Dose dependent effects on bone resorption and formation of intermittently administered intravenous ibandronate

Effect of intermittent and daily regimens of minodronic Acid on bone metabolism in an ovariectomized rat model of osteoporosis

The goal of the study was to compare the effects of minodronic acid on bone mineral density (BMD) and bone turnover in a rat ovariectomized (OVX) osteoporosis model, using two intermittent treatment regimens (weekly and 4 continuous days every 4 weeks) and a daily regimen. Female F344 rats (age 14 weeks) underwent ovariectomy or a sham operation. Minodronic acid was orally administered at 0.042, 0.21, and 1.05 mg/kg in the intermittent regimens, and at 0.03 and 0.15 mg/kg in the daily regimen for 12 weeks from the day after surgery. Minodronic acid dose-dependently ameliorated the decreases in areal BMD of the lumbar vertebrae and femur, and volumetric BMD of total and trabecular bone in the distal femur. Minodronic acid also suppressed the increase in urinary deoxypyridinoline levels and reduced serum osteocalcin levels. In bone histomorphometry, all three minodronic acid regimens suppressed OVX-induced increases in bone turnover at the tissue level and ameliorated all structural indices, except that an effect on trabecular thickness only occurred with daily treatment. In conclusion, minodronic acid administered weekly or for 4 continuous days every 4 weeks suppressed increased bone resorption and BMD to a similar extent to that of a similar total dose given daily in a rat OVX model.

Extracellular matrix remodeling: the common denominator in connective tissue diseases. Possibilities for evaluation and current understanding of the matrix as more than a passive architecture, but a key player in tissue failure

Increased attention is paid to the structural components of tissues. These components are mostly collagens and various proteoglycans. Emerging evidence suggests that altered components and noncoded modifications of the matrix may be both initiators and drivers of disease, exemplified by excessive tissue remodeling leading to tissue stiffness, as well as by changes in the signaling potential of both intact matrix and fragments thereof. Although tissue structure until recently was viewed as a simple architecture anchoring cells and proteins, this complex grid may contain essential information enabling the maintenance of the structure and normal functioning of tissue. The aims of this review are to (1) discuss the structural components of the matrix and the relevance of their mutations to the pathology of diseases such as fibrosis and cancer, (2) introduce the possibility that post-translational modifications (PTMs), such as protease cleavage, citrullination, cross-linking, nitrosylation, glycosylation, and isomerization, generated during pathology, may be unique, disease-specific biochemical markers, (3) list and review the range of simple enzyme-linked immunosorbent assays (ELISAs) that have been developed for assessing the extracellular matrix (ECM) and detecting abnormal ECM remodeling, and (4) discuss whether some PTMs are the cause or consequence of disease. New evidence clearly suggests that the ECM at some point in the pathogenesis becomes a driver of disease. These pathological modified ECM proteins may allow insights into complicated pathologies in which the end stage is excessive tissue remodeling, and provide unique and more pathology-specific biochemical markers.

The pathogenesis of osteoarthritis involves bone, cartilage and synovial inflammation: may estrogen be a magic bullet?

The female predominance of polyarticular osteoarthritis (OA), and in particular the marked increase of OA in women after the menopause points to a likely involvement of female sex hormones in the maintenance of cartilage homeostasis. This perception has inspired many research groups to investigate the role of estrogens in the modulation of cartilage homeostasis with the ultimate aim to clarify whether estrogen replacement therapy (ERT) could provide benefits in preventing the rapid rise in the prevalence of OA in postmenopausal women. The effects of ERT and selective estrogen-receptor modulators on the joint in various experimental models have been investigated. Clinically, the effects of estrogens have been evaluated by post hoc analysis in clinical trials using biochemical markers of cartilage and bone degradation. Lastly, the Women's Health Initiative trial (WHI) investigated the effects of estrogens on the joint and joint replacements. Even though the exact mode of action still needs to be elucidated, the effect involves both direct and indirect mechanisms on the whole joint pathophysiology. Several animal models have demonstrated structural benefits of estrogens, as well as significant effects on joint inflammation. This is in complete alignment with clinical data using biochemical markers of joint degradation which demonstrated approximately 50% inhibition of cartilage destruction. These finding were recently validated in WHI, where women taking estrogens had significantly less joint replacement. In conclusion, the pleiotropic effect of estrogens on several different tissues may match the complicated aetiology of OA in some important aspects.

