Lanthanum Carbonate Is an Effective Hypophosphatemic Agent for Hemodialysis Patients Intolerant of Other Phosphate Binders

An update on phosphate binders for the treatment of hyperphosphatemia in chronic kidney disease patients on dialysis: a review of safety profiles

INTRODUCTION

Hyperphosphatemia is an inevitable complication for patients undergoing dialysis, as is the resulting need for treatment with phosphate binders. Currently, various phosphate binders are clinically available. In addition to their phosphate-lowering activity, individual phosphate binders have differing safety profiles and off-target actions.

AREAS COVERED

This paper reviews the safety of phosphate binders and issues to be resolved.

EXPERT OPINION

Calcium-based phosphate binders are well tolerated but may increase calcium overload risk. Sevelamer reduces serum cholesterol levels and exerts anti-inflammatory effects. Compared to sevelamer, bixalomer is associated with fewer gastrointestinal symptoms. Aluminum-containing binders, lanthanum carbonate, and sucroferric oxyhydroxide exhibit strong phosphate-lowering activity. Although ferric citrate reduces erythropoiesis-stimulating agents and intravenous iron doses, its use requires monitoring of iron metabolic markers to avoid overload. Occasionally, combined use of multiple phosphate binders can offer the advantages of each phosphate binder while minimizing their drawbacks; thus, this may be desirable according to individual patients' conditions and comorbidities. However, increased pill burden and nonadherence to phosphate binders emerge as new problems. We expect that novel therapeutic strategies will be developed to resolve these issues.

Phosphate balance in ESRD: diet, dialysis and binders against the low evident masked pool

Phosphate metabolism is crucial in the pathophysiology of secondary hyperparathyroidism and vascular calcification. High phosphate levels have been consistently associated with unfavorable outcomes in dialysis patients, but several limitations are still hampering a resolutive definition of the optimal targets of phosphate serum levels to be achieved in this cohort. Nonetheless, hyperphosphatemia is a late marker of phosphate overload in humans. Clinical nephrologists routinely counteract the positive phosphate balance in dialysis patients through nutritional counseling, stronger phosphate removal by dialysis and prescription of phosphate binders. However, the superiority against placebo of phosphate control by diet, dialysis or binders in terms of survival has never been tested in dedicated randomized controlled trials. The present review discusses this conundrum with particular emphasis on the rationale supporting the value of a simultaneous intervention against phosphate overload in dialysis patients via the improvement of dietary intakes, dialysis efficiency and an individualized choice of phosphate binders.

Emerging effects of sevelamer in chronic kidney disease

Sevelamer, a non-absorbable anion exchange resin, is used to control hyperphosphatemia in chronic kidney disease (CKD) by binding to dietary phosphate in the gastrointestinal tract. Lipid-lowering effect is a widely recognized pleiotropic effect of sevelamer. In addition, many studies have reported that sevelamer leads to reduced vascular calcification compared with calcium-containing phosphate binders, which is attributed to the improved lipid profiles and decreased calcium load. In addition, recent studies have suggested novel pleiotropic effects on bone structure, inflammation, oxidative stress, anemia, fetuin-A, and trace element metabolism in CKD patients. All of these effects have the potential to suppress the development/progression of cardiovascular lesions and reduce mortality. This review summarizes novel findings from recent studies and discusses the potential pleiotropic effects of sevelamer on non-traditional cardiovascular risk factors in CKD patients.

Phosphorus and nutrition in chronic kidney disease

Patients with renal impairment progressively lose the ability to excrete phosphorus. Decreased glomerular filtration of phosphorus is initially compensated by decreased tubular reabsorption, regulated by PTH and FGF23, maintaining normal serum phosphorus concentrations. There is a close relationship between protein and phosphorus intake. In chronic renal disease, a low dietary protein content slows the progression of kidney disease, especially in patients with proteinuria and decreases the supply of phosphorus, which has been directly related with progression of kidney disease and with patient survival. However, not all animal proteins and vegetables have the same proportion of phosphorus in their composition. Adequate labeling of food requires showing the phosphorus-to-protein ratio. The diet in patients with advanced-stage CKD has been controversial, because a diet with too low protein content can favor malnutrition and increase morbidity and mortality. Phosphorus binders lower serum phosphorus and also FGF23 levels, without decreasing diet protein content. But the interaction between intestinal dysbacteriosis in dialysis patients, phosphate binder efficacy, and patient tolerance to the binder could reduce their efficiency.

Randomized crossover study of the efficacy and safety of sevelamer hydrochloride and lanthanum carbonate in Japanese patients undergoing hemodialysis

Insufficient control of serum calcium and phosphate levels in patients undergoing hemodialysis is associated with increased mortality. As commonly used calcium-containing phosphate binders can cause arterial calcification, newly developed calcium-free phosphate binders, such as sevelamer hydrochloride (SH) and lanthanum carbonate (LC), have received much attention. We assessed the efficacy and safety of SH and LC treatment in Japanese patients undergoing hemodialysis in a prospective randomized open blinded endpoint (PROBE) crossover study. Forty-two patients were randomized to receive SH or LC for 13 weeks, with the dosages adjusted every 2 weeks, followed by treatment with the other drug for another 13 weeks. The average daily doses of SH and LC were 2971 ± 1464 mg and 945 ± 449 mg, respectively. The mean dosage ratio of SH to LC was 3.05, which was maintained throughout the treatment period. SH and LC were similarly effective at controlling serum calcium and phosphate levels in the majority of patients (78-93%). A few serious adverse events (AEs) involving the biliary system occurred during the LC treatment period, but they were not considered to be treatment-induced. Although the incidence of constipation, the most common treatment-related AE, was higher during the SH period (27% vs. 5%; P < 0.05), no difference was observed in total treatment-related AEs. This study demonstrates that SH and LC are comparable treatments for controlling serum phosphate and calcium levels, and that both compounds are safe and well-tolerated in Japanese patients undergoing hemodialysis.

