Pharmacokinetics of pamidronate disodium in patients with cancer with normal or impaired renal function

Enhancing the Oral Rehabilitation and Quality of Life of Bisphosphonate-Treated Patients: The Role of Dental Implants

The purpose of this review is to examine the literature on the topic of bisphosphonate-related osteonecrosis of the jaw (BRONJ) and dental implant failure in patients undergoing bisphosphonate (BP) therapy who also received dental implants before, during, or after BP treatment, as compared to healthy patients. This research followed the guidelines in the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement. The "PICO" or population, intervention, comparison, and outcome clinical question was as follows: does the insertion of dental implants in patients receiving bisphosphonate therapy increase the failure and loss of implants or the incidence of bisphosphonate-related osteonecrosis of the jaw compared to healthy patients? The articles published in PubMed/Medical Literature Analysis and Retrieval System Online (MEDLINE) up to July 1, 2023, were retrieved using a mix of Medical Subject Heading (MeSH) words and their entry terms. The absence of randomized clinical trials examining this issue underscores the need for additional studies with extended follow-ups to answer outstanding questions. Because of the potential for BRONJ and implant failure, patients receiving bisphosphonate medication should exercise caution when planning dental implant surgery. In addition, when such procedures are carried out, the patient's entire systemic condition must be considered.

Cancer induced bone pain: current management and future perspectives

Recent improvements in the therapeutic armamentarium of oncology by the addition of targeted and immunotherapeutic agents have led to an increase in the life expectancy of advanced-stage cancer patients. This has led to an increased number of patients presenting with bone metastasis and experiencing episodes of cancer-induced bone pain (CIBP). CIBP is a crippling, chronic, morbid state interfering significantly with the functional capacity and the quality of life (QoL). CIBP is characterized by a complex multifactorial pathophysiological mechanism involving tumor cells, bone cells, inflammatory microenvironment, and the neuronal tissue. It may not be possible to mitigate pain completely; therefore, the aim should be to reach the lowest possible level of pain that allows for an acceptable QoL to the patient. Multimodality approach of surgical, radiation, medical and behavioral techniques is thus recommended to manage CIBP. This review discusses the pathogenesis and pathophysiological mechanism accompanying bone metastasis and CIBP, currently approved therapies for the management of CIBP, and the future perspective.

On the pharmacological evaluation of bisphosphonates in humans

One of the key parameters for a successful treatment with any drug is the use of an optimal dose regimen. Bisphosphonates (BPs) have been in clinical use for over five decades and during this period clinical pharmacokinetic (PK) and pharmacodynamic (PD) evaluations have been instrumental for the identification of optimal dose regimens in patients. Ideal clinical PK and PD studies help drug developers explain variability in responses and enable the identification of a dose regimen with an optimal effect. PK and PD studies of the unique and rather complex pharmacological properties of BPs also help determine to a significant extent ideal dosing for these drugs. Clinical PK and PD evaluations of BPs preferably use study designs and assays that enable the assessment of both short- (days) and long-term (years) presence and effect of these drugs in patients. BPs are mainly used for metabolic bone diseases because they inhibit osteoclast-mediated bone resorption and the best way to quantify their effects in humans is therefore by measuring biochemical markers of bone resorption in serum and urine. In these very same samples BP concentrations can also be measured. Short-term serum and urine data after both intravenous (IV) and oral administration enable the assessment of oral bioavailability as well as the amount of BP delivered to the skeleton. Longer-term data provide information on the anti-resorptive effect as well as the elimination of the BP from the skeleton. Using PK-PD models to mathematically link the anti-resorptive action of the BPs to the amount of BP at the skeleton provides a mechanism-based explanation of the pattern of bone resorption during treatment. These models have been used successfully during the clinical development of BPs. Newer versions of such models, which include systems pharmacology and disease progression models, are more comprehensive and include additional PD parameters such as BMD and fracture risk. Clinical PK and PD studies of BPs have been useful for the identification of optimal dose regimens for metabolic bone diseases. These analyses will also continue to be important for newer research directions, such as BP use in the delivery of other drugs to the bone to better treat bone metastases and bone infections, as well as the potential benefit of BPs at non-skeletal targets for the prevention and treatments of soft tissue cancers, various fibroses, and other cardiovascular and neurodegenerative diseases, and reduction in mortality and extension of lifespan.

Bisphosphonates in Dialysis and Transplantation Patients: Efficacy and Safety Issues

Bisphosphonates are an old class of compounds. They were used in the 1930s as antiscaling and anticorrosion agents in washing powders and water to prevent the deposition of calcium crystals. Those basic functions were later utilized in an attempt to prevent ectopic calcifications in humans. The early studies demonstrated that bisphosphonates had a strong affinity for bone. That property was first exploited when the compounds were used for “bone scans.”

Currently, the drugs are used for treatment of hypercalcemic conditions, abnormal bone remodelling, Paget disease, malignancy, and osteoporosis. Bisphosphonates have several important toxicities: acute renal failure, worsening renal function, reduced bone mineralization, and osteomalacia. For those reasons and others, this class of drugs has not yet been approved for use in children or in patients with severe renal insufficiency.

The present review covers several aspects of bisphosphonates: molecular structure, routes of administration, pharmacology, mechanisms of action, toxicities, and exceptional uses in children with renal disease.

Use of Pamidronate for Hypercalcemia of Malignancy in Renal Dysfunction

BACKGROUND

Few studies have been conducted investigating the use of bisphosphonates in hypercalcemia of malignancy (HCM) in the setting of renal dysfunction.

OBJECTIVE

The primary objective was to compare the incidence of acute kidney injury (AKI) within 7 days of receiving pamidronate for the treatment of HCM with pre-existing renal dysfunction versus normal renal function at the time of pamidronate administration. The secondary objectives explored the effects of pamidronate doses and infusion rates on the safety and efficacy in those with pre-existing renal dysfunction for the treatment of HCM.

METHODS

A retrospective chart review was conducted on patients who received pamidronate for the treatment of HCM at a community teaching hospital in Indianapolis, Indiana, from January 1, 2013, to May 31, 2017.