Efficacy of intravenously administered ibandronate in postmenopausal Korean women with insufficient response to orally administered bisphosphonates

We investigated rates of insufficient and over-responsiveness to orally administered bisphosphonates in postmenopausal women, and tested the efficacy of intravenous ibandronate in patients with insufficient response to orally administered bisphosphonates. Postmenopausal women were treated with either alendronate (70 mg/week; n = 88) or risedronate (35 mg/week; n = 84) for 1 year, and their response to orally administered bisphosphonates was assessed using serum C-telopeptide (CTX) levels. Insufficient responders were changed to once-quarterly intravenous ibandronate 3 mg injection (n = 13) or maintained on orally administered bisphosphonates (n = 19), according to patients' preference, for an additional 1 year. There was no significant difference in baseline characteristics between two orally administered bisphosphonate groups except the bone mineral density values at the lumbar spine. Insufficient rate was higher in the risedronate group (19.0 %) than in the alendronate group (8.0 %), using the premenopausal serum CTX median as a cut-off (P = 0.043). The over-response rate among the alendronate group (59.1 %) was significantly higher than that in the risedronate group (38.1 %), based on a serum CTX cut-off value of 0.100 ng/ml (P = 0.006). Intravenous ibandronate suppressed serum CTX levels to a significantly greater degree at 7 days after the second dosing (0.191 ± 0.110 ng/mL; P < 0.001) and 3 months after the fourth dosing (0.274 ± 0.159 ng/mL; P = 0.004) among insufficient responders, compared with post-oral/pre-intravenous levels (0.450 ± 0.134 ng/mL). Rates of insufficient and over-responsiveness to orally administered bisphosphonates were considerable, and a change to intravenous bisphosphonates may be considered in patients showing an insufficient response to orally administered bisphosphonates.

Bone turnover markers: use in osteoporosis

Biochemical markers of bone turnover (bone turnover markers, BTMs) can be used to study changes in bone remodelling in osteoporosis. Investigators and clinicians should be aware of the appropriate sample collection and storage conditions for optimum measurements of these markers. Improvements in the variability of BTM measurements have resulted from the development of assays for automated analysers, and from international consensus regarding their use. Appropriate reference intervals should be used for the optimum interpretation of results. BTMs can provide information that is useful for the management of patients with osteoporosis, for both the initial clinical assessment and for guiding and monitoring of treatment. BTMs are clinically useful to determine possible causes of secondary osteoporosis by identifying patients with high bone turnover and rapid bone loss. In the follow-up of treatment response, BTM levels respond rapidly to both anabolic and antiresorptive treatments. BTM changes can also be used for understanding the mechanism of action of drugs in development and identifying the correct dose; they are also potentially useful as surrogate biomarkers for fracture.

The role of bone turnover markers in monitoring treatment in postmenopausal osteoporosis

Bone metabolism is assessed using biochemical bone turnover markers (BTM). BTM reflect the metabolic effect of drugs on bone turnover, help to establish the lowest dose inducing the largest change in the BTM, predict treatment-related reduction in fracture risk, and are helpful in bridging studies. Changes in BTM during anti-osteoporotic therapy depend on the cellular mechanism of action of the drug, degree of change in bone turnover rate and route of administration. BTM help to establish the optimal dose of anti-osteoporotic drugs because treatment-related changes in BTM are more rapid compared with change in BMD. A greater decrease in BTM levels during the first year of tantiresorptive treatment is associated with greater antifracture efficacy over 3 years. According to preliminary data, measurement of BTM can improve persistence with anti-resorptive treatment. The use of BTM to monitor anti-osteoporotic therapy in "real life" is limited at this stage.

Bisphosphonates in the treatment of osteoporosis: a review of their contribution and controversies

The bisphosphonates have revolutionized the therapy of osteoporosis, particularly the prevention of vertebral and hip fractures. The development of tools for defining absolute fracture risk facilitates their targeting to appropriate, at-risk individuals. Prescribers need to be aware of their common side effects (gastrointestinal intolerance with oral dosing and flu-like illness following intravenous use). Whether these agents carry a real risk of other problems such as osteonecrosis of the jaw and subtrochanteric fractures remains uncertain at the present time. If the association of these problems with bisphosphonates is real, it is important that the major therapeutic benefits that can accrue from bisphosphonates' appropriate targeted use are not lost as a result of the anxiety concerning these extremely rare adverse events.

Efficacy and safety of a once-yearly i.v. Infusion of zoledronic acid 5 mg versus a once-weekly 70-mg oral alendronate in the treatment of male osteoporosis: a randomized, multicenter, double-blind, active-controlled study

Zoledronic acid (ZOL) has shown beneficial effects on bone turnover and bone mineral density (BMD) in postmenopausal osteoporosis. This study compared the efficacy and safety of a once-yearly i.v. infusion of ZOL with weekly oral alendronate (ALN) in men with osteoporosis. In this multicenter, double-blind, active-controlled, parallel-group study, participants (n = 302) were randomized to receive either once-yearly ZOL 5 mg i.v. or weekly oral ALN 70 mg for 24 months. Changes in BMD and bone marker levels were assessed. ZOL increased BMD at the lumbar spine, total hip, femoral neck, and trochanter and was not inferior to ALN at 24 months [least squares mean estimates of the percentage increases in lumbar spine BMD of 6.1% and 6.2%; difference approximately 0.13; 95% confidence interval (CI) 1.12-0.85 in the ZOL and ALN groups, respectively]. At month 12, the median change from baseline of markers for bone resorption [serum β-C-terminal telopeptide of type I collagen (β-CTx) and urine N-terminal telopeptide of type I collagen (NTx)] and formation [serum N-terminal propeptide of type I collagen (P1NP) and serum bone-specific alkaline phosphatase (BSAP)] were comparable between ZOL and ALN groups. Most men preferred i.v. ZOL over oral ALN. The incidence of adverse events and serious adverse events was similar in the treatment groups. It is concluded that a once-yearly i.v. infusion of ZOL 5 mg increased bone density and decreased bone turnover markers similarly to once-weekly oral ALN 70 mg in men with low bone density.

New and emerging treatments for osteoporosis

A variety of new treatments for osteoporosis have become available within the last several years, and a number of emerging treatments remain in late clinical stage development. New and emerging treatments include more potent members, or more convenient formulations, of existing classes of therapy, but a number of the emerging treatments are first-generation compounds addressing specific therapeutic targets based on recent advances in understanding of basic bone biology. These new and emerging treatments include agents with anticatabolic effects, compounds with anabolic effects, and one agent possibly containing both anticatabolic and anabolic effects. The increasing variety of new and emerging treatments increases the possibility that effective therapy will be targeted to the specific needs of the individual patient.

The bone marker plot: an innovative method to assess bone turnover in women

BACKGROUND

Biochemical markers of bone turnover reflect the resorptive and reconstructive effects that act on the skeleton. Although elevated markers are commonly interpreted as a sign of an increased turnover rate, the balance between bone resorption and formation is mostly neglected. We introduce a graphic report combining both complementary processes.

MATERIALS AND METHODS

Bone turnover markers were measured in 599 women (aged 25-74 years). To set up reference ranges, 269 from 599 women were selected because of having T-scores > -1 and inconspicuous basic laboratory data. Concentrations of resorption and formation markers were mathematically transformed to build up plots with four fields, symbolizing fast and slow resorption and fast and slow formation processes. The reference data of bone turnover were represented by a 95% confidence ellipse. For individual marker plots, we converted data of bone turnover markers from therapy follow-up profiles of patients in a similar manner.

RESULTS

In pre-, peri- and postmenopausal women (n= 190, 39 +/- 6 years; n= 35, 51 +/- 6 years; n= 44, 55 +/- 5 years, respectively), the medians of the bone resorption marker CrossLaps and of the bone formation markers osteocalcin and aminoterminal propeptide of type I procollagen were 0.13/0.16/0.22 ng mL(-1), 21/21/25 ng mL(-1) and 36/35/45 ng mL(-1), respectively. In postmenopausal women, the marker plots revealed a shift towards accelerated bone resorption. A discrimination from osteopenic women (n= 138) failed.

CONCLUSION

The proposed marker plot facilitates the intuitive perception of bone turnover in individual patients as well as in patient groups by a synopsis of the balance between bone formation and resorption with the rate of these processes.

Biochemical markers of bone turnover: potential use in the investigation and management of postmenopausal osteoporosis

INTRODUCTION

The aim was to analyse data on the use of biochemical bone turnover markers (BTM) in postmenopausal osteoporosis.

METHODS

We carried out a comparative analysis of the most important papers concerning BTM in postmenopausal osteoporosis that have been published recently.

RESULTS

The BTM levels are influenced by several factors. They are moderately correlated with BMD and subsequent bone loss. Increased levels of bone resorption markers are associated with a higher risk of fracture. Changes in the BTM during the anti-osteoporotic treatment (including combination therapy) reflect the mechanisms of action of the drugs and help to establish their effective doses. Changes in the BTM during the anti-resorptive treatment are correlated with their anti-fracture efficacy.

CONCLUSION

Biological samples should be obtained in a standardised way. BTM cannot be used for prediction of the accelerated bone loss at the level of the individual. BTM help to detect postmenopausal women who are at high risk of fracture; however, adequate practical guidelines are lacking. BTM measurements taken during the anti-resorptive therapy help to identify non-compliers. They may improve adherence to the anti-resorptive therapy and the fall in the BTM levels that exceeds the predefined threshold improves patients' persistence with the treatment. There are no guidelines concerning the use of BTM in monitoring anti-osteoporotic therapy in postmenopausal women.

Tibolone inhibits bone resorption without secondary positive effects on cartilage degradation

Background

Osteoarthritis is associated with increased bone resorption and increased cartilage degradation in the subchondral bone and joint. The objective of the present study was to determine whether Tibolone, a synthetic steroid with estrogenic, androgenic, and progestogenic properties, would have similar dual actions on both bone and cartilage turnover, as reported previously with some SERMS and HRT.

Methods

This study was a secondary analysis of ninety-one healthy postmenopausal women aged 52–75 yrs entered a 2-yr double blind, randomized, placebo-controlled study of treatment with either 1.25 mg/day (n = 36), or 2.5 mg/day Tibolone (n = 35), or placebo (n = 20), (J Clin Endocrinol Metab. 1996 Jul;81(7):2419–22) Second void morning urine samples were collected at baseline, and at 3, 6, 12, and 24 months. Urine CrossLaps^® ELISA (CTX-I) and Urine CartiLaps^® ELISA (CTX-II) was investigated as markers of bone resorption and cartilage degradation, respectively.

Results

Tibolone significantly (P < 0.001) suppressed bone resorption by approximately 60%. In contrast, no effect was observed on cartilage degradation.

Conclusion

These data suggest uncoupling of the bone and cartilage effects of the synthetic steroid, Tibolone. Bone resorption was significantly decreased, whereas cartilage degradation was unchanged. These effects are in contrast to those observed some SERMs with effects on both bone and cartilage degradation. These effects may in part be described by the complicated pharmacology of Tibolone on testosterone, estrogen and progesterone receptors.

Considerations for development of surrogate endpoints for antifracture efficacy of new treatments in osteoporosis: a perspective

Because of the broad availability of efficacious osteoporosis therapies, conduct of placebo-controlled trials in subjects at high risk for fracture is becoming increasing difficult. Alternative trial designs include placebo-controlled trials in patients at low risk for fracture or active comparator studies, both of which would require enormous sample sizes and associated financial resources. Another more attractive alternative is to develop and validate surrogate endpoints for fracture. In this perspective, we review the concept of surrogate endpoints as it has been developed in other fields of medicine and discuss how it could be applied in clinical trials of osteoporosis. We outline a stepwise approach and possible study designs to qualify a biomarker as a surrogate endpoint in osteoporosis and review the existing data for several potential surrogate endpoints to assess their success in meeting the proposed criteria. Finally, we suggest a research agenda needed to advance the development of biomarkers as surrogate endpoints for fracture in osteoporosis trials. To ensure optimal development and best use of biomarkers to accelerate drug development, continuous dialog among the health professionals, industry, and regulators is of paramount importance.

Quarterly intravenous injection of ibandronate to treat osteoporosis in postmenopausal women

Osteoporosis is a chronic condition that generally requires long-term therapy for fracture risk reduction to become apparent. Although the bisphosphonates have made a major contribution to how clinicians manage osteoporosis, compliance with therapy has generally been less in the real-world setting than seen in clinical trials. Less-frequently administered dosage regimens or nonoral routes may enhance compliance and so maximize the therapeutic benefit of bisphosphonates. Ibandronate is a nitrogen-containing bisphosphonate, whose high potency allows it to be administered orally or intravenously with extended dosing intervals. This paper will review the role of intravenous ibandronate in the treatment of postmenopausal osteoporosis.

Emerging pharmacologic therapies for osteoporosis

Osteoporotic fractures are an important public health problem, contributing substantially to morbidity and mortality in an ageing world population and consuming considerable health resources. Presently available pharmacologic therapies for prevention of fragility fractures are limited in scope, efficacy and acceptability to patients. Considerable efforts are being made to develop new, more effective treatments for osteoporosis, and to refine/optimize existing therapies. These novel treatments include an expanding array of drugs that primarily inhibit osteoclastic bone resorption: estrogenic compounds, bisphosphonates, inhibitors of receptor activator of NF-kappaB ligand signaling, cathepsin K inhibitors, c-src kinase inhibitors, integrin inhibitors and chloride channel inhibitors. The advent of intermittent parathyroid hormone (PTH) therapy has provided proof-of-principle that osteoblast-targeted (anabolic) agents can effectively prevent osteoporotic fractures, and is likely to be followed by the introduction of other therapies based on PTH (orally active PTH analogs, antagonists of the calcium sensing receptor, PTH-related peptide analogs) and/or agents that induce osteoblast anabolism by means of pathways involving key, recently identified, molecular targets (wnt-low-density lipoprotein receptor-related protein 5 signaling, sclerostin and matrix extracellular phosphoglycoprotein).

Changes in bone remodelling and antifracture efficacy of intermittent bisphosphonate therapy: implications from clinical studies with ibandronate

Bisphosphonates reduce the rate of bone resorption and bone remodelling. Given daily, they decrease the risk of fractures in postmenopausal osteoporosis. When bisphosphonates were given at extended drug-free intervals this antifracture efficacy was generally not seen. This may be due to the different pattern of bone remodelling changes. Data from randomised clinical studies of ibandronate, given orally or intravenously, at different doses and for variable time intervals to women with osteoporosis were examined to explore the relationship between intermittent bisphosphonate therapy, changes in bone resorption and fracture risk. The magnitude of the reduction of the rate of bone resorption at the end of the drug-free interval rather than its fluctuation pattern after bisphosphonate administration determines antifracture efficacy, provided that these fluctuations occur within the premenopausal range. Prolongation of the drug-free interval beyond 2 weeks should be compensated by a dose higher than the cumulative daily dose.

Emerging issues with bisphosphonates

Bisphosphonates are the most commonly used agents in the management of metabolic bones diseases. Despite their established therapeutic value, a number of points of uncertainty remain, particularly in connection with their optimal long-term use. It is likely that definitive clinical trial data will not become available to resolve these questions, so careful clinical observation and caution are needed in patients who require treatment over periods of more than 10 years.

Ibandronate: once-monthly and intravenous dosing options for osteoporosis treatment

Ibandronate is a potent nitrogen-containing bisphosphonate that is currently available as a daily and once-monthly oral formulation for the treatment and prevention of osteoporosis. It has recently been approved for intermittent intravenous administration. The oral iBandronate Osteoporosis vertebral fracture trial in North America and Europe (BONE), Monthly Oral iBandronate In LadiEs (MOBILE), and Dosing IntraVenous Administration (DIVA) trials demonstrated that long-term daily and intermittent administration of ibandronate was efficacious for increasing bone mineral density and reducing markers of bone turnover. BONE demonstrated that ibandronate reduced the risk of new vertebral fractures and reduced the relative risk of nonvertebral fractures in higher-risk patients. Histomorphometric evaluations in the BONE and DIVA trials have demonstrated that bone quality is maintained following treatment. Giving patients the option of choosing their dose regimen and route of administration may increase overall adherence to treatment, leading to enhanced fracture protection in patients with osteoporosis.

Lack of hepatic metabolism of C-telopeptides of type I collagen

BACKGROUND

Bone biochemical markers have been used in dynamic studies of bone metabolism, and, for accurate interpretation of measured marker levels, it is essential to have information of extra-skeletal metabolism. Therefore, the objective of the present study was to investigate if the circulating C-telopeptides of type I collagen (CTX) was subject to hepatic extraction.

METHODS

Splanchnic plasma flow, total plasma volume and the plasma concentration of CTX was determined in an artery and the liver vein of eight healthy female volunteers. For comparison, the concentration of N-terminal propeptide of type I collagen, PINP, was measured.

RESULTS

No change in plasma level of CTX could be detected over the liver. In contrast, PINP decreased from an average of 52.9 ng/ml in the artery to 42.4 ng/ml in the vein, corresponding to a 19.8% reduction.

CONCLUSIONS

The C-telopeptides of type I collagen (CTX) are not subject to hepatic metabolism.

Effects of short-term alendronate on bone mineral density in haemodialysis patients

BACKGROUND

Low bone mineral density (BMD) is common in dialysis patients. Low BMD predicts the fracture risk in the general population. Bisphosphonate therapy improves BMD and lowers the fracture risk in many populations, but has not been tested in dialysis patients because of concerns about toxicity. In this investigation, the effect of a short course of alendronate on BMD in haemodialysis (HD) patients is evaluated.

METHODS

Thirty-one healthy HD patients were randomized to placebo versus 40 mg alendronate, taken once a week for 6 weeks. Hip and lumbar spine BMD were measured by dual energy X-ray absorptiometry at baseline and at 6 months. Osteocalcin, parathyroid hormone, calcium, phosphorous and alkaline phosphatase levels were assayed at baseline and at 1, 3 and 6 months.

RESULTS

The BMD and T-scores in specific regions of the hip were stable in the treatment group and decreased in the placebo group (P=0.05). The lumbar spine density increased minimally in both groups. In the treatment group, osteocalcin levels declined significantly at 1 month (P<0.05) and remained low. The main side-effect in the alendronate group was occurrence of gastroesophageal reflux symptoms in three subjects.

CONCLUSIONS

Low-dose alendronate, administered for a limited duration, appears to be well tolerated in dialysis patients. The BMD and T-scores declined at certain hip regions in the placebo group over 6 months, while remaining stable in the treatment group, suggesting a bone-preserving effect of alendronate. Further studies of longer duration, and including examination of bone histology, are needed to assess whether bisphosphonates can be used to preserve BMD in dialysis patients.

Emerging and potential therapies for osteoporosis

Osteoporotic fractures are an important public health problem, contributing substantially to morbidity and mortality in an ageing world population and consuming considerable health resources. Currently available pharmacological therapies for prevention of fragility fractures are limited in scope, efficacy and acceptability to patients. Considerable efforts are being made to develop new, more effective treatments for osteoporosis and to refine/optimise existing therapies. These novel treatments include an expanding array of drugs that primarily inhibit osteoclastic bone resorption; oestrogenic compounds, bisphosphonates, inhibitors of receptor activator of nuclear factor-kappaB ligand signalling, cathepsin K inhibitors, c-src kinase inhibitors, integrin inhibitors and chloride channel inhibitors. The advent of intermittent para-thyroid hormone (PTH) therapy has provided proof-of-principle that osteo-blast-targeted (anabolic) agents can effectively prevent osteoporotic fractures, and is likely to be followed by the introduction of other therapies based upon PTH, such as orally active PTH analogues, antagonists of the calcium sensing receptor, PTH-related peptide analogues, and/or agents that induce osteoblast anabolism via pathways involving key, recently identified, molecular targets (wnt low-density lipoprotein receptor-related protein-5 signalling, sclerostin and matrix extracellular phosphoglycoprotein).

Clinical Pharmacology of Potent New Bisphosphonates for Postmenopausal Osteoporosis

Bisphosphonates are potent inhibitors of bone resorption, used in most bone diseases associated with high bone resorption levels. Several bisphosphonates, developed to prevent and treat postmenopausal osteoporosis, increase bone mineral density and decrease biochemical markers of bone turnover, and more importantly, reduce fracture risk. Alendronate and risedronate have proven their efficacy to reduce vertebral and hip fracture risk among postmenopausal osteoporotic women, using daily regimens. Weekly intermittent schedules, however, are now most commonly prescribed, because they have shown pharmacologic equivalence to the daily regimen. Ibandronate has been the first bisphosphonate to demonstrate vertebral fracture risk reduction using an intermittent regimen. Studies using ibandronate as intravenous injections every 3 months are under way. Zoledronic acid may also be an attractive option for the treatment of postmenopausal osteoporosis if a large ongoing trial proves that a single annual injection of this compound allows osteoporotic fracture risk reduction.

Ibandronate: a clinical pharmacological and pharmacokinetic update

Ibandronate is a potent nitrogen-containing bisphosphonate. It has a strong affinity for bone mineral and potently inhibits osteoclast-mediated bone resorption. Ibandronate is effective for the treatment of hypercalcemia of malignancy, metastatic bone disease, postmenopausal osteoporosis, corticosteroid-induced osteoporosis, and Paget's disease. Oral ibandronate is rapidly absorbed (t(max) < 1 hour), with a low bioavailability (0.63%) that is further reduced (by up to 90%) in the presence of food. Ibandronate has a wide therapeutic index and is not metabolized and, therefore, has a low potential for drug interactions. Given its metabolic stability, ibandronate is eliminated from the blood by partitioning into bone (40%-50%) and through renal clearance (CL(R) approximately 60 mL/min). The CL(R) of ibandronate is linearly related to creatinine clearance. The sequestration of ibandronate in bone (V(D) > 90 L) results in a multiphasic elimination (t((1/2)) range approximately 10-60 hours), characterized by the slow release of ibandronate from the bone compartment. The potency of ibandronate and its sequestration into bone allow ibandronate to be developed as oral and intravenous injection formulations that can be administered with convenient extended between-dose intervals.

Efficacy and safety of ibandronate given by intravenous injection once every 3 months

Oral bisphosphonates are established therapeutics for postmenopausal osteoