Elimination and clearance of pamidronate by haemodialysis (Brief Communication)

Elimination of intravenous alendronate by hemodialysis: A kinetic study

INTRODUCTION

The potential utility of intravenous alendronate for the treatment of osteoporosis in hemodialysis patients was recently reported. However, the pharmacokinetics of intravenous alendronate in patients on hemodialysis is not clear.

METHODS

Six hemodialysis patients (mean age, 80.5 years) with osteoporosis who had received intravenous alendronate prior to the study were enrolled. The participants received a 30-min infusion of 900-μg alendronate intravenously at the beginning of the dialysis session. The blood flow rate (Qb) and dialysate flow rate (Qd) were set at 200 mL/min and 500 mL/min, respectively. All patients used the same dialyzer (1.5-m² polysulfone membrane). At the completion of administration, plasma and dialysate samples were collected, and alendronate concentrations were determined using metal-free high-performance liquid chromatography (HPLC)-tandem mass spectrometry (MS/MS).

RESULTS

The plasma arterial alendronate concentration was 150.9 ± 46.09 ng/mL. It decreased through the dialyzer to 76.1 ± 34.1 ng/mL (venous alendronate concentration). Mean alendronate clearance was 113.9 ± 25.6 mL/min. Mean alendronate removal by hemodialysis, measured by the difference in arterial-venous concentrations, was 51.8%.

CONCLUSIONS

Fifty percent of intravenous alendronate was removed by hemodialysis, which is nearly equal to elimination of alendronate in patients with normal renal function. The elimination by hemodialysis would decrease the risk of excessive accumulation in bone. UMIN 000027182.

Pharmacology of bisphosphonates

The biological effects of the bisphosphonates (BPs) as inhibitors of calcification and bone resorption were first described in the late 1960s. In the 50 years that have elapsed since then, the BPs have become the leading drugs for the treatment of skeletal disorders characterized by increased bone resorption, including Paget's disease of bone, bone metastases, multiple myeloma, osteoporosis and several childhood inherited disorders. The discovery and development of the BPs as a major class of drugs for the treatment of bone diseases is a paradigm for the successful journey from "bench to bedside and back again". Several of the leading BPs achieved "blockbuster" status as branded drugs. However, these BPs have now come to the end of their patent life, making them highly affordable. The opportunity for new clinical applications for BPs also exists in other areas of medicine such as ageing, cardiovascular disease and radiation protection. Their use as inexpensive generic medicines is therefore likely to continue for many years to come. Fifty years of research into the pharmacology of bisphosphonates have led to a fairly good understanding about how these drugs work and how they can be used safely in patients with metabolic bone diseases. However, while we seemingly know much about these drugs, a number of key aspects related to BP distribution and action remain incompletely understood. This review summarizes the existing knowledge of the (pre)clinical and translational pharmacology of BPs, and highlights areas in which understanding is lacking.

Use of Pamidronate to Treat Hypercalcemia in an Oncology Dialysis Patient: A Case Report

Patient: Female, 60

Final Diagnosis: Hypercalcemia secondary to malignancy

Symptoms: Hypercalcemia

Medication: —

Clinical Procedure: —

Specialty: Nephrology

SNF472, a novel inhibitor of vascular calcification, could be administered during hemodialysis to attain potentially therapeutic phytate levels

BACKGROUND

Cardiovascular calcification (CVC) is a major concern in hemodialysis (HD) and the loss of endogenous modulators of calcification seems involved in the process. Phytate is an endogenous crystallization inhibitor and its low molecular mass and high water solubility make it potentially dialyzable. SNF472 (the hexasodium salt of phytate) is being developed for the treatment of calciphylaxis and CVC in HD patients. We aimed to verify if phytate is lost during dialysis, and evaluate SNF472's behaviour during dialysis.

METHODS

Dialyzability was assessed in vitro using online-hemodiafiltration and high-flux HD systems in blood and saline. SNF472 was infused for 20 min and quantified at different time points.

RESULTS

Phytate completely dialyzed in 1 h at low concentrations (10 mg/l) but not when added at 30 or 66.67 mg/l SNF472. In bypass conditions, calcium was slightly chelated during SNF472 infusion but when the system was switched to dialysis mode the calcium in the bath compensated this chelation.

CONCLUSION

Phytate dialyses with a low clearance. The administration of SNF472 as an exogenous source of phytate allows to attain supra-physiological levels required for its potential therapeutic properties. As SNF472 is infused during the whole dialysis session, the low clearance would not affect the drug's systemic exposure.

Use of denosumab in a dialysis patient with bone metastases from breast cancer and hepatorenal polycystic disease: a case report

Cancer patients with severe renal dysfunction represent a challenge for the physician. This is the first case report on the use of denosumab in a dialysis patient with bone metastases. We present the clinical case of a 45-year-old woman who had hepatorenal polycystic disease, diagnosed during childhood, and stage IV chronic kidney failure at the time of breast cancer diagnosis. Three years after surgery plus adjuvant hormonal therapy she suffered a further worsening of renal function, requiring dialysis, and very advanced bone metastasis in the hip with severe pain. As pamidronate was the only bone agent available in the center, she received it for 4 months (before a dialysis session), during which time the bone metastases stabilized. In March 2014, the patient switched to denosumab (which had become available in the center), and continued with hormone therapy. Seven months after denosumab initiation, the patient had almost complete pain relief, and the bone metastases exhibited radiological improvement. The tolerability was excellent, without any related adverse event. There were no changes in albumin-adjusted serum calcium, serum phosphorus, and intact parathyroid hormone, except for a transient and mild hypocalcemia at 3 months and an increase in intact parathyroid hormone levels, which required adjustment of vitamin D analog dose. Denosumab can be administered to prevent skeletal-related events in patients with bone metastasis from solid tumors and severely impaired renal function, even in those requiring dialysis. In this particular patient, the safety was good.

Pharmacology of Bisphosphonates in Patients with Chronic Kidney Disease

Bisphosphonates are medications which bind strongly to mineral. They are ingested by osteoclasts and inhibit an enzyme necessary for bone resorption. The gastrointestinal absorption is poor and the only method of excretion is renal. Therefore, in patients with CKD the body accumulates a higher percentage of a dose of bisphosphonate. These medications remain attached to bone mineral for many years. Although the primary action is to inhibit bone resorption, secondarily bone formation is also inhibited, and in patients with CKD bisphosphonate use often leads to adynamic bone. In some experimental models in animals, the bisphosphonates can inhibit vascular calcification but this effect has not been seen in humans. Intravenous bisphosphonates may cause renal damage but oral doses do not reduce creatinine clearance. In stage 3 CKD, in patients who still have normal PTH, calcium, and alkaline phosphatase, randomized trials show similar benefits as in patients without CKD. Data from stage 4 and 5 CKD are very limited and no clear benefit has been shown.

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.

Effects of pamidronate and calcitriol on the set point of the parathyroid gland in postmenopausal hemodialysis patients with secondary hyperparathyroidism

BACKGROUND/AIMS

Secondary hyperparathyroidism may worsen after the administration of pamidronate in postmenopausal hemodialysis (HD) patients. The aim of this study was to evaluate the short-term effect of coadministration of calcitriol and pamidronate on dynamic parathyroid hormone (PTH) secretion.

METHODS

Fifteen postmenopausal women undergoing regular HD with serum intact PTH levels of >200 pg/ml were enrolled. The PTH-ionized calcium (iCa) curve was evaluated by the response to hypo- and hypercalcemia induced with 1 and 4 mEq/l of dialysate calcium, respectively. Parameters were compared after pamidronate was administered and after coadministration of pamidronate and calcitriol. Changes in serum levels of maximal serum PTH (PTHmax), basal PTH (PTHbase) and minimal PTH (PTHmin) were evaluated.

RESULTS

Pamidronate therapy resulted in a decrease in predialysis basal plasma iCa (p < 0.05) and an increase in PTHmax (p < 0.01), PTHbase (p < 0.01) and PTHmin (p < 0.01). The change in serum iCa and PTH was reversed after the coadministration of calcitriol and pamidronate.

CONCLUSION

Our study demonstrated that pamidronate therapy is associated with a reduced plasma iCa and increased PTH secretion. These adverse effects may be reversed by calcitriol. These findings suggest that in considering pamidronate treatment in postmenopausal patients with osteoporosis receiving HD, it might be safer to add calcitriol to prevent the increased PTH secretion.

Can bisphosphonates play a role in the treatment of children with chronic kidney disease?

In patients with chronic kidney disease (CKD) renal osteodystrophy, in the form of either low- or high-turnover bone disease, is quite common. While renal transplantation is expected to reverse renal osteodystrophy, long-term treatment with glucocorticoids before and/or after transplantation may lead to osteoporosis instead. Osteoporosis is defined as a skeletal disease with low bone mineral density, microarchitectural deterioration, and concomitant fragility. In adults, bisphosphonates are widely used to treat osteoporosis and other diseases associated with excessive bone resorption. In pediatric CKD patients the efficacy and safety of these drugs have not yet been addressed adequately and thus no evidence-based recommendations regarding the optimal type of bisphosphonate, dosage, or duration of therapy are available. Furthermore, while in adults the determination of areal bone mineral density is sufficient to diagnose osteoporosis, this is not the case in children. Instead, in pediatric patients, careful morphological assessment of bone structure and formation is required. Indeed, data from studies with uremic rats indicated that bisphosphonates, via a deceleration of bone turnover, have the potential not only to aggravate pre-existing adynamic bone disease, but also to impair longitudinal growth. Thus, the widespread use of bisphosphonates in children with CKD should be discouraged until the risks and benefits have been carefully elucidated in clinical trials.

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.

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.