RESULTS

A total of 141 pamidronate administrations were included (116 patients had normal baseline renal function, and 25 patients had pre-existing renal dysfunction before pamidronate administration for the treatment of HCM). Two (8%) patients developed AKI in the pre-existing renal dysfunction group, compared with 4 (3.4%) patients in those without pre-existing renal dysfunction (P = .288). For those with pre-existing renal dysfunction, the incidence of AKI did not differ based on the dosage of pamidronate given (P = .762) or infusion rates (P = .373).

CONCLUSION

Pamidronate appears to have limited impact on renal function at doses up to 90 mg in the setting of pre-existing renal dysfunction for the treatment of HCM.

Effect of intravenous administration of zoledronic acid on jaw bone density in cases having skeletal metastasis: A prospective clinical study

AIM

The objective is to evaluate the effect of intravenous (i.v.) administration of bisphosphonate (zoledronic acid) therapy on the jaw bone density and incidence of any other bony patholog.

SETTINGS AND DESIGN

Observational - prospective study.

MATERIALS AND METHODS

A total of 57 patients having a history of bony metastasis (excluding the jaw bone) were enrolled following the inclusion/exclusion criteria. Each patient received six doses of 4 mg i.v. bisphosphonate once a month. Multidetector computed tomography (MDCT) of jawbones for each patient was performed before the start of therapy (baseline) and subsequently at 6 and 12 months. Bone density was assessed at 24 predetermined sites (8 sites in maxilla and 16 sites in mandible) and any pathological change in either of the jaw bones was noted.

STATISTICAL ANALYSIS USED

Shapiro-Wilk test ,Pearson's Chisquare test and repeated measures analysis of variance.

RESULTS

The result showed no statistically significant increase in mean bone density over a period of 1 year in maxilla and mandible. However, a significant increase in bone density was observed from 6 months to 1 year in mandibular anterior cancellous bone. The detailed observation of each MDCT scan showed no pathological change in either of the jaw bones during the study period.

CONCLUSION

The administration (i.v.) of six doses of 4 mg bisphosphonate did not lead to a significant change in bone density over a period of 1 year.

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.

Role of Pamidronate Disodium in the Treatment of Metastatic Bone Disease

Aims and Background

Bone metastases are a common feature of advanced neoplastic disease and are considered to be among the most frequent causes of pain and complications in oncologic patients. The main objective of the treatment of such patients is to control their symptoms and improve their quality of life. Pamidronate disodium is a second-generation bisphosphonate capable of inhibiting bone resorption (particularly osteoclast activity) without affecting bone reminerali-zation. After a brief introduction concerning the pathophysiology of bone metastases and neoplastic bone pain, we herein present data on the clinical pharmacology and toxicity of bisphosphonates in general, and pamidronate in particular. We conclude by reviewing the literature on the use of pamidronate in phase II and III trials involving patients with metastatic bone disease.

Methods

The paper is based on a review of articles published between 1984 and 1997 selected from the Cancerline and Medline databases.

Results

In the considered phase II and III studies involving patients with bone metastases (breast cancer and multiple myeloma in particular), pamidronate proved to be efficacious in reducing the incidence of pain and skeletal complications, decreasing the excretion of metabolic markers of bone resorption and improving the quality of life. Intravenous infusions of 60-90 mg over a period of 2 hr every 3-4 weeks did not cause any significant toxic effects and was easily managed.

Conclusions

Pamidronate is a bisphosphonate that is efficacious in the treatment of symptomatic bone metastases and can be considered an important therapeutic option in association with systemic treatments, radiotherapy and normal supportive care, especially in patients with breast cancer and multiple myeloma. Further randomized studies are necessary to confirm the positive preliminary results in other neoplasms, analyze the cost/benefit ratio of the treatment, and verify the possibility that, in addition to being used for palliative purposes, pamidronate may also prevent or delay the appearance of bone metastases.

European Myeloma Network guidelines for the management of multiple myeloma-related complications

The European Myeloma Network provides recommendations for the management of the most common complications of multiple myeloma. Whole body low-dose computed tomography is more sensitive than conventional radiography in depicting osteolytic disease and thus we recommend it as the novel standard for the detection of lytic lesions in myeloma (grade 1A). Myeloma patients with adequate renal function and bone disease at diagnosis should be treated with zoledronic acid or pamidronate (grade 1A). Symptomatic patients without lytic lesions on conventional radiography can be treated with zoledronic acid (grade 1B), but its advantage is not clear for patients with no bone involvement on computed tomography or magnetic resonance imaging. In asymptomatic myeloma, bisphosphonates are not recommended (grade 1A). Zoledronic acid should be given continuously, but it is not clear if patients who achieve at least a very good partial response benefit from its continuous use (grade 1B). Treatment with erythropoietic-stimulating agents may be initiated in patients with persistent symptomatic anemia (hemoglobin <10g/dL) in whom other causes of anemia have been excluded (grade 1B). Erythropoietic agents should be stopped after 6-8 weeks if no adequate hemoglobin response is achieved. For renal impairment, bortezomib-based regimens are the current standard of care (grade 1A). For the management of treatment-induced peripheral neuropathy, drug modification is needed (grade 1C). Vaccination against influenza is recommended; vaccination against streptococcus pneumonia and hemophilus influenza is appropriate, but efficacy is not guaranteed due to suboptimal immune response (grade 1C). Prophylactic aciclovir (or valacyclovir) is recommended for patients receiving proteasome inhibitors, autologous or allogeneic transplantation (grade 1A).

Current Controversies in the Management of Myeloma Bone Disease

Recent significant advances in the treatment of multiple myeloma have resulted in an improvement in median overall survival from 4.6 years, for patients diagnosed between 2001 and 2005, to 6.1 years, for those diagnosed between 2006 and 2010 (Kumar et al., 2014). However, myeloma bone lesions persist in the absence of active disease and continue to be frequent and significant causes of patient morbidity and contribute to mortality. While bisphosphonate therapy in combination with anti-myeloma therapy remains the cornerstone of skeletal disease management in myeloma, open questions regarding the optimal management of patients with myeloma bone disease remain. This article will address when to initiate and stop bone-targeted therapy in patients with monoclonal gammopathies, duration of bisphosphonate treatment in the era of more effective anti-myeloma treatment, the role of bone resorption markers in determining the dosing schedule for anti-resorptive therapy, risks and benefits of long term anti-resorptive therapy, and whether anti-resorptive therapies should be stopped to enhance the potential anabolic effects of proteasome antagonists and other anabolic agents. J. Cell. Physiol. 231: 2374-2379, 2016. © 2016 Wiley Periodicals, Inc.