Measurement of serum lanthanum in patients treated with lanthanum carbonate by inductively coupled plasma-mass spectrometry

Background

Lanthanum carbonate is used as a phosphate binder in patients with stage V chronic kidney disease (CKD). While well tolerated in clinical trials, with no toxicity reported as regards bone and liver metabolism, and cognitive function, concerns remain over possible toxicity. Published methods for the measurement of lanthanum ion in biological samples include aggressive and complicated sample preparation steps that are unsuitable for routine use. A simple method has been developed and validated for the measurement of serum lanthanum.

Method

A ThermoFisher Scientific XSERIES-II inductively coupled plasma-mass spectrometer was used to monitor 139La. Validation was undertaken using internal quality control solutions containing lanthanum ion (0.20, 0.70 and 4.00 μg/L). Lanthanum was measured in patients (number = 20) with CKD prescribed lanthanum carbonate (500–1500 mg/d) and patients undergoing haemodialysis not prescribed lanthanum carbonate (number = 20).

Results

Accuracy and imprecision were >95% and <5%, respectively. Calibration was linear (range 0.1–5 μg/L, R2 = 0.99). The lower limit of quantification (LLoQ) was 0.1 μg/L lanthanum ion. In patients with CKD not prescribed lanthanum carbonate, serum lanthanum was below the LLoQ. Out of 20 CKD patients prescribed lanthanum carbonate, serum lanthanum was measurable in only 12 (range 0.11–0.60 μg/L lanthanum ion). There was no apparent relationship between dose and serum lanthanum in these patients.

Conclusions

A lack of relationship between the dose of lanthanum carbonate and the serum lanthanum concentration may have been due to poor adherence to the treatment regimen. However the concentrations measured were close to the LLoQ.

Clinical usefulness of lanthanum carbonate for serum phosphate control in difficult patients

BACKGROUND

The adequate control of phosphataemia is of major importance in end-stage renal disease patients on maintenance dialysis. Recently, lanthanum carbonate (LC) has been added to the phosphate binder armamentarium. To our knowledge, no studies have yet evaluated the usefulness of this drug in uncontrolled hyperphosphataemic patients.

METHODS

This was a 6-month prospective observational study. Patients on chronic hemodialysis who had previously failed to achieve serum phosphate control were enrolled. Thirty-four patients (i.e. 11% out of 305 from three dialysis units) met the inclusion criteria. Lanthanum carbonate was introduced and titrated to achieve serum phosphate control, according to the KDOQI guidelines. Clinical targets, gastrointestinal symptoms, and patients' satisfaction with therapy were assessed at baseline and after 6 months.

RESULTS

Eight patients (23.5%) were withdrawn from the study due to side effects. In the remaining patients, serum phosphate level significantly decreased from 5.8 to 4.4 mg/dl and calcium-phosphate product also decreased significantly from 55.6 to 41.8 mg(2)/dl(2). The average number of all phosphate binder tablets taken per day was reduced from 6.7 to 4.7. Evaluation scores of dyspeptic symptoms and of patient's satisfaction with therapy also improved: from 7.5 to 5.3 and from 6.6 to 8.1, respectively.

CONCLUSIONS

The introduction of LC improved serum phosphate control in over 70% of these "difficult patients". A lower pill burden was also obtained, which might help to simplify treatment and increase patients' compliance. Dyspeptic symptoms and overall satisfaction with treatment also improved.

Developmental and regional patterns of GAP-43 immunoreactivity in a metamorphosing brain

Growth-associated protein-43 is typically expressed at high levels in the nervous system during development. In adult animals, its expression is lower, but still observable in brain areas showing structural or functional plasticity. We examined patterns of GAP-43 immunoreactivity in the brain of the bullfrog, an animal whose nervous system undergoes considerable reorganization across metamorphic development and retains a strong capacity for plasticity in adulthood. Immunolabeling was mostly diffuse in hatchling tadpoles, but became progressively more discrete as larval development proceeded. In many brain areas, intensity of immunolabel peaked at metamorphic climax, the time of final transition from aquatic to semi-terrestrial life. Changes in intensity of GAP-43 expression in the medial vestibular nucleus, superior olivary nucleus, and torus semicircularis appeared correlated with stage-dependent functional changes in processing auditory stimuli. Immunolabeling in the Purkinje cell layer of the cerebellum and in the cerebellar nucleus was detectable at most developmental time points. Heavy immunolabel was present from early larval stages through the end of climax in the thalamus (ventromedial, anterior, posterior, central nuclei). Immunolabel in the tadpole telencephalon was observed around the lateral ventricles, and in the medial septum and ventral striatum. In postmetamorphic animals, immunoreactivity was confined mainly to the ventricular zones and immediately adjacent cell layers. GAP-43 expression was present in olfactory, auditory and optic cranial nerves throughout larval and postmetamorphic life. The continued expression of GAP-43 in brain nuclei and in cranial nerves throughout development and into adulthood reflects the high regenerative potential of the bullfrog's central nervous system.