The phosphate binder equivalent dose.

Phosphate binders include calcium acetate or carbonate, sevelamer hydrochloride or carbonate, magnesium and lanthanum carbonate, and aluminum carbonate or hydroxide. Their relative phosphate-binding capacity has been assessed in human, in vivo studies that have measured phosphate recovery from stool and/or changes in urinary phosphate excretion or that have compared pairs of different binders where dose of binder in each group was titrated to a target level of serum phosphate. The relative phosphate-binding coefficient (RPBC) based on weight of each binder can be estimated relative to calcium carbonate, the latter being set to 1.0. A systematic review of these studies gave the following estimated RPBC: for elemental lanthanum, 2.0, for sevelamer hydrochloride or carbonate 0.75, for calcium acetate 1.0, for anhydrous magnesium carbonate 1.7, and for "heavy" or hydrated, magnesium carbonate 1.3. Estimated RPBC for aluminum-containing binders were 1.5 for aluminum hydroxide and 1.9 for aluminum carbonate. The phosphate-binding equivalent dose was then defined as the dose of each binder in g × its RPBC, which would be the binding ability of an equivalent weight of calcium carbonate. The phosphate-binding equivalent dose may be useful in comparing changes in phosphate binder prescription over time when multiple binders are being prescribed, when estimating an initial binder prescription, and also in phosphate kinetic modeling.

Cytochrome P450 3A5 expression in the kidneys of patients with calcineurin inhibitor nephrotoxicity.

BACKGROUND: Nephrotoxicity secondary to calcineurin inhibitors is common in renal transplant recipients, occurring in 76-94% of patients. The role of drug transporters (P-glycoprotein) and drug metabolizing enzymes (cytochrome P450) as predisposing factors toward nephrotoxicity or its prevention has not been thoroughly examined. METHODS: The objective of this study was to analyse cytochrome P450 3A5 (CYP3A5) expression in kidneys of solid organ recipients by immunohistochemistry to determine if there is an association between expression of this enzyme and calcineurin inhibitor toxicity. Transplant recipients were compared with a control group. RESULTS: Apical tubular plasma membrane staining for CYP3A5 was present in 62% of study and 100% of control biopsies (P=0.0012). Proximal and distal tubular nuclear staining intensity was similar between groups. Cytoplasmic staining in both the proximal (2.1+/-0.9 vs 1.4+/-0.9) and distal (2.8+/-0.5 vs 1.8+/-1.1) tubules was greater in the control vs study population specimens, respectively (P=0.0093 and P=0.0005, respectively). Regression models that controlled for use of CYP3A inhibiting and inducing medications, age, gender, race and glomerular filtration rate did not predict differences between study groups with regard to staining locations and intensity, except for the cytoplasm of the distal tubule, where intensity of staining was significantly lower in the study group (0.9+/-0.3; P=0.002). CONCLUSIONS: This study showed decreased expression of CYP3A5 in nephrotoxic biopsies as compared with a control group. Our data suggest that the relationship between reduced presence of CYP3A5 in the kidney tubules and nephrotoxicity should be further explored to elucidate the role of this enzyme in mediating toxicity.

The clinical and renal consequences of contrast-induced nephropathy.

Contrast-induced nephropathy (CIN), an impairment of renal function following intravascular injection of contrast media, is commonly defined as an increase in the baseline serum creatinine concentration of >25% or 0.5 mg/dl (44 micromol/l). The incidence of CIN does not appear to have changed appreciably in the last three decades, and it continues to be the third leading cause of hospital-acquired acute renal failure (ARF). In the general population, the incidence of CIN is estimated to be 1-2%. However, the risk for developing CIN may be as high as 50% in some high-risk patient subgroups, such as those with diabetes mellitus and pre-existing renal impairment. Patients who develop CIN after percutaneous coronary intervention sustain an increase in both short- and long-term mortality whether or not chronic kidney disease was present prior to contrast exposure. The diminished long-term survival in patients with CIN has been observed for both, those whose ARF is not severe enough to require dialysis as well as those requiring dialysis. Treatment is limited to supportive measures while awaiting the resolution of the renal impairment. At times, this does not occur. Because of the lack of treatment options and because CIN is associated with serious short- and long-term sequelae, emphasis needs to be directed at preventative measures, identification of high-risk patients and education of all physicians involved in the care of these patients in order to reduce the incidence of CIN.

Non-contrast-enhanced computerized tomography and analgesic-related kidney disease: report of the national analgesic nephropathy study.

Previous studies suggested that the non-contrast-enhanced computerized tomography (CT) scan is a highly reliable tool for the diagnosis of analgesic-associated renal disease. However, this issue has not been addressed in the US population. A total of 221 incident patients with ESRD from different regions of the United States underwent a helical CT scan and detailed questioning about drug history. Specific renal anatomic criteria were developed to determine whether a constellation of CT findings (small indented calcified kidneys [SICK]) is linked to analgesic ingestion. For approximating use before the onset of renal disease, only analgesic ingestion at least 9 yr before starting dialysis was considered relevant. Fifteen patients met the criteria for SICK. This represented 7% of the enrolled patients and approximately 1% of the total ESRD population. There was a significant increase in the estimated risk among patients with a history of heavy aspirin ingestion (odds ratio [OR] 7.4 [95% confidence interval (CI) 1.2 to 43] for > or =1 kg lifetime; OR 8.8 [95% CI 1.2 to 66] for > or =0.3 kg/yr). Total analgesic ingestion of > or =0.3 kg/yr also was significantly associated with SICK (OR 8.2; 95% CI 1.5 to 45). These findings were accounted for largely by combination products that contained aspirin and phenacetin (used by three patients with SICK), which are no longer available. In addition, the CT finding of SICK was present only in a minority of heavy analgesic users, yielding a sensitivity of 5 to 26%. Findings of SICK are infrequent in the US ESRD population and do not occur among a sufficient proportion of heavy analgesic users to render the non-contrast-enhanced CT scan a sensitive tool to detect analgesic-associated kidney injury.

Immunosuppression, hepatitis C infection, and acute renal failure in HIV-infected patients.

BACKGROUND: Low CD4 cell counts predict HIV-related morbidity and mortality and may be associated with acute renal failure (ARF). OBJECTIVE: To estimate the effect of CD4 cell count on the incidence rate (IR) of ARF in ambulatory HIV-infected patients with access to highly active antiretroviral therapy. METHODS: Observational clinical cohort of HIV-infected patients recruited from a university-based infectious diseases clinic, between 2000 and 2002, and followed up until December 31, 2002. Poisson log-linear regression models were used to calculate ARF IRs, IR differences, and IR ratios. RESULTS: The mean age of the 705 study participants was 40 years, two thirds were male, and 61% were African American. Incidence rates of ARF were higher at lower CD4 cell counts and among patients who were coinfected with hepatitis C. Patients with hepatitis C coinfection who also had low CD4 cell counts had the highest adjusted IR of ARF. CONCLUSION: Immunosuppression and hepatitis C virus coinfection are associated with increased IRs of ARF in ambulatory HIV-1-infected patients.

Calcineurin inhibitor-induced nephrotoxicity and renal expression of P-glycoprotein.

STUDY OBJECTIVE: To evaluate immunohistochemistry staining patterns for P-glycoprotein (P-gp) and a marker of early apoptosis (active caspase-3) in renal biopsy specimens obtained from solid organ transplant recipients with nephrotoxicity and those from a control group. DESIGN: Retrospective analysis of pathology specimens and medical records. SETTING: Medical university. SUBJECTS: Twenty-nine solid organ transplant recipients with nephrotoxicity and 32 control patients. MEASUREMENTS AND MAIN RESULTS: Medical records were reviewed for patient demographics, clinical laboratory results, and prescribed drugs. Immunohistochemistry techniques using primary antibodies to P-gp and active caspase-3 were performed to evaluate staining patterns of these proteins in the kidney specimens. Differences in measures of interest between groups were compared with the Fisher exact test for categoric data and Wilcoxon rank sum test for continuous data. Logistic and linear modeling were used to evaluate difference in measures of P-gp and active caspase-3 between groups while controlling for confounders. Immunohistochemistry confirmed the presence of P-gp in the renal tubules (apical and basal membranes and cytoplasm). Intensity of P-gp staining (score range 0-4) was reduced in renal specimens of transplant recipients with nephrotoxicity compared with the control specimens (mean +/- SD intensity scores 3.2 +/- 0.7 vs 3.8 +/- 0.4, p=0.0002). Neither P-gp-inducing nor P-gp-inhibiting drugs predicted expression of P-gp in the renal specimens of either group. The extent of tubular staining (score range 1-4) for the apoptosis marker, active caspase-3, was less in the nephrotoxicity group than in the control group (mean +/- SD extent scores 1.7 +/- 0.6 vs 2.8 +/- 0.5, p=0.0003). CONCLUSION: P-glycoprotein expression was less pronounced in renal biopsy specimens with calcineurin inhibitor-induced nephrotoxicity compared with the nonnephrotoxic control specimens. Reduced P-gp expression was evident even when the analysis controlled for factors such as renal function, age, sex, race, diabetes mellitus, level of proteinuria, or prescribed therapy with P-gp inducers or inhibitors. Interpretation of the results from active caspase-3 staining requires further study.

A long-term, open-label extension study on the safety of treatment with lanthanum carbonate, a new phosphate binder, in patients receiving hemodialysis.

BACKGROUND: Lanthanum carbonate, a new phosphate binder, is effective in reducing serum phosphorus levels in patients with end-stage renal disease. A 1-year extension study to two randomized controlled studies was conducted to evaluate the long-term safety of lanthanum carbonate in patients who received hemodialysis. RESEARCH DESIGN AND METHODS: Patients from two previous lanthanum carbonate studies were eligible to continue treatment in a 1-year open-label extension. A total of 77 patients (N = 77; 11 from Study 1, 66 from Study 2) were enrolled in this extension. The mean age of patients was 60.9 years (SD +/- 12.5 years); 65% were male and 35% were female. All patients received lanthanum carbonate at the optimal dose for phosphorus control, determined in their previous study. Safety and tolerability were assessed by monitoring adverse events, laboratory parameters, and vital signs. The number of patients who maintained serum phosphorus levels at < or = 5.9 mg/dL (1.9 mmol/L) was recorded, along with serum calcium, calcium x phosphorus product, and parathyroid hormone levels. RESULTS: Lanthanum carbonate was well tolerated and was associated with few treatment-related adverse events. The most commonly reported adverse events were nausea (26.0%), peripheral edema (23.4%), and myalgia (20.8%). No treatment-related serious adverse events occurred. By Week 4, the mean serum phosphorus level had decreased by approximately 1 mg/dL to 5.7 +/- 2.0 mg/dL (1.84 +/- 0.7 mmol/L). At the end of the study, the mean pre-dialysis serum phosphorus level was 5.7 +/- 1.4 mg/dL (1.84 +/- 0.5 mmol/L); 53% of patients had controlled phosphorus levels. Calcium x phosphorus product decreased during Week 1 and remained within a clinically acceptable range thereafter. There were no clinically significant changes in serum calcium, or parathyroid hormone levels. CONCLUSION: Lanthanum carbonate is well tolerated and is effective for the long-term maintenance of serum phosphorus control in patients with end-stage renal disease.

Incidence and etiology of acute renal failure among ambulatory HIV-infected patients.

BACKGROUND: Acute renal failure (ARF) is a cause of renal dysfunction in human immunodeficiency virus (HIV)-infected patients. Its incidence and causes have not been studied since the introduction of highly active antiretroviral therapy (HAART) in HIV ambulatory patients. METHODS: This is a prospective cohort study of 754 HIV patients, 18 years or older, seen at a university-based infectious disease clinic between 2000 and 2002. ARF was identified using proportional increases in serum creatinine from baseline and by chart review. Clinical conditions were assessed at the time of the ARF event. ARF incidence rates (IR) were calculated by dividing the number of events by person time at risk. To compare patients with and without ARF, t test or chi-square test were used. RESULTS: Patient's mean age was 40 years; 68% were male and 61% were black. One hundred-eleven ARF events occurred in 71 subjects (IR 5.9 per 100 person-years; 95% CI 4.9, 7.1). ARF was more common in men, in those with CD4 cell count <200 cells/mm(3), and HIV RNA levels >10,000 copies/mL. These patients more often had acquired immunodeficiency syndrome (AIDS), hepatitis C infection (HCV), and have received HAART. ARF was mainly community-acquired, due to prerenal causes or acute tubular necrosis, and associated with opportunistic infections and drugs. Liver disease was a cause of ARF in HCV-infected patients. CONCLUSION: ARF is common in ambulatory HIV patients. Immunosuppression, infection, and HCV are important conditions associated with ARF in the post-HAART era.

Phosphorus management in end-stage renal disease.

Chronic kidney disease is an important public health problem, with an increasing number of patients worldwide. One important outcome of renal failure is disordered mineral metabolism, most notably involving calcium and phosphorus balance. Of importance is that increased serum phosphorus levels are associated with increased mortality rates. Despite dietary restrictions, patients receiving dialysis invariably experience hyperphosphatemia and require treatment with phosphate binders. Existing phosphate binders are effective in reducing serum phosphorus levels, but are associated with a number of important disadvantages. Lanthanum carbonate, a new noncalcium, nonaluminum phosphate binder, represents a promising treatment for hyperphosphatemia.

N-acetylcysteine for the prevention of radiocontrast induced nephropathy: a meta-analysis of prospective controlled trials.

N-acetylcysteine has been recommended for patients with renal insufficiency who are to receive radiocontrast media. However, trials of oral N-acetylcysteine for the prevention of radiocontrast-induced nephropathy have yielded inconsistent results. A systematic review of patient and study characteristics was undertaken to discover possible explanations of the inconsistencies. The databases MEDLINE, EMBASE, and CENTRAL (1966 to March 2003) were searched in all languages, and conference proceedings from several professional societies from the years 1999 to 2003 were also searched. Only prospective controlled trials of oral N-acetylcysteine were included. Risk difference estimates and 95% confidence intervals were calculated. The estimates were examined for evidence of publication bias and heterogeneity. Stratified and meta-regression analyses were used to compare estimates by study and patient characteristics. Identified were 16 studies, 15 published and 1 unpublished. There was no evidence of publication bias, but there was substantial evidence of heterogeneity, thus precluding reliance on a meaningful summary effect estimate. Meta-regression identified several patient and study characteristics, with some evidence of association with study-specific estimates. None of these characteristics, however, formed subsets of studies with results that were homogeneous enough to aggregate. Research on N-acetylcysteine and the incidence of radiocontrast nephropathy is too inconsistent at present to warrant a conclusion on efficacy or a recommendation for its routine use. Identified patient and study characteristics may be responsible for some, but not all, of this inconsistency. A large, randomized, placebo-controlled trial, a pooled analysis of patient-level data, or both may resolve this issue.

Randomized, double-blind, placebo-controlled, dose-titration, phase III study assessing the efficacy and tolerability of lanthanum carbonate: a new phosphate binder for the treatment of hyperphosphatemia.

BACKGROUND: Lanthanum carbonate is a novel, non-calcium, non-aluminum phosphate binder under evaluation for the treatment of hyperphosphatemia in end-stage renal disease (ESRD) patients receiving either hemodialysis or continuous ambulatory peritoneal dialysis. METHODS: This 16-week study assessed the control of serum phosphorus with lanthanum carbonate, and its effects on serum calcium, calcium x phosphorus product, and parathyroid hormone (PTH). Hemodialysis patients > or =18 years old entered into a 1- to 3-week washout period during which serum phosphorus levels rose to >5.9 mg/dL (1.90 mmol/L). In total, 126 patients were titrated with lanthanum carbonate at doses containing 375, 750, 1,500, 2,250, or 3,000 mg/d elemental lanthanum, given in divided doses with meals over a 6-week period, to achieve serum levels < or =5.9 mg/dL. By the end of dose titration, 11/126 (9%) patients received < or =750 mg/d of lanthanum, 25 (20%) received 1,500 mg/d, 37 (29%) received 2,250 mg/d, and 53 (42%) received 3,000 mg/d. Following titration, patients were randomized to receive either lanthanum carbonate or placebo during a 4-week, double-blind maintenance phase. RESULTS: At the study endpoint, the mean difference in serum phosphorus between the lanthanum carbonate and placebo treatment arms was 1.91 mg/dL (0.62 mmol/L) (P < 0.0001). Calcium x phosphorus product (P < 0.0001) and serum PTH levels (P < 0.01) were also significantly lower with lanthanum carbonate versus placebo. The incidence of drug-related adverse events was similar between placebo- and lanthanum carbonate-treated patients. CONCLUSION: Lanthanum carbonate is an effective and well-tolerated agent for the treatment of hyperphosphatemia in patients with ESRD.

Protective effect of glycine on renal injury induced by ischemia-reperfusion in vivo.

Although glycine prevents renal tubular cell injury in vitro, its effect in vivo is not clear. The purpose of this study was to investigate whether a bolus injection of glycine given before reperfusion plus continuous dietary supplementation afterward would reduce renal injury caused by ischemia-reperfusion. Female Sprague-Dawley rats received a semisynthetic powdered diet containing 5% glycine and 15% casein (glycine group) or 20% casein (control group). Two days later, renal ischemia was produced by cross-clamping the left renal vessels for 15 min, followed by reperfusion. The right kidney was removed before reperfusion. The postischemic glomerular filtration rate (GFR) showed that renal function was less impaired and recovered more quickly in rats receiving glycine. For example, at day 7, GFR in controls (0.31 +/- 0.03 ml x min(-1) x 100 g(-1)) was about one-half that of glycine-treated rats (0.61 +/- 0.06 ml x min(-1) x 100 g(-1), P < 0.05). Furthermore, tubular injury and cast formation observed in controls was minimized by glycine (pathology score, 3.2 +/- 0.4 vs. 1.0 +/- 0.4, P < 0.05). Urinary lactate dehydrogenase (LDH) concentration was elevated by ischemia-reperfusion in the control group (260 +/- 22 U/l), but values were significantly lower by about fourfold (60 +/- 30 U/l) in glycine-fed rats. Similarly, free radical production in urine was significantly lower in glycine-treated animals. Importantly, on postischemic day 1, binding of pimonidazole, an in vivo hypoxia marker, was increased in the outer medulla in controls; however, this phenomenon was prevented by glycine. Two weeks later, mild leukocyte infiltration and interstitial fibrosis were still observed in controls, but not in kidneys from glycine-treated rats. In conclusion, these results indicate that administration of glycine indeed reduces mild ischemia-reperfusion injury in the kidney in vivo, in part by decreasing initial damage and preventing chronic hypoxia.