Current Trends of Renal Impairment in Multiple Myeloma

BACKGROUND

Renal impairment (RI) is a common complication of multiple myeloma (MM). Around 50% of patients with MM have RI at presentation, and up to 5% require dialysis treatment. Severe acute kidney injury (AKI) as a cause of RI is a particular challenge as historically the survival of patients who sustain this complication and require dialysis is very poor. However, in this current period, survival is improving and the focus is on optimum use of novel chemotherapies and the evaluation of extra-corporeal therapies for removal of serum immunoglobulin light chains.

SUMMARY

RI in patients with MM is commonly associated with excess monoclonal free light chain (FLC) production; myeloma cast nephropathy is the predominant renal pathology in patients presenting with severe RI secondary to AKI. The majority of patients have mild to moderate RI and recover renal function. However, patients with more severe RI, in particular those with a requirement for dialysis, are less likely to recover renal function. Rapid diagnosis and prompt institution of anti-myeloma therapy is an important determinant of renal function recovery, through targeting early and sustained reduction of involved monoclonal FLC. Novel agents are associated with excellent disease response, and bortezomib is now widely used as a first-line agent in the management of MM in patients with severe RI. Extended haemodialysis using high cut-off dialysers is more effective for extracorporeal removal of FLC than plasma exchange, and clinical trials are in process. High-dose chemotherapy with autologous stem cell transplantation does have a role in patients with severe RI but requires careful patient selection.

KEY MESSAGES

RI is very common in patients with MM, and renal function recovery is associated with improved clinical outcomes. We summarise the epidemiology of MM in the UK, present the impact of RI and renal function recovery on patient outcome, and describe the current management of MM in western countries.

FACTS FROM EAST AND WEST

(1) A serum creatinine level >2 mg/dl has been reported in 16, 21, 24, and 33% of patients with MM in cohort studies from Japan, Europe, China, and Korea, respectively. A creatinine clearance rate <30 ml/min was observed in 30 and 15% of patients in Chinese and Western MM cohorts, respectively. The commonest cause of severe RI in patients with MM is myeloma cast nephropathy. (2) The efficacy of novel treatments (bortezomib, carfilzomib, thalidomide, and lenalidomide) has predominantly been assessed in Western patients. Bortezomib and dexamethasone are the current standard of care for MM and severe RI in the West. Severe RI is not a contraindication to autologous stem cell transplantation (ASCT). Most of the data are from the West; there are case reports from China describing good outcomes with ASCT. The removal of FLC by high-cut-off hemodialysis is under evaluation in randomized controlled trials (RCTs) in the West. Studies in this area are not yet conducted in China. In China, new treatments, such as bortezomib, are more widely used than before, and favorable results are being reported; however, RCT studies are still needed in this area to confirm the efficacy and safety of this and other novel treatments.

Quality and Outcomes of Treatment of Hypercalcemia of Malignancy

Using a nationwide database, 4,874 patients with hypercalcemia of malignancy were identified. The in-hospital mortality rate was 6.8%. Overall, 1,971 (40.4%) patients received pamidronate and 1,399 (28.7%) received zoledronic acid during hospitalization. Calcitonin was utilized in 1,337 (27.4%) patients while glucocorticoids were administered to 1,311 (26.9%). Use of contraindicated medications was noted in 136 (2.8%) patients who received thiazide diuretics and 12 (0.2%) who received lithium. Tumor site, presence of bone metastases, and severity of illness were predictors of treatment. There was no association between treatment with bisphosphonates, calcitonin, or glucocorticoids and morbidity or mortality.

Is retention of zoledronic acid onto bone different in multiple myeloma and breast cancer patients with bone metastasis?

Zoledronic acid (Zol) is used to treat bone disease in both multiple myeloma (MM) and breast cancer patients with bone metastasis (BC). However, bones of MM and BC patients show a difference in retention of the bisphosphonate used for bone scintigraphy. Therefore, we hypothesized that disease-specific factors may differently influence Zol retention in MM and BC patients. We tested this hypothesis in an investigator initiated phase II clinical trial in which we compared the whole-body retention (WBrt) of Zol in a cohort of 30 multiple myeloma (MM) and 30 breast cancer (BC) (20 Zol naive and 40 with six or more previous administrations). On average, 62% of the administered Zol was retained in the skeleton of both MM and BC patients and independently of the number of treatments. WBrt of Zol did not correlate with cross-linked C-telopeptide (CTX) levels, but linear regression analyses showed that WBrt of Zol correlated with bone-specific alkaline phosphatase (bALP) levels in BC (p = 0.001), and with CTX/bALP in Zol naive MM patients (p = 0.012). Especially in BC patients, WBrt correlated with age (p = 0.014) independently of kidney function. In MM patients WBrt was found to primarily correlate with the extent of bone disease (p = 0.028). Multivariate linear regression analyses of the entire cohort pointed out that WBrt of Zol was best predicted by age (p < 0.000), osseous lesions (p < 0.001), and the preceding Zol dosing (p < 0.005) (r(2)  = 0.97). Comparing bone scintigrams with CT/X-ray images showed a poor correlation between sites of active bone disease and binding of scintigraphy bisphosphonate in 36% of MM patients and in 13% of BC patients. We conclude that WBrt of Zol is primarily determined by two non-disease related factors and only one disease related, but that there may be differences in retention or drug delivery at individual sites of bone disease between MM and BC patients. In order to find the optimal dosing of Zol, these observations should be taken into account.

Renal Safety and Pharmacokinetics of Ibandronate in Multiple Myeloma Patients With or Without Impaired Renal Function

In this open-label study, the authors assessed the pharmacokinetics and safety of ibandronate in patients with multiple myeloma and varying renal function. Renal deterioration was graded at baseline depending on creatinine clearance in 4 stages (0: >80; 1: 50-79; 2: 30-49, and 3: <30 mL/min). Patients (n = 40) received intravenous ibandronate 6 mg (30-minute infusion). Ibandronate excretion and serum levels were measured over 24 hours. Serum creatinine, creatinine clearance, and markers of tubular damage were monitored before ibandronate infusion and at 24 and 72 hours following ibandronate infusion. Ibandronate clearance, AUC(0-24), AUC(0-infinity), serum t((1/2)), and C(max) were calculated. There was a significant positive correlation between ibandronate clearance and creatinine clearance (r = 0.858; P < .00001). The AUC for grade 3 renal insufficiency increased by approximately 60% versus grade 0 (P < .01) but was not significantly different between other grades of renal function. The t((1/2)) did not increase significantly, and peak serum levels of ibandronate were similar for the 4 grades of renal function. Serum creatinine, creatinine clearance, and markers of tubular damage did not change significantly within 72 hours of ibandronate infusion. Despite renal function already being compromised in this patient group, there was no evidence of acute nephrotoxicity with ibandronate.

Dental complications and management of patients on bisphosphonate therapy: A review article

Bisphosphonates are group of drugs that inhibit bone resorption and are used to treat a range of pathologies including Paget's disease, osteoporosis, multiple myeloma and metastasis associated with breast or prostate cancer. The most common complication in patients on bisphosphonate therapy is osteonecrosis of jaw (ONJ) which can occur after any surgical dental procedure and the risk for the development of osteonecrosis of jaw is higher in patients receiving intravenous bisphosphonate therapy than in patients receiving oral bisphosphonate therapy. Typical presentation is in the form of non-extraction socket, presence of exposed bone, gingival swelling or purulent discharge, when local debridement and antibiotics are ineffective. At present, there is no effective treatment for bisphosphonate induced osteonecrosis, so prevention is extremely important. Maximum precautions should be taken in patients who are at the risk of development of ONJ especially when any dental surgical procedure like extractions, retrograde apicoectomies, periodontal surgery and implant placement is contemplated. Dentists and oral or maxillofacial surgeon must keep up to date with the latest approaches or guidelines to prevention and the risk factors, particularly when treating patients who are on bisphosphonates, or who will be taking bisphosphonates.

Long-term treatment with alendronate increases the surgical difficulty during simple exodontias - an in vivo observation in Holtzman rats

Background

Atraumatic teeth extractions protocols are highly encouraged in patients taking bisphosphonates (Bps) to reduce surgical trauma and, consequently, the risk of jaws osteonecrosis development. In this way, this paper aims to report the findings of increased surgical difficulty during simple exodontias in animals treated with bisphosphonates.

Methods

Sixty male Holtzman rats were randomly distributed into three groups of 20 animals and received daily subcutaneous administration of 1 mg/kg (AL1) or 3 mg/kg (AL3) of alendronate or saline solution (CTL). After 60 days of drug therapy all animals were submitted to first lower molars extractions under general anesthesia. Operatory surgical time and the frequency of teeth fractures were measured as principal outcomes and indicators of surgical difficulty degree.

Results

Animals treated with alendronate (AL1 and AL3) were associated to higher operatory times and increased frequency of teeth fractures compared to match controls.

Conclusions

The bisphosphonate therapy may be associated with an increased surgical difficulty and trauma following simple exodontias protocols, which is considered a critical issue when it comes to osteonecrosis development.

Effects of pamidronate on human alveolar osteoblasts in vitro

PURPOSE

Administration of bisphosphonates has recently been associated with the development of osteonecrotic lesions of the jaw (ONJ). To elucidate the potential contributions of osteogenic cells to the development and regeneration of ONJ, we have isolated primary cells from human alveolar and long/iliac bones, and examined the effects of pamidronate on cell viability, proliferation, osteogenesis, and wound healing.

MATERIALS AND METHODS

Primary human osteoblasts and bone marrow stromal cells were isolated from alveolar and iliac/long bone and marrow tissue. Cellular proliferation, alkaline phosphatase activity, apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling, caspase-3, and 4,6-diamidino-2-phenylindole dihydrochloride assays) and wound healing in an in vitro scratch assay were assessed after exposure to pamidronate at a range of clinically relevant doses.

RESULTS

Primary alveolar osteoblasts proliferated at significantly higher rates than long/iliac bone osteoblasts in vitro. Upon exposure of alveolar osteoblasts and long/iliac bone marrow stromal cells to pamidronate for more than 72 hours, we have observed significantly decreased cell viability, proliferation, osteogenesis, and in vitro wound healing at ≥6 × 10(-5) mol/L pamidronate, with the induction of apoptosis in approximately 20% of cell population.

CONCLUSIONS

The remodeling activity of alveolar bone, indicated by higher proliferation of alveolar osteoblasts, could be negatively affected by exposure to high concentrations of pamidronate over extended periods. The absence of anabolic effects of pamidronate on alveolar osteoblasts and the induction of apoptosis in osteogenic cells could negatively affect bone balance at this site and contribute to osteonecrosis of the jaw.

Possible role of oral ibandronate administration in Osteonecrosis of the Jaw: a case report

We describe a case of Osteonecrosis of the Jaw (ONJ) that developed in a 65-year-old Caucasian woman with osteopenia and other risk factors who was receiving low doses of oral bisphosphonate therapy (ibandronate, 150 mg monthly). Computed tomography (CT), panoramic radiographs (OPT), 99mTc-Sn-MDP scintigraphy, and magnetic resonance imaging (MRI) were performed to study the diseased area; cytological examination also revealed the presence of suppurative material around the area of exposed bone. A diagnosis of bisphosphonate-related osteonecrosis of the jaw complicated by osteomyelitis was made. The patient was prescribed a drug protocol consisting of metronidazole 250 mg 2 times daily, chlorhexidine mouthwashes 3 times daily and chewing exercises for two months. Ibandronate was stopped and replaced with strontium ranelate. The symptoms improved and the patient is still under close follow-up. Assessment of the benefits versus risks is particularly necessary in patients with several risk factors to ascertain their eligibility for treatment with antiresorptive drugs and when this is not possible to choose alternative medications.

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.

Pharmacology of bisphosphonates

Four decades of preclinical and clinical research of the pharmacology of bisphosphonates have generated data and concepts that have considerably improved their clinical use. However, despite this progress several pharmacological aspects relevant to bisphosphonate action on bone are still incompletely understood. This is mainly due to the complex, unique pharmacological properties of bisphosphonates. We review here the pharmacokinetic and pharmacodynamic data of bisphosphonates that are relevant for their clinical application and for the potential choice of a given compound, focusing on uncertainties that still exist.

The backbone of progress--preclinical studies and innovations with zoledronic acid

Bisphosphonates (BPs) are antiresorptive agents that block pathologic bone resorption by inhibiting osteoclast function and later inducing osteoclast apoptosis. These agents localize to bone and break the vicious cycle of bone resorption that results from cross-stimulation between cancer cells and the bone remodeling cells, thereby reducing cancer-induced osteolysis and the tumor burden in bone. Thus nitrogen-containing BPs (N-BPs) have well established clinical benefits in the treatment of bone metastases from solid tumors and bone lesions from multiple myeloma. Preclinical data indicate that N-BPs, especially zoledronic acid (ZOL), can exert antimyeloma activity both in vitro and in vivo. Studies show that N-BPs can inhibit multiple intracellular processes essential for cancer cell proliferation and invasion and induce apoptosis. Furthermore, clinically relevant doses of N-BPs inhibit tumor-associated angiogenesis and can modulate macrophage phenotype in vivo, which is likely to contribute to anticancer effects.

Additive/synergistic antitumoral effects on prostate cancer cells in vitro following treatment with a combination of docetaxel and zoledronic acid

Once bone metastasized and androgen independent, prostate cancer is often associated with skeletal morbidity and disability. New treatment modalities that can palliate symptoms from the skeleton and inhibit further progression are warranted. In this study, the antitumoral effects following treatment with a combination of docetaxel and the new generation bisphosphonate, zoledronic acid, were investigated on two hormone-refractory prostate cancer cell lines: PC3 and DU145. The prostate cancer cells were treated with increasing concentrations of zoledronic acid in the absence or presence of docetaxel. Toxicity was measured using fluorometric microculture cytotoxic assay technique. A concentration of 25 microM, zoledronic acid reduced the viable cell number to 68% and 98% for PC3 and DU145 cells respectively. Docetaxel, on the other hand, at a concentration of 0.1 ng/ml, had no effect on the viability. However, a combination of zoledronic acid and docetaxel reduced the cell number to 60% and 81% respectively. Furthermore, zoledronic acid in the concentration range 12.5 microM-50 microM enhanced the antitumoral effects of docetaxel (0.01-1 ng/ml) in an additive and/or synergistic manner for both cell lines. These data support the hypothesis that zoledronic acid, in addition to having bone resorption inhibiting properties, also exhibits anti-tumoral effects. It also appears that combined treatment with docetaxel causes additive and/or synergistic cytostatic effects on prostate cancer cells.

Use of bisphosphonates for the treatment of stress fractures in athletes

A literature review was performed to investigate the potential role of bisphosphonates for the treatment of stress fractures in athletes. Given the inhibitory action on osteoclast-mediated bone resorption, short-term suppression of bone remodeling using bisphosphonates could potentially treat stress fractures and prevent stress fractures from becoming regular fractures. To date, while there are some animal studies showing the scientific basis of bisphosphonates on stress fractures, there is still no conclusive evidence to prove any effect of bisphosphonates on stress fracture healing in humans. Further well-designed clinical trials should be carried out to establish their usefulness and safety. Until the results are available, it is prudent to limit the use of bisphosphonates for the treatment of stress fractures.

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.

Osteonecrosis of the jaw complicating bisphosphonate treatment for bone disease in multiple myeloma: an overview with recommendations for prevention and treatment

Osteonecrosis of the Jaw (ONJ) is a recently recognised and potentially highly morbid complication of bisphosphonate therapy in the setting of metastatic malignancy, including myeloma. Members of the Medical and Scientific Advisory Group of the Myeloma Foundation of Australia formulated guidelines for the management of bisphosphonates around the issue of ONJ, based on the best available evidence in June 2008. Prior to commencement of therapy, patients should have an oral health assessment and be educated about the risks of ONJ. Dental assessment should occur 6 monthly during therapy. If tooth extraction is required, sufficient time should be allowed for complete healing to occur prior to commencement of bisphosphonate. As the risk of ONJ increases with duration of bisphosphonate therapy, we recommend annual assessment of dose with modification to 3 monthly i.v. therapy or to oral therapy with clodronate for those with all but the highest risk of skeletal-related event. Established ONJ should be managed conservatively; a bisphosphonate "drug holiday" is usually indicated and invasive surgery should generally be avoided. These recommendations will assist with clinical decision making for myeloma patients who are at risk of bisphosphonate-associated ONJ.

Biodistribution and plasma protein binding of zoledronic acid

The bisphosphonate zoledronic acid is a potent inhibitor of osteoclast-mediated bone resorption. To investigate drug biodistribution and elimination, (14)C-zoledronic acid was administered intravenously to rats and dogs in single or multiple doses and assessed for its in vitro blood distribution and plasma protein binding in rat, dog, and human. Drug exposure in plasma, bones, and noncalcified tissues was investigated up to 240 days in rats and 96 h in dogs using radiometry after dissection. Drug biodistribution in the rat and within selected bones from dog was assessed by autoradiography. Concentrations of radioactivity showed a rapid decline in plasma and noncalcified tissue but only a slow decline in bone, to approximately 50% of peak at 240 days post dose, whereas the terminal half-lives (50-200 days) were similar in bone and noncalcified tissues, suggesting redistribution of drug from the former rather than prolonged retention in the latter. Uptake was highest in cancellous bone and axial skeleton. At 96 h after dose, the fraction of dose excreted was 36% in rat and 60% in dog; 94 to 96% of the excreted radioactivity was found in urine. Blood/plasma concentration ratios were 0.52 to 0.59, and plasma protein binding of zoledronic acid was moderate to low in all species. The results suggest that a fraction of zoledronic acid is reversibly taken up by the skeleton, the elimination of drug is mainly by renal excretion, and the disposition in blood and noncalcified tissue is governed by extensive uptake into and slow release from bone.

Administration of pamidronate alters bone-titanium attachment in the presence of endotoxin-coated polyethylene particles

Bisphosphonates are promising in the treatment of periprosthetic osteolysis induced by particulate wear debris. The in vivo effects of pamidronate with different doses and durations of administration on bone-titanium attachment in the presence of endotoxin-coated polyethylene particles were examined in a rat model in this study. Titanium pins and endotoxin-coated polyethylene particles were introduced into rat femoral canals followed by intraperitoneal injection of pamidronate every other day. The treatment varied in the dose from 0 to 40 microg/kg and the duration of either 10 days or 6 weeks. Bilateral femurs were harvested after 6 weeks and examined by bone densitometer and MicroCT scan. Pamidronate increased the bone density of the left, unoperated femurs in a dose and duration dependent manner. Bone-titanium attachment significantly increased in all treatment groups compared to the control group. When pamidronate was administered for 10 days, the increase of bone-titanium attachment was significantly dose-dependent. However, when pamidronate was given for 6 weeks at 4 microg/kg, the bone-titanium attachment was significantly (p < 0.001) lower compared to the 10 day treatment of the same dose, although it was significantly higher than controls. Our results suggest that pamidronate effectively increase bone-titanium attachment even in the presence of endotoxin-coated polyethylene particles. However, long-term administration may reduce its efficacy.

Bisphosphonates and osteomyelitis of the jaw: a pathogenic puzzle

The maxillary and mandibular bones undergo high-turnover remodeling to maintain mechanical competence. Common dental or periodontal diseases can increase local bone turnover. Bisphosphonates (BPs) accumulate almost exclusively in skeletal sites that have active bone remodeling. The maxillary and mandibular bones are preferential sites for accumulation of BPs, which become buried under new layers of bone and remain biologically inactive for a long time. Surgical odontostomatological procedures create open bony wounds that heal quickly and without infection, as a result of activation of osteoclasts and subsequently osteoblasts. Once BPs are removed from the bone via activation of osteoclasts after a tooth extraction or a periodontal procedure, they induce osteoclast apoptosis. This inhibition of osteoclast bone resorption impairs bone wound healing because of decreased production of cytokines derived from the bone matrix, and the bone is exposed to the risk of osteomyelitis and necrosis. The pathogenic relationship between BPs and osteonecrosis of the jaw is unclear, but there is evidence to indicate an association between high-dose BP treatment and exposure to dental infections or oral surgical procedures. A better knowledge of the interactions between BPs and jaw and maxillary bone biology will improve clinical and therapeutic approaches.

A review of the literature on osteonecrosis of the jaw in patients with osteoporosis treated with oral bisphosphonates: prevalence, risk factors, and clinical characteristics

OBJECTIVE

This literature review was performed to elucidate the relationship between bisphosphonate use and development of osteonecrosis of the jaw (ONJ) in patients receiving oral bisphosphonates for the treatment of osteoporosis.

METHODS

MEDLINE, the Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, and EMBASE were searched for English-language articles published from 1966 to September 2006 whose titles included the term osteonecrosis of the jaw in conjunction with bisphosphonates, alendronate, risedronate, ibandronate, etidronate, clodronate, zoledronic acid, or pamidronate. Articles were included in the review if the population consisted of adults with ONJ; patients received bisphosphonates for the treatment of osteoporosis only; the reported data included baseline characteristics of the study population (age; sex; comorbidities; concomitant medications; history of dental surgery, trauma, or infection), characteristics of bisphosphonate treatment (specific bisphosphonate, dose, duration of treatment, mode of administration), clinical features of ONJ (signs, symptoms, site), the treatment protocol used to manage ONJ, or the prevalence of ONJ in patients with osteoporosis treated with bisphosphonates; and the publication involved a case report, case series, or observational study.

RESULTS

After application of the search strategy and the inclusion/exclusion criteria, 11 publications reporting 26 cases of ONJ in patients receiving bisphosphonates for the treatment of osteoporosis were included in the review. The most commonly affected site was the mandible (16 patients), followed by the maxilla (6 patients). Among the 23 patients whose age was reported, 18 (78%) were aged >or=60 years. Among the 23 patients whose sex was reported, only 3 (13%) were men. Of 15 patients with a history of invasive dental treatment, 12 (80%) had undergone dental surgery or experienced dental trauma at the site of ONJ. Among the 10 patients for whom the duration of bisphosphonate treatment was reported, no clear relationship between the duration of bisphosphonate treatment and the development of ONJ was observed.

CONCLUSIONS

Considering that millions of patients have been prescribed bisphosphonates for the treatment of osteoporosis, the relative prevalence of ONJ in these patients was low. Age >or=60 years, female sex, and previous invasive dental treatment were the most common characteristics of those who developed ONJ. However, it is not possible to draw further conclusions about the potential association between oral bisphosphonate use and ONJ in the identified studies because of incomplete reporting and the presence of confounding factors.

A phase II study of ZD6474 (Zactima, a selective inhibitor of VEGFR and EGFR tyrosine kinase in patients with relapsed multiple myeloma--NCIC CTG IND.145

Multiple myeloma is a disease in which angiogenesis is postulated to be a target for therapy. Based on this hypothesis, we conducted a phase II trial of ZD6474 (Zactima; a VEGFR inhibitor) 100 mg p.o. daily in patients with relapsed multiple myeloma. The primary efficacy endpoint was objective response as assessed by reduction in M protein. There were 18 patients with a mean age of 64 years. One patient was ineligible and one was not evaluable. Overall, ZD6474 was well tolerated and pharmacokinetic testing demonstrated that adequate drug levels were achieved. The most common drug-related adverse events were nausea, vomiting, fatigue, rash, pruritus, headache, diarrhea, dizziness, and sensory neuropathy, all of which were Grade I-II in severity. There were no drug-related serious adverse events. Laboratory adverse events were infrequent: one patient had Grade III anemia, and there were no Grade III changes in biochemistry. No significant QTc interval changes were seen. There were no responses in M protein levels. In conclusion, ZD6474 was well tolerated at a dose of 100 mg per day and achieved plasma levels predicted to inhibit VEGF signaling. However, this was not reflected in clinical benefit since none of the patients had a reduction in M protein.

International Society of Geriatric Oncology (SIOG) recommendations for the adjustment of dosing in elderly cancer patients with renal insufficiency

A SIOG taskforce was formed to discuss best clinical practice for elderly cancer patients with renal insufficiency. This manuscript outlines recommended dosing adjustments for cancer drugs in this population according to renal function. Dosing adjustments have been made for drugs in current use which have recommendations in renal insufficiency and the elderly, focusing on drugs which are renally eliminated or are known to be nephrotoxic. Recommendations are based on pharmacokinetic and/or pharmacodynamic data where available. The taskforce recommend that before initiating therapy, some form of geriatric assessment should be conducted that includes evaluation of comorbidities and polypharmacy, hydration status and renal function (using available formulae). Within each drug class, it is sensible to use agents which are less likely to be influenced by renal clearance. Pharmacokinetic and pharmacodynamic data of anticancer agents in the elderly are needed in order to maximise efficacy whilst avoiding unacceptable toxicity.

Pamidronate distribution in pediatric renal and rheumatologic patients

OBJECTIVE

To evaluate the distribution and elimination of pamidronate in a population of pediatric patients with renal and rheumatologic disease.

METHODS

Pamidronate whole blood levels were collected for the first 4 h after first exposure in 7 patients. The relationship between the rate of urinary excretion of pamidronate and bone formation or resorption was examined in 18 patients while receiving pamidronate at a total dose of 1 mg/kg/dose infused intravenously over a 4-h period. The urinary pamidronate clearances were correlated with renal function, calcium levels and measures of bone formation and resorption.

RESULTS

Pamidronate levels reached steady state concentrations of 0.9-1.5 microg/ml within 30 min and the clearance of the drug (mean+/-SE) from blood was 180.0+/-64.2 ml/kg/h with an elimination half-life of less than 1 h. The mean urinary excretion of 31.5+/-2.2% of the administered dose indicated that about 68% of the drug was incorporated into bone, confirming the uptake of pamidronate into bone was similar in pediatric patients compared to that previously reported for adults. Bone specific alkaline phosphatase, which is a marker for bone growth and formation, had significant correlation with the uptake of pamidronate into bone (p=0.002). No correlation was demonstrated with a marker for bone resorption (urinary N-telopeptide/creatinine ratio), or with creatinine clearance or calciuria when assessed 2 months after treatment.

CONCLUSION

Pamidronate at a dose of 1 mg/kg/dose every 2 months appears safe in the short term for pediatric patients, achieves relatively low whole blood pamidronate levels, and has similar skeletal uptake of pamidronate compared to adults.

Dental management of patients receiving oral bisphosphonate therapy

BACKGROUND

In light of the uncertainty surrounding the incidence of bisphosphonate-associated osteonecrosis of the jaw (BON) and concomitant risk factors, dentists have questioned how to manage the care of patients receiving oral bisphosphonate therapy. Expert panelists were selected by the American Dental Association Council on Scientific Affairs on the basis of their expertise in the relevant subject matter and on their respective dental or medical specialties, and the panel was tasked with developing guidance for dentists treating these patients.

METHODS

There are no data from clinical trials evaluating dental management of the care of patients receiving oral bisphosphonate therapy and, therefore, these recommendations are based on a thorough review of the available literature relating to bisphosphonate use and osteonecrosis of the jaw. After reviewing the literature, the panel developed these recommendations based on their expert opinion.

RESULTS

These panel recommendations focus on conservative surgical procedures, proper sterile technique, appropriate use of oral disinfectants and the principles of effective antibiotic therapy.

CONCLUSIONS

The recommendations are a resource for dentists to use in their practice, in addition to the dentist's own professional judgment, the information available in the dental and medical literature, and information from the patient's treating physician. The recommendations must be balanced with the practitioner's professional judgment and the individual patient's preferences and needs.

Elimination and clearance of pamidronate by haemodialysis (Brief Communication)

Pamidronate (APD), a third-generation bisphosphonate, has proven to be useful in haemodialysis (HD) patients with ectopic calcifications and hypercalcaemia. Little is known about bisphosphonates clearance in patients undergoing HD. The authors' main objective was to study HD removal and clearance of APD. In total, 23 HD-requiring anuric end-stage renal disease (ESRD) adult individuals (12 men) aged 61.7 +/- 13 (mean +/- SD) years were admitted into the study. APD clearance and elimination were evaluated by (99m)Technetium APD (half-life 6 h). In total, 1 mg of labelled APD was injected via the arteriovenous graft prior to the start of HD. Blood samples were then drawn from the arterial (predialyser) and venous (postdialyser) lines of the extracorporeal circuit 2 h after the HD onset. In a subgroup of patients (n: 15) the dialysate was collected and quantified during the three initial HD hours. Venous APD concentrations (postdialyser) were 72 + 7% of arterial (predialyser) concentrations. Mean APD clearance was 69.3 + 16.6 mL/min, and mean APD extraction during dialysis session was 31.6 + 10.1%. In the present study involving HD-requiring anuric ESRD patients APD was successfully eliminated by HD. At the dose administered here none of the participants reported adverse events. APD is a potentially useful drug to be administered to HD-requiring ESRD patients, the understanding of its removal during HD as well as its dialytic clearance allows for a safer management of a drug that is usually eliminated by renal excretion.

Pamidronate induced anti-proliferative, apoptotic, and anti-migratory effects in hepatocellular carcinoma

BACKGROUND/AIMS

The small GTPase of Ras and Rho families are widely involved in human tumorgenesis and metastasis. It has recently been reported that pamidronate inhibits the mevalonate pathway, which is required for the prenylation of the small GTPase. We demonstrated a possible beneficial use of pamidronate in the treatment of hepatocellular carcinoma (HCC).

METHODS

The effect of pamidronate on cell proliferation was analyzed with five hepatoma cell lines using MTT assay. Apoptosis was evaluated by staining with DAPI and a histon ELISA assay. A cell migration assay was performed using the Modified Boyden Chamber. To analyze anti-proliferation effect of pamidronate in vivo, tumor volumes were monitored with the intraperitoneal injection of pamidronate after subcutaneous inoculation of PLC/PRF/5 cells into nude mice.

RESULTS

Pamidronate inhibited cell growth for all hepatoma cell lines. The amount of membrane associated Ras and phosphorylated extracellular signal-regulated kinase 2 (ERK 2) were reduced after pamidronate treatment. Pamidronate increased apoptosis and cleavage of Caspase-3, and -9. Pamidronate suppressed membrane associated RhoA and cell motility. In vivo, tumor volumes were significantly suppressed by pamidronate at three weeks (P<0.03).

CONCLUSIONS

We conclude that pamidronate has therapeutic potential in inducing anti-proliferative, apoptotic, and anti-migratory effects in HCC.

Skeletal retention of bisphosphonate (pamidronate) and its relation to the rate of bone resorption in patients with breast cancer and bone metastases

Bisphosphonate pharmacokinetics may affect individual responses. Skeletal retention of pamidronate infused monthly to patients with bone metastases was highly variable (12-98%) and did not diminish with time, showing the capacity of the skeleton to retain large amounts of bisphosphonate. Relationships between skeletal retention of pamidronate and rate of bone resorption are complex and depend on previous treatment and the total amount of retained bisphosphonate.

INTRODUCTION

Bisphosphonates (BPs) given intravenously every 3-4 weeks are effective in the management of metastatic bone disease from breast cancer, but responses among patients vary, and it is not known whether current dose and dose intervals are appropriate for an individual patient. An influence of pharmacokinetics of BPs on antiresorptive action may contribute to this variation in response. To test this hypothesis, we determined the skeletal retention of intravenous pamidronate and its association to the rate of bone resorption in patients with bone metastases from breast cancer.

MATERIALS AND METHODS

In a cross-sectional study, 24-h urinary excretion of pamidronate and the biochemical marker of bone resorption N-terminal telopeptide of type 1 collagen and serum alkaline phosphatase were measured in 40 patients with bone metastases from breast cancer at the beginning, after 3-6 months, and after 1 year of treatment with intravenous pamidronate 90 mg every 3-4 weeks.

RESULTS AND CONCLUSIONS

Skeletal retention (dose--amount excreted into urine) 2 days after infusion varied between 12% and 98% (mean, 62%) of the administered dose, but there were no differences in retention between patients receiving pamidronate for the first time or after 3-6 months or after 1 year of treatment. Retention of pamidronate was related to the prevalent rate of bone turnover in previously untreated patients, whereas no such relationship was found in previously treated patients. Rate of bone resorption after treatment seemed to be related to the amount of pamidronate retained. During 1 year of treatment, retention of pamidronate remained constant, indicating no saturation of skeletal binding sites with treatment. The variability in retention among individual patients can be attributed to the number of available binding sites. This is related, however, to bone turnover only before the start of treatment. The apparent relationships between skeletal retention and antiresorptive effect could have implications for the design of optimal therapeutic regimens with BPs in patients with bone metastases from breast cancer.

Pharmacokinetics/pharmacodynamics of bisphosphonates: use for optimisation of intermittent therapy for osteoporosis

Bisphosphonates suppress osteoclast-mediated bone resorption and are widely used in the management of osteoporosis. Daily oral administration of alendronic acid and risedronic acid have been shown to reduce the risk of vertebral and non-vertebral fractures. Once-weekly regimens with these bisphosphonates are pharmacologically equivalent to daily regimens. Regimens with treatment-free intervals longer than 1 week present an attractive therapeutic option as they may offer additional patient convenience and long-term adherence to treatment. However, until recently, such regimens, usually referred to as intermittent or cyclical, have not shown any convincing antifracture efficacy in clinical trials, probably because of the empirical manner in which the design of these regimens has been approached. Investigation of pharmacokinetics/pharmacodynamics of bisphosphonates may help in the design of effective intermittent dosage regimens. Bisphosphonates are poorly absorbed from the gastrointestinal tract and about 50% of the absorbed drug is taken up selectively by the skeleton, while the rest is excreted unaltered in urine. Bisphosphonates exert their action at the bone surface, where they are taken up by the osteoclasts during bone resorption. Therefore, when describing the pharmacokinetics of bisphosphonates in relation to the pharmacodynamics, the amount of bisphosphonate at the skeleton should be accounted for. Few of the reported clinical pharmacokinetic studies addressed this issue. This is partly due to the absence of study design elements to account for skeletal binding of the drugs. Pharmacokinetic studies have also been hampered by technical difficulties in determining the concentration of bisphosphonates in serum and urine. Moreover, most clinical pharmacokinetic (but also pharmacokinetic/pharmacodynamic) studies have primarily used noncompartmental analysis, leaving out the distinct advantages of modelling and simulation techniques. Clinically, the primary action of bisphosphonates can be assessed by the measurement of biochemical markers of bone resorption. Recent studies indicate that the pattern of these markers during bisphosphonate treatment may be predictive of antifracture efficacy; however, only limited data are available for the development of pharmacokinetic/pharmacodynamic models that are able to predict the response of these markers to different treatment regimens with bisphosphonates. Recently, pharmacokinetic/pharmacodynamic models for response to bisphosphonates have been described and, at present, some of them are being used in the design of bisphosphonate regimens with long drug-free intervals.

Investigation of the effect of pamidronate disodium on the in vitro viability of osteosarcoma cells from dogs

OBJECTIVE

To determine the effect of pamidronate disodium on the in vitro viability of osteosarcoma cells and non-neoplastic cells from dogs.

SAMPLE POPULATION

3 osteosarcoma and 1 fibroblast cell lines derived from dogs.

PROCEDURE

Cell counts and cell viability assays were performed in cultures of osteosarcoma cells (POS, HMPOS, and COS31 cell lines) and fibroblasts after 24, 48, and 72 hours of incubation with pamidronate at concentrations of 0.001 to 1000 microM or with no drug (control treatment). Percentage viability was determined in cell samples for each concentration of pamidronate and each incubation time. A DNA fragmentation analysis was performed to assess bisphosphonate-induced apoptosis.

RESULTS

Osteosarcoma cell viability decreased significantly in a concentration- and time-dependent manner at pamidronate concentrations ranging from 100 to 1000 microM, most consistently after 48 and 72 hours' exposure. In treated osteosarcoma cells, the lowest percentage cell viability was 34% (detected after 72 hours' exposure to 1000 microM pamidronate). Conversely, 72 hours' exposure to 1000 microM pamidronate did not significantly reduce fibroblast viability (the lowest percentage viability was 76%). After 72 hours of exposure, pamidronate did not cause DNA fragmentation in POS or HMPOS cells.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that pamidronate may have the potential to inhibit osteosarcoma growth in dogs, possibly through a nonapoptotic mechanism. The clinical relevance of these in vitro findings remains to be determined, but administration of pamidronate may potentially be indicated as an adjuvant treatment in chemotherapeutic protocols used in dogs.

The purine transferase from Trypanosoma cruzi as a potential target for bisphosphonate-based chemotherapeutic compounds

We identified and tested bisphosphonates as inhibitors of a protozoan molecular target. Computational modeling studies demonstrated that these compounds are mimics of the natural substrate of the enzyme. The most potent bisphosphonates in vitro are pamidronate and risedronate, which inhibit the purine transferase from Trypanosoma cruzi in the micromolar range.