Acute Renal Effects of Intravenous Bisphosphonates in the Rat

A review of renal tubular acidosis

OBJECTIVE

To review the current scientific literature on renal tubular acidosis (RTA) in people and small animals, focusing on diseases in veterinary medicine that result in secondary RTA.

DATA SOURCES

Scientific reviews and original research publications on people and small animals focusing on RTA.

SUMMARY

RTA is characterized by defective renal acid-base regulation that results in normal anion gap hyperchloremic metabolic acidosis. Renal acid-base regulation includes the reabsorption and regeneration of bicarbonate in the renal proximal tubule and collecting ducts and the process of ammoniagenesis. RTA occurs as a primary genetic disorder or secondary to disease conditions. Based on pathophysiology, RTA is classified as distal or type 1 RTA, proximal or type 2 RTA, type 3 RTA or carbonic anhydrase II mutation, and type 4 or hyperkalemic RTA. Fanconi syndrome comprises proximal RTA with additional defects in proximal tubular function. Extensive research elucidating the genetic basis of RTA in people exists. RTA is a genetic disorder in the Basenji breed of dogs, where the mutation is known. Secondary RTA in human and veterinary medicine is the sequela of diseases that include immune-mediated, toxic, and infectious causes. Diagnosis and characterization of RTA include the measurement of urine pH and the evaluation of renal handling of substances that should affect acid or bicarbonate excretion.

CONCLUSIONS

Commonality exists between human and veterinary medicine among the types of RTA. Many genetic defects causing primary RTA are identified in people, but those in companion animals other than in the Basenji are unknown. Critically ill veterinary patients are often admitted to the ICU for diseases associated with secondary RTA, or they may develop RTA while hospitalized. Recognition and treatment of RTA may reverse tubular dysfunction and promote recovery by correcting metabolic acidosis.

Zoledronic Acid-Associated Fanconi Syndrome in Patients With Cancer

Zoledronic acid (ZA) is an antiresorptive agent typically used for fracture prevention in postmenopausal osteoporosis, malignancy-associated metastatic bone lesions, and as a treatment for hypercalcemia. ZA is excreted almost entirely by the kidney; as a result, a reduction in renal clearance can lead to its accumulation and potential renal toxicity. Although uncommon, acute kidney injury (AKI) from intravenous bisphosphonates has been described, with different patterns including tubulointerstitial nephritis, acute tubular necrosis, as well as focal segmental glomerulosclerosis. Here we present 4 patients with an underlying malignancy who each developed evidence of generalized proximal tubular dysfunction, also known as Fanconi syndrome, approximately 1 week after receiving treatment with ZA. On presentation, all patients had AKI, low serum bicarbonate levels, abnormal urinary acidification, hypophosphatemia, hypokalemia, and increased urine amino acid excretion or renal glycosuria. Based on the temporal association between ZA infusion and the development of these electrolyte abnormalities, each case is highly suggestive of ZA-associated Fanconi syndrome. Due to the severity of presentation, all required discontinuation of ZA and ongoing electrolyte repletion. Nephrologists and oncologists should be aware of this complication and consider ZA as a possible trigger of new-onset Fanconi syndrome.

Bisphosphonates to reduce bone fractures in stage 3B+ chronic kidney disease: a propensity score-matched cohort study

BACKGROUND

Bisphosphonates are contraindicated in patients with stage 4+ chronic kidney disease. However, they are widely used to prevent fragility fractures in stage 3 chronic kidney disease, despite a lack of good-quality data on their effects.

OBJECTIVES

The aims of each work package were as follows. Work package 1: to study the relationship between bisphosphonate use and chronic kidney disease progression. Work package 2: to study the association between using bisphosphonates and fracture risk. Work package 3: to determine the risks of hypocalcaemia, hypophosphataemia, acute kidney injury and upper gastrointestinal events associated with using bisphosphonates. Work package 4: to investigate the association between using bisphosphonates and changes in bone mineral density over time.

DESIGN

This was a new-user cohort study design with propensity score matching.

SETTING AND DATA SOURCES

Data were obtained from UK NHS primary care (Clinical Practice Research Datalink GOLD database) and linked hospital inpatient records (Hospital Episode Statistics) for work packages 1-3 and from the Danish Odense University Hospital Databases for work package 4.

PARTICIPANTS

Patients registered in the data sources who had at least one measurement of estimated glomerular filtration rate of < 45 ml/minute/1.73 m2 were eligible. A second estimated glomerular filtration rate value of < 45 ml/minute/1.73 m2 within 1 year after the first was requested for work packages 1 and 3. Patients with no Hospital Episode Statistics linkage were excluded from work packages 1-3. Patients with < 1 year of run-in data before index estimated glomerular filtration rate and previous users of anti-osteoporosis medications were excluded from work packages 1-4.

INTERVENTIONS/EXPOSURE

Bisphosphonate use, identified from primary care prescriptions (for work packages 1-3) or pharmacy dispensations (for work package 4), was the main exposure.

MAIN OUTCOME MEASURES

Work package 1: chronic kidney disease progression, defined as stage worsening or starting renal replacement. Work package 2: hip fracture. Work package 3: acute kidney injury, hypocalcaemia and hypophosphataemia identified from Hospital Episode Statistics, and gastrointestinal events identified from Clinical Practice Research Datalink or Hospital Episode Statistics. Work package 4: annualised femoral neck bone mineral density percentage change.

RESULTS

Bisphosphonate use was associated with an excess risk of chronic kidney disease progression (subdistribution hazard ratio 1.12, 95% confidence interval 1.02 to 1.24) in work package 1, but did not increase the probability of other safety outcomes in work package 3. The results from work package 2 suggested that bisphosphonate use increased fracture risk (hazard ratio 1.25, 95% confidence interval 1.13 to 1.39) for hip fractures, but sensitivity analyses suggested that this was related to unresolved confounding. Conversely, work package 4 suggested that bisphosphonates improved bone mineral density, with an average 2.65% (95% confidence interval 1.32% to 3.99%) greater gain in femoral neck bone mineral density per year in bisphosphonate users than in matched non-users.

LIMITATIONS

Confounding by indication was a concern for the clinical effectiveness (i.e. work package 2) data. Bias analyses suggested that these findings were due to inappropriate adjustment for pre-treatment risk. work packages 3 and 4 were based on small numbers of events and participants, respectively.

CONCLUSIONS

Bisphosphonates were associated with a 12% excess risk of chronic kidney disease progression in participants with stage 3B+ chronic kidney disease. No other safety concerns were identified. Bisphosphonate therapy increased bone mineral density, but the research team failed to demonstrate antifracture effectiveness.

FUTURE WORK

Randomised controlled trial data are needed to demonstrate antifracture efficacy in patients with stage 3B+ chronic kidney disease. More safety analyses are needed to characterise the renal toxicity of bisphosphonates in stage 3A chronic kidney disease, possibly using observational data.

STUDY REGISTRATION

This study is registered as EUPAS10029.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 25, No. 17. See the NIHR Journals Library website for further project information. The project was also supported by the National Institute for Health Research Biomedical Research Centre, Oxford.

Evaluation of the inverse electron demand Diels-Alder reaction in rats using a scandium-44-labelled tetrazine for pretargeted PET imaging

BACKGROUND

Pretargeted imaging allows the use of short-lived radionuclides when imaging the accumulation of slow clearing targeting agents such as antibodies. The biotin-(strept)avidin and the bispecific antibody-hapten interactions have been applied in clinical pretargeting studies; unfortunately, these systems led to immunogenic responses in patients. The inverse electron demand Diels-Alder (IEDDA) reaction between a radiolabelled tetrazine (Tz) and a trans-cyclooctene (TCO)-functionalized targeting vector is a promising alternative for clinical pretargeted imaging due to its fast reaction kinetics. This strategy was first applied in nuclear medicine using an ¹¹¹In-labelled Tz to image TCO-functionalized antibodies in tumour-bearing mice. Since then, the IEDDA has been used extensively in pretargeted nuclear imaging and radiotherapy; however, these studies have only been performed in mice. Herein, we report the ⁴⁴Sc labelling of a Tz and evaluate it in pretargeted imaging in Wistar rats.

RESULTS

⁴⁴Sc was obtained from an in house ⁴⁴Ti/⁴⁴Sc generator. A 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-functionalized tetrazine was radiolabelled with ⁴⁴Sc resulting in radiochemical yields of 85-95%, a radiochemical purity > 99% at an apparent molar activity of 1 GBq/mmol. The ⁴⁴Sc-labelled Tz maintained stability in solution for up to 24 h. A TCO-functionalized bisphosphonate, which accumulates in skeletal tissue, was used as a targeting vector to evaluate the ⁴⁴Sc-labelled Tz. Biodistribution data of the ⁴⁴Sc-labelled Tz showed specific uptake (0.9 ± 0.3% ID/g) in the bones (humerus and femur) of rats pre-treated with the TCO-functionalized bisphosphonate. This uptake was not present in rats not receiving pre-treatment (< 0.03% ID/g).

CONCLUSIONS

We have prepared a ⁴⁴Sc-labelled Tz and used it in pretargeted PET imaging with rats treated with TCO-functionalized bisphosponates. This allowed for the evaluation of the IEDDA reaction in animals larger than a typical mouse. Non-target accumulation was low, and there was a 30-fold higher bone uptake in the pre-treated rats compared to the non-treated controls. Given its convenient half-life and the ability to perform positron emission tomography with a previously studied DOTA-functionalized Tz, scandium-44 (t_1/2 = 3.97 h) proved to be a suitable radioisotope for this study.

Risedronate Attenuates Podocyte Injury in Phosphate Transporter-Overexpressing Rats

Osteoporosis patients with chronic kidney disease (CKD) are becoming common in our superaging society. Renal dysfunction causes phosphorus accumulation in the circulating plasma and leads to the development of CKD-mineral bone disorder (MBD). We have previously reported that type III Pi transporter-overexpressing transgenic (Pit-1 TG) rats manifest phosphate (Pi)-dependent podocyte injury. In the present study, we explored the effect of risedronate on Pi-induced podocyte injury in vivo. Pit-1 TG rats and wild-type rats at 5 weeks old were divided into a risedronate-treated group and an untreated group. We subcutaneously administered 5 μg/kg body weight of risedronate or saline twice a week during the experimental period. Risedronate did not alter serum creatinine levels at 5, 8, and 12 weeks of age. However, electron microscopy images showed that thickening of the glomerular basement membrane was improved in the risedronate treatment group. Furthermore, immunostaining for podocyte injury markers revealed that both desmin- and connexin43-positive areas were smaller in the risedronate-treated group than in the untreated group, suggesting that bisphosphonates could rescue Pi-induced podocyte injury. In conclusion, our findings suggest that risedronate could maintain glomerular barrier function by rescuing Pi-induced podocyte injury.

Skeletal accumulation of fluorescently tagged zoledronate is higher in animals with early stage chronic kidney disease

This work examines the skeletal accumulation of fluorescently tagged zoledronate in an animal model of chronic kidney disease. The results show higher accumulation in 24-h post-dose animals with lower kidney function due to greater amounts of binding at individual surfaces.

INTRODUCTION

Chronic kidney disease (CKD) patients suffer from increased rates of skeletal-related mortality from changes driven by biochemical abnormalities. Bisphosphonates are commonly used in reducing fracture risk in a variety of diseases, yet their use is not recommended in advanced stages of CKD. This study aimed to characterize the accumulation of a single dose of fluorescently tagged zoledronate (FAM-ZOL) in the setting of reduced kidney function.

METHODS

At 25 weeks of age, FAM-ZOL was administered to normal and CKD rats. Twenty-four hours later, multiple bones were collected and assessed using bulk fluorescence imaging, two-photon imaging, and dynamic histomorphometry.

RESULTS

CKD animals had significantly higher levels of FAM-ZOL accumulation in the proximal tibia, radius, and ulna, but not in lumbar vertebral body or mandible, based on multiple measurement modalities. Although a majority of trabecular bone surfaces were covered with FAM-ZOL in both normal and CKD animals, the latter had significantly higher levels of fluorescence per unit bone surface in the proximal tibia.

CONCLUSIONS

These results provide new data regarding how reduced kidney function affects drug accumulation in rat bone.

The role of vitamin E in the prevention of zoledronic acid-induced nephrotoxicity in rats: a light and electron microscopy study

INTRODUCTION

Bisphosphonates are widely used in metastatic cancer such as prostate and breast cancer, and their nephrotoxic effects have been established previously. In this study we aimed to evaluate both the nephrotoxic effects of zoledronic acid (ZA) and the protective effects of vitamin E (Vit-E) on this process under light and electron microscopy.

MATERIAL AND METHODS

A total of 30 male Sprague-Dawley rats were divided into 3 groups. The first group constituted the control group. The second group was given i.v. ZA of 3 mg/kg once every 3 weeks for 12 weeks from the tail vein. The third group received the same dosage of ZA with an additional i.m. injection of 15 mg Vit-E every week for 12 weeks. Tissues were taken 4 days after the last dose of ZA for histopathological and ultrastructural evaluation. Paller score, tubular epithelial thickness and basal membrane thickness were calculated for each group.

RESULTS

For group 2, the p-values are all < 0.001 for Paller score, epitelial thickness, and basal membrane thickness. For group 3 (ZA + Vit. E), the p-values are < 0.001 for Paller score, 0.996 for epitelial thickness, and < 0.001 basal membrane thickness. Significant differences were also observed in ultrastructural changes for group 2. However, adding Vit-E to ZA administration reversed all the histopathological changes to some degree, with statistical significance.

CONCLUSIONS

Administration of ZA had nephrotoxic effects on rat kidney observed under both light and electron microscopy. Concomitant administration of Vit-E significantly reduces toxic histopathological effects of ZA.

What Animal Models Have Taught Us About the Safety and Efficacy of Bisphosphonates in Chronic Kidney Disease

PURPOSE OF REVIEW

Bisphosphonates (BPs) have long been the gold-standard anti-remodeling treatment for numerous metabolic bone diseases. Since these drugs are excreted unmetabolized through the kidney, they are not recommended for individuals with compromised kidney function due to concerns of kidney and bone toxicity. The goal of this paper is to summarize the preclinical BP work in models of kidney disease with particular focus on the bone, kidney, and vasculature.

RECENT FINDINGS

Summative data exists showing positive effects on bone and vascular calcifications with minimal evidence for bone or kidney toxicity in animal models. Preclinical data suggest it may be worthwhile to take a step back and reconsider the use of bisphosphonates to lessen skeletal/vascular complications associated with compromised kidney function.

Mechanism of Action, Pharmacokinetic and Pharmacodynamic Profile, and Clinical Applications of Nitrogen-containing Bisphosphonates

Nitrogen-containing bisphosphonates (nBPs) are bone-specific agents that inhibit farnesyl diphosphate synthase. nBPs’ strong affinity for bone, and not for other tissues, makes them potent inhibitors of bone resorption and bone remodeling activity, with limited potential for side-effects in non-skeletal tissues. Five nBPs are currently approved in the United States. The primary indications are for treatment of osteoporosis (alendronate, ibandronate, and risedronate) and treatment/prevention of skeletal-related events (SREs) in multiple myeloma and breast and prostate cancer patients (ibandronate, pamidronate, and zoledronic acid). nBPs are the most efficacious drugs available for these diseases, reducing osteoporotic fracture risk by 50–60% in persons with low bone mass or prior osteoporotic fracture, and SREs by one-third in cancer patients. The absorbed nBP dose for cancer patients is from seven to ten times that in osteoporosis patients. nBPs are unique in that they first exert profound pharmacodynamic effects long after their blood levels reach zero. Current pharmacokinetic studies indicate that approximately half of any nBP dose reaches the skeleton, with an early half-life of ten days, and a terminal half-life of about ten years. Practical study design limitations and theoretical considerations suggest that both the half-life and the amount of nBP retained in the skeletons of patients on long-term nBP therapy are substantially overestimated by extrapolation directly from current pharmacokinetic data. In fact, the amount of nBP being released from skeletal tissues of long-term-treated patients, particularly in osteoporosis patients, becomes insufficient to maintain full pharmacodynamic efficacy relatively soon after dosing is interrupted.

Documentation of renal glomerular and tubular impairment and glomerular hyperfiltration in multitransfused patients with beta thalassemia

Urinary albumin to creatinine (ACR) and beta2 microglobulin to creatinine ratios (BCR) are the surrogate and robust markers of renal glomerulopathy and tubulopathy, respectively. These markers predict short-term renal deterioration and mortality in various conditions. We aimed to assess the frequency and predictors of glomerular and tubular defects, renal impairment, and hyperfiltration in 96 adult patients with beta thalassemia intermedia and major. ACR > 300 mg/g creatinine and BCR > 300 μg/g creatinine were used to define the renal glomerular and tubular damages, respectively. Glomerular filtration rate (eGFRcreat) was estimated according to 2009 the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Decreased eGFRcreat was defined as less than 60 mL/min per 1.73 m(2). Renal glomerular and/or tubular defects were observed in about 68.8 % of all patients. Forty percent of patients had glomerular hyperfiltration. None of the patients had a decreased eGFRcreat. T2* value ≤20 msec on cardiac magnetic resonance (cMR) was the only independent predictor of glomerular damage (p = 0.013). Use of alendronate was associated with less renal tubular damage (p = 0.007). Female gender and previous history of splenectomy were the independent predictors of glomerular hyperfiltration in multivariate analysis (p < 0.001 and p = 0.040, respectively). Renal tubular and glomerular damage is frequent in adult patients with thalassemia intermedia and major. T2* value on cMR was the only independent predictor of glomerular damage. However, since we did not explore all the parameters of iron, it is not possible to draw a definite conclusion about the association of cMR and glomerular damage. There is no association with cardiac iron overload/accumulation and tubular damage or hyperfiltration.

Inhibitory actions by ibandronate sodium, a nitrogen-containing bisphosphonate, on calcium-activated potassium channels in Madin-Darby canine kidney cells

The nitrogen-containing bisphosphonates used for management of the patients with osteoporosis were reported to influence the function of renal tubular cells. However, how nitrogen-containing bisphosphates exert any effects on ion currents remains controversial. The effects of ibandronate (Iban), a nitrogen-containing bisphosphonate, on ionic channels, including two types of Ca²⁺-activated K⁺ (K_Ca) channels, namely, large-conductance K_Ca (BK_Ca) and intermediate-conductance K_Ca (IK_Ca) channels, were investigated in Madin–Darby canine kidney (MDCK) cells. In whole-cell current recordings, Iban suppressed the amplitude of voltage-gated K⁺ current elicited by long ramp pulse. Addition of Iban caused a reduction of BK_Ca channels accompanied by a right shift in the activation curve of BK_Ca channels, despite no change in single-channel conductance. Ca²⁺ sensitivity of these channels was modified in the presence of this compound; however, the magnitude of Iban-mediated decrease in BK_Ca-channel activity under membrane stretch with different negative pressure remained unchanged. Iban suppressed the probability of BK_Ca-channel openings linked primarily to a shortening in the slow component of mean open time in these channels. The dissociation constant needed for Iban-mediated suppression of mean open time in MDCK cells was 12.2 μM. Additionally, cell exposure to Iban suppressed the activity of IK_Ca channels, and DC-EBIO or 9-phenanthrol effectively reversed its suppression. Under current-clamp configuration, Iban depolarized the cells and DC-EBIO or PF573228 reversed its depolarizing effect. Taken together, the inhibitory action of Iban on K_Ca-channel activity may contribute to the underlying mechanism of pharmacological or toxicological actions of Iban and its structurally similar bisphosphonates on renal tubular cells occurring in vivo.

Effect of different doses of zoledronic acid in establishing of bisphosphonate-related osteonecrosis

OBJECTIVES

To establish osteonecrosis of the jaws in rats treated with different doses of zoledronic acid (ZA).

METHODS

Male Wistar rats (n=6-7) received three consecutive weekly intravenous ZA infusions at doses of 0.04, 0.20 or 1.00mg/kg ZA or saline (control). Four weeks after the last administration, the animals were submitted to simple extraction of the lower left first molar. An additional dose of ZA was administered seven days later, and the animals were sacrificed 28 days after exodontia. Weight was measured and blood was collected weekly for analysis. The jaw was radiographically and microscopically examined along with the liver, spleen, kidney and stomach.

RESULTS

All ZA doses showed a higher radiolucent area than the control (p<0.0001), but the dose of 0.04mg/kg did not show BRONJ. Doses of 0.20 and 1.00mg/kg ZA showed histological evidence of bone necrosis (p=0.0004). Anaemia (p<0.0001, r(2)=0.8073) and leucocytosis (p<0.0001, r(2)=0.9699) are seen with an increase of lymphocytes (p<0.0001, r(2)=0.6431) and neutrophils and monocytes (p=0.0218, r(2)=0.8724) in all the animals treated with an increasing dose of ZA. Haemorrhage and ectasia were observed in the spleen (p=0.0004) and stomach (p=0.0168) in a dose-dependent manner, and the animals treated with ZA showed a lower rate of weight gain (p<0.0001).

CONCLUSIONS

We designed a bisphosphonate-related osteonecrosis of the jaw model that reproduces radiographic and histological parameters and mimics clinical alterations such as leucocytosis, anaemia and idiosyncratic inflammatory post infusion reactions.

Bisphophonates in CKD patients with low bone mineral density

Patients with chronic kidney disease-mineral and bone disorder (CKD-MBD) have a high risk of bone fracture because of low bone mineral density and poor bone quality. Osteoporosis also features low bone mass, disarranged microarchitecture, and skeletal fragility, and differentiating between osteoporosis and CKD-MBD in low bone mineral density is a challenge and usually achieved by bone biopsy. Bisphosphonates can be safe and beneficial for patients with a glomerular filtration rate of 30 mL/min or higher, but prescribing bisphosphonates in advanced CKD requires caution because of the increased possibility of low bone turnover disorders such as osteomalacia, mixed uremic osteodystrophy, and adynamic bone, even aggravating hyperparathyroidism. Therefore, bone biopsy in advanced CKD is an important consideration before prescribing bisphosphonates. Treatment also may induce hypocalcemia in CKD patients with secondary hyperparathyroidism, but vitamin D supplementation may ameliorate this effect. Bisphosphonate treatment can improve both bone mineral density and vascular calcification, but the latter becomes more unlikely in patients with stage 3-4 CKD with vascular calcification but no decreased bone mineral density. Using bisphosphonates requires considerable caution in advanced CKD, and the lack of adequate clinical investigation necessitates more studies regarding its effects on these patients.

Proliferative and nonproliferative lesions of the rat and mouse urinary system

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in the urinary tract of rats and mice. The standardized nomenclature of urinary tract lesions presented in this document is also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous developmental and aging lesions as well as those induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for urinary tract lesions in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Renal safety of ibandronate 6 mg infused over 15 min versus 60 min in breast cancer patients with bone metastases: a randomized open-label equivalence trial

PURPOSE

The aim of this study was to demonstrate the renal safety equivalence of ibandronate 6 mg infused over 15 min versus 60 min, in patients with bone metastases of breast cancer.

PATIENTS AND METHODS

Patients were females having breast cancer with at least one bone metastasis. Exclusion criteria were renal failure (creatinine clearance < 30 mL/min), tooth/jaw disorder or uncontrolled severe disease. Eligible patients were randomly assigned to receive nine ibandronate 6 mg i.v. infusions over either 15 min or 60 min. The primary outcome was the 95% confidence interval (CI) of the difference in creatinine clearance between groups, 28 days after the last infusion. The equivalence margin was ±8 mL/min.

RESULTS

Overall 334 patients were randomized (165-15 min infusions vs. 169 to 60 min infusions, 325 (159 vs. 166) were analyzed by intent-to-treat, and 312 (151 vs. 161) were analyzed per protocol. Per protocol, the 15 min-60 min difference in creatinine clearance [95% CI] was -3.00 [-8.18, 2.18]. By intent-to-treat, this difference was-2.91 [-7.99, 2.16]. Death and serious adverse event rates did not differ between groups. Three serious adverse events were considered related to ibandronate: an osteonecrosis of the jaw (15-min group), a pain in jaw and an enamel cracking (60-min group). Two renal failures, reported in the 60 min group, were not considered related to ibandronate. None occurred in the 15 min group.

CONCLUSION

Ibandronate may be infused over 15 min without clinically significant consequence on renal safety.

A case of acquired Fanconi syndrome induced by zoledronic acid

A 61-year-old woman with metastatic breast cancer was diagnosed as having acquired Fanconi syndrome. In this case, the cause of this syndrome was most likely zoledronic acid (Zometa), which had been infused intravenously at a dose of 4 mg over 15 minutes weekly because of malignancy-associated hypercalcemia. Zoledronic acid is nephrotoxic and may induce severe tubular dysfunction, which can cause development of Fanconi syndrome. Therefore, close monitoring of proximal tubular function is recommended during therapy with zoledronic acid, especially when frequent administration of zoledronic acid is needed.

Management of osteoporosis in CKD Stages 3 to 5

Osteoporosis and chronic kidney disease (CKD) are both common conditions of older adults and both may be associated with substantial morbidity. However, biochemical and histologic changes that occur with progressive kidney disease require specific interventions, some of which may be concordant with osteoporosis management in the general population, whereas others may be less relevant or perhaps even harmful. In this article, we review the diagnosis of and management strategies for osteoporosis in individuals with CKD, placing these into perspective with the recently published KDIGO (Kidney Disease: Improving Global Outcomes) guidelines for treatment of CKD-mineral and bone disorder (CKD-MBD). Specifically, we highlight osteoporosis treatment recommendations by CKD stage and discuss new avenues for osteoporosis treatment that may be useful in individuals with CKD.

