance of dosing intravenous calcitriol in dialysis patients with severe hyperparathyroidism

The current study evaluates the use of intravenous (IV) calcitriol in 10 patients with severe hyperparathyroidism (HPTH). Patients with parathyroid hormone (PTH) > 1,200 pg/m and serum P < 6.5 mg/dL were studied. Ten patients with a mean PTH of 1,826 +/- 146 pg/mL were treated for a mean of 48 weeks with a dose of IV calcitriol commensurate to the level of PTH. The initial calcitriol dose had to be increased in seven patients. The mean maximum dose of calcitriol was 3.8 micrograms thrice weekly. There was a dramatic decrease in PTH levels, and by the end of the study it was 211 +/- 48 pg/mL. Alkaline phosphatase decreased from 582 +/- 3 to 120 +/- 12 IU/L. Serum Ca and P remained unchanged in most patients. There were three episodes of hyperphosphatemia in one patient, and another had a hypercalcemic episode. In conclusion, patients with severe HPTH respond very well to IV calcitriol, provided that dosing of calcitriol is commensurate to PTH levels, and hyperphosphatemia is kept under control.

A new analog of calcitriol, 19-nor-1,25-(OH)2D2, suppresses parathyroid hormone secretion in uremic rats in the absence of hypercalcemia

The active metabolite of vitamin D, calcitriol (1 alpha,25-(OH)2D3), suppresses parathyroid hormone (PTH) gene transcription. Although 1 alpha,25-(OH)2D3 is effective in suppressing secondary hyperparathyroidism (SH) in uremic patients, the mandatory use of large amounts of calcium salts to control serum phosphorus may preclude, in some patients, the use of ideal therapeutic doses of 1 alpha,25-(OH)2D3 because of hypercalcemia. We have studied a new analog of calcitriol, 19-nor-1 alpha,25-(OH)2D2, that possesses low calcemic and phosphatemic activity. Uremic rats received vehicle, 1 alpha,25-(OH)2D3 (2.0, 4.0, or 8.0 ng/rat) or 19-nor-1,25-(OH)2D2 (8.0, 25 or 75 ng/rat) intraperitoneally (IP) every other day for a period of 8 days. Pretreatment and posttreatment values of intact PTH were measured. The normal values for rat intact-PTH were 22 +/- 4.2 pg/mL and for ionized calcium (ICa) 4.77 +/- .07 mg/dL. The only dose of 1 alpha,25-(OH)2D3 that achieved a significantly, suppressed PTH (P < 0.01) was the 8.0 ng/rat. PTH decreased from 202 +/- 31 to 90 +/- 20 pg/mL. However, ICa increased from 4.81 +/- 0.08 to 5.08 mg/dL from uremic control (P < 0.02). Conversely, all doses of 19-nor-1,25-(OH)2D2 were effective in suppressing PTH, and none produced an elevation in ICa that was significantly different from that of vehicle-treated uremic rats. The maximum effect was achieved with the 75 ng/rat dose, which decreased PTH from 193 +/- 49 to 53 +/- 16 pg/mL (a decrease in 72.5%).(ABSTRACT TRUNCATED AT 250 WORDS)

Low dialysate calcium in continuous ambulatory peritoneal dialysis: a randomized controlled multicenter trial. The Peritoneal Dialysis Multicenter Study Group

Hypercalcemia is a common complication in continuous ambulatory peritoneal dialysis (CAPD) patients treated with calcium-containing phosphate binders and using the standard dialysate calcium concentration of 3.5 mEq/L (SCa). Lowering the dialysate calcium was proposed to overcome this problem. The current randomized controlled multicenter study was designed to investigate efficiency and safety of a low calcium dialysate (2.00 mEq/L; LCa) compared with SCa (3.5 mEq/L) in CAPD patients. After an 8-week run-in period, 103 stable CAPD patients, 68 men, 35 women, aged 54.5 years (range, 20 to 77)) were randomly allotted to treatment with either LCa or SCa. All patients received calcium carbonate as oral phosphate binder to achieve serum phosphate levels < 6.2 mg/dL. If persistent hypercalcemia arose, CaCO3 was replaced by Al(OH)3 until normocalcemia was achieved. All patients received 0.25 microgram calcitriol/d. Parameters monitored included total and ionized serum calcium, serum phosphate, phosphate binder intake, incidence of hypercalcemia, serum aluminium, intact parathyroid hormone (1,84PTH), osteocalcin, alkaline phosphatase, bone mineral density and hand skeletal x-ray. Primary end points were (a) number of hypercalcemic episodes, (b) tolerated doses of calcium-containing phosphate binders, and (c) 1,84PTH. After 6 months of therapy, total and ionized calcium were lower in LCa patients (total Ca:9.6 v 10.08 mEq/L, P = 0.005; iCa: 4.76 v 5.15 mg/dL; P = 0.013). In the LCa group, significantly fewer episodes of hypercalcemia were recorded (total S-calcium > 10.8 mg/dL: LCa 24 v SCa 86 episodes; P < 0.005). Use of LCa permitted the administration of more CaCO3 (mean daily tablet number: LCa, 5.9 v SCa, 4.2; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium kinetics and the long-term effects of lowering dialysate calcium concentration

The optimal dialysate calcium (Ca) content for hemodialysis has been classically fixed at 1.75 mM. However, this dialysate Ca concentration (dCa) with its positive intradialytic Ca balance combined with the use of CaCO3 as a phosphate binder may result in hypercalcemia. To prevent or treat hypercalcemia, a decrease in dCa has been proposed. In the present study both the acute and the long-term effects of lowering dCa were assessed. Additionally, given the results obtained after one year with low dCa the effectiveness of i.v. 1 alpha vitamin D3 in lowering PTH serum levels in two groups of patients dialyzed with different dCa was also studied. (a) Ca kinetics during hemodialysis (HD) and on line hemodiafiltration (HDF) were studied in a group of nine stable patients who were sequentially treated with 1.75, 1.5 and 1.25 mM dCa. Dialysate was the same but for the dCa which was lowered stepwise. Na, K, tCa, ionized Ca (iCa), proteins, phosphate and pH were measured from blood inlet and outlet and dialysate outlet at the start, one hour, two hours and after the treatments. At the same time weight, blood pressure and heart rate were recorded. The sieving of iCa was significantly different in HDF versus HD (F = 6.73; P < 0.01); intravenous infusion of 18 liters of filtered ultrapure dialysate compensated the Ca loss due to the convective component of HDF, as iCa was similar at the blood inlet in HD and HDF in the three dCa tested (F = 2.59; NS). Intradialytic iCa kinetics measured in the blood inlet were significantly different with different dCa (P < 0.001 for 1.75 mM vs. 1.5 mm and P < 0.001 for 1.5 mM vs. 1.25 mM). A significant increase in post-dialysis iCa was observed with dCa of 1.75 and 1.5 while no modification was observed with 1.25 mM dCa. (b) Regarding long-term effects of lowering dCa, seven of the nine patients acutely studied were followed for a one year period after changing from dCa = 1.5 to dCa = 1.25 mM. A control group of six patients was maintained with dCa = 1.5 for the same period of time and with the same treatment schedule but for dCa. Total Ca, phosphate and alkaline phosphatase were assessed monthly, and phosphate binders and oral vitamin D derivative doses were adapted accordingly. Intact PTH was determined quarterly. CaCO3 oral intake was more than doubled in the low dCa group. Total Ca, phosphate and ALP were similar in both groups over the assessed year.(ABSTRACT TRUNCATED AT 400 WORDS)

Reduced risk of hypercalcemia for hemodialysis patients by administering calcitriol at night

Renal osteodystrophy therapy in dialysis patients with calcitriol and intestinal phosphate binders containing calcium entails the risk of hypercalcemia. A study was performed using 35 hemodialysis patients to see whether the time of day when calcitriol is administered influences the incidence of hypercalcemia. It was shown that simply by administering at night (11:00 PM), the occurrence of hypercalcemia was significantly reduced. While greater than 80% of patients developed hypercalcemia when calcitriol was administered in the morning, when administered at night, this figure was only 50% (P less than 0.013). At the same time, the extent of hypercalcemia when calcitriol was administered at night was significantly lower than when it was administered in the morning. The incidence of hypercalcemia occurred regardless of the type of phosphate binder containing calcium used, whether it was calcium acetate or calcium carbonate. In addition, hypercalcemic episodes were always associated with hyperphosphatemia. On the basis of the above information, it would be expedient to administer calcitriol at night to dialysis patients, in order to reduce the risk of hypercalcemia and to preserve the hypophosphatemic effect of the applied intestinal phosphate binders.

Hyperphosphatemia: its consequences and treatment in patients with chronic renal disease

Control of phosphorus accumulation in chronic renal insufficiency is crucial to the prevention of secondary hyperparathyroidism and metastatic calcification. In early renal failure, calcitriol levels are normal and parathyroid hormone levels are elevated. The phosphorus levels are maintained in the normal range by the phosphaturia induced by hyperparathyroidism. In this situation, dietary phosphorus restriction increases calcitriol levels and suppresses parathyroid hormone secretion. As renal failure progresses into late stages, hyperphosphatemia is evident along with low levels of calcitriol and worsening hyperparathyroidism. Phosphorus restriction will not affect calcitriol concentrations, yet parathyroid levels may decline. During long-term dialysis, urinary excretion of phosphorus is usually minimal. Therefore, phosphorus balance is determined primarily by the net amount absorbed by the bowel and the quantity removed during dialytic therapy. Given an adequate diet, no form of conventional dialysis is able to fully compensate for the gastrointestinal absorption of phosphorus. Hence, compounds that bind phosphorus in the bowel are often necessary. With the realization that the use of phosphorus binders containing aluminum leads to aluminum accumulation and its sequelae: osteomalacia, dementia, myopathy, and anemia, other phosphorus binders have been evaluated. Calcium carbonate has been investigated the most thoroughly and is in wide use. It is inexpensive and contains a high percent of elemental calcium. However, it is only modestly potent in the binding of phosphorus, and large doses are often necessary to attain satisfactory control of phosphorus. This may lead to hypercalcemia. One approach to this problem is to decrease the concentration of calcium in the dialysate. Alternatively, a more effective phosphorus binder may be used. Calcium acetate has been shown in acute studies to have twice the binding capacity of phosphorus per calcium absorbed than calcium carbonate. Whether use of this compound decreases the incidence of hypercalcemia is unproven. Calcium citrate increases the gastrointestinal absorption of aluminum and offers no advantage over calcium carbonate. Other compounds, such as calcium ketoacids and calcium alginate, have not been extensively studied and are not generally available. The use of phosphorus binders containing magnesium in conjunction with a dialysate low in magnesium may be efficacious. Large doses of magnesium will cause diarrhea and thus limit its use as a single agent. Reasons for failure to control hyperphosphatemia include poor compliance, improper prescription of binders, poor dissolution rates seen with some generic brands of calcium carbonate, and the presence of severe hyperparathyroidism. Optimal control of serum phosphorus in dialysis patients should always be viewed in the context of adequate nutrition and protein intake.