The Effect of Alendronate, Risedronate, and Raloxifene on Renal Functions, Based on the Cockcroft and Gault Method, in Postmenopausal Women

BACKGROUND

Oral alendronate, risedronate, and raloxifene are effective treatment options in the management of postmenopausal osteoporosis. There is little previously reported about the renal safety profiles of these three agents in osteoporosis. We aimed to assess the risk of renal toxicity associated with oral alendronate, risedronate, and raloxifene in the treatment of osteoporosis, prospectively.

METHODS

One hundred and twenty-seven patients with osteoporosis and osteopenia according to lumbar or femoral-neck bone mineral density t score were enrolled in the study. The patients were randomized to alendronate 70 mg once weekly (n = 47), risedronate 35 mg once weekly (n = 44), or raloxifene 60 mg per day (n = 36) for one year. Preliminary screening included medical history, physical examination, lumbar and femoral bone mineral densitometry measurement, and blood biochemical tests, including renal function tests. The biochemical markers were then assessed at the end of 12 months.

RESULTS

There was no significant difference between basal and final renal function parameters of each group. Also these parameters did not differ between the three groups after 12 months of treatment period.

CONCLUSIONS

These results demonstrate that alendronate, risedronate, and raloxifene are all safe drugs for renal functions in the treatment of osteoporosis.

Risk of renal impairment after treatment with ibandronate versus zoledronic acid: a retrospective medical records review

PURPOSE

This retrospective study compared renal impairment rates in breast cancer, multiple myeloma, prostate cancer and non-small cell lung cancer patients treated with ibandronate or zoledronic acid.

STUDY DESIGN

Medical records in two German oncology clinics from May 2001 to March 2006 were retrospectively reviewed. Creatinine measurements were analyzed from baseline (before bisphosphonate treatment) to last available measurement for each patient. The Cox proportional hazards model and the Andersen-Gill extension of the Cox model for multiple events analysis were used for multivariate analysis, which controlled for age, clinic site, primary cancer type, baseline SCr or GFR value, prior bisphosphonate use, concomitant use of drugs associated with acute renal failure, and renal-related comorbidities.

RESULTS

Of 333 patients, 109 received ibandronate and 256 received zoledronic acid (32 patients had both drugs). Compared with ibandronate, the zoledronic acid group had a significantly better baseline renal function and fewer patients had a history of renal disease. Zoledronic acid treatment increased the relative risk (RR) and the incidence rate (IR) of renal impairment by approximately 1.5-fold in all assessed patients (all tumors) compared with ibandronate. Multivariate analysis found significantly higher hazards ratios for zoledronic acid over ibandronate (two to sixfold), after adjusting for differences in characteristics between the two treatment groups.

CONCLUSIONS

In this retrospective review, patients were significantly more likely to experience renal impairment with zoledronic acid than with ibandronate.

Bisphosphonates in chronic kidney disease; balancing potential benefits and adverse effects on bone and soft tissue

Cardiovascular disease is highly prevalent in chronic kidney disease (CKD) and is often associated with increased vascular stiffness and calcification. Recent studies have suggested a complex interaction between vascular calcification and abnormalities of bone and mineral metabolism, with an inverse relationship between arterial calcification and bone mineral density (BMD). Although osteoporosis is recognized and treated in CKD 1 to 3, the interpretation of BMD levels in the osteoporotic range is controversial in CKD 4, 5, and 5D when renal osteodystrophy is generally present. In addition, there is a paucity of data for patients with CKD mineral and bone disorder (MBD), because studies using bisphosphonates in postmenopausal and glucocorticoid-induced osteoporosis have generally excluded patients with significant CKD. For these patients, treatment of low BMD using standard therapies for osteoporosis is not without potential for harm due to the possibility of worsening low bone turnover, osteomalacia, mixed uraemic osteodystrophy, and of exacerbated hyperparathyroidism; and bisphosphonates should only be used selectively and with caution. Some experimental and clinical studies have also suggested that bisphosphonates may reduce progression of extra-osseous calcification and inhibit the development of atherosclerosis. The authors review the potential benefits and risks associated with bisphosphonate use for bone protection in CKD, and assess their effect on vascular calcification and atherosclerosis.

Bisphosphonate nephrotoxicity

Bisphosphonates are valuable agents for the treatment of post-menopausal osteoporosis (PMO), hypercalcemia of malignancy, and osteolytic bone metastases. Oral bisphosphonates are used mainly to treat PMO and are not associated with significant nephrotoxicity. In contrast, nephrotoxicity is a significant potential limiting factor to the use of intravenous (IV) bisphosphonates, and the nephrotoxicity is both dose-dependent and infusion time-dependent. The two main IV bisphosphonates available to treat hypercalcemia of malignancy and osteolytic bone disease in the United States are zoledronate and pamidronate. Patterns of nephrotoxicity described with these agents include toxic acute tubular necrosis and collapsing focal segmental glomerulosclerosis, respectively. With both of these agents, severe nephrotoxicity can be largely avoided by stringent adherence to guidelines for monitoring serum creatinine prior to each treatment, temporarily withholding therapy in the setting of renal insufficiency, and adjusting doses in patients with pre-existing chronic kidney disease. In patients with PMO, zoledronate and pamidronate are associated with significantly less nephrotoxicity, which undoubtedly relates to the lower doses and longer dosing intervals employed for this indication. Ibandronate is approved in the US for treatment of PMO and in Europe for treatment of PMO and malignancy-associated bone disease. Available data suggest that ibandronate has a safe renal profile without evidence of nephrotoxicity, even in patients with abnormal baseline kidney function.

Renal safety of intravenous bisphosphonates in the treatment of osteoporosis

Oral bisphosphonates are the mainstay of treatment for osteoporosis but cannot be used in some patients due to gastrointestinal contraindications, gastrointestinal intolerance, malabsorption or the inability to comply with dosing requirements. In such patients, intravenous bisphosphonates are a useful alternative. This review summarises the renal safety issues associated with the use of intravenous bisphosphonates for osteoporosis. Intravenous bisphosphonates are generally well tolerated, which may be a reflection of their selective activity in bone and metabolic stability. Adverse effects on renal function are primarily related to infusion rate and dose. Due to lack of data, no conclusions can be made regarding bisphosphonate safety in patients with intrinsic renal disease or an estimated glomerular filtration rate of < 30 ml/min.

Is there a role for bisphosphonates in chronic kidney disease?

Patients with stage 5 chronic kidney disease (CKD) including those on dialysis can and do develop osteoporosis. They also develop a wide range of other metabolic bone diseases that may look like osteoporosis when it is defined by either the World Health Organization bone mineral density (BMD) criteria or by the development of fragility fractures. Those dialysis patients with osteoporosis that is due to gonadal hormone deficiency such as postmenopausal osteoporosis, glucocorticoid-induced osteoporosis, or male osteoporosis may benefit from the administration of bisphosphonates (BPs). The challenges lie in the diagnosis of osteoporosis in this population where adynamic, osteomalacic, hyperparathyroid, or aluminum bone disease are also prevalent, with concommitant low BMD and low trauma fractures, but where BPs may be contraindicated. The only secure means to diagnose osteoporosis in this patient population is by quantitative bone histomorphometry demonstrating low trabecular bone volume and disrupted microarchitecture. Once the diagnosis of osteoporosis is established, BPs should be considered for a well-defined brief period of time (e.g., 2-3 years), even though there is no evidence for a fracture reduction benefit in this population. If a BP is chosen there may be a need for dose adjustment or slower infusion rates (for the intravenous formulations), as a greater bone retention may occur for these renally cleared agents. While it is unknown what consequences could develop from increased bone retention in patients with little renal function, data are needed if more bone retention of BP might lead to a greater risk of the development of adynamic bone disease and lower bone strength. More data are needed to define the risks and benefits of BPs in patients with stage 5 CKD.

Differences in Nephrotoxicity of Intravenous Bisphosphonates for the Treatment of Malignancy- Related Bone Disease

Renal dysfunction is a particularly problematic adverse event that requires additional management and can prohibit the use of certain medications. Due to their renal uptake and elimination, some bisphosphonates can cause nephrotoxicity when used for the treatment of skeletal-related events in patients with bone metastases. However, clinical studies and post-marketing experience indicate that renal effects do not appear to be the same for all bisphosphonates. Zoledronic acid and pamidronate appear to be associated with a greater risk of renal toxicity, especially when given in high doses or over short infusion times. In contrast, high loading doses of intravenous ibandronate (3 x 6 mg given on days 1-3) have shown no additional renal safety concerns, and intravenous ibandronate 6 mg appears to have a renal safety profile comparable to placebo. This paper reviews the renal safety of intravenously administered bisphosphonates and makes some suggestions, based on preclinical and clinical data, as to why renal safety profiles may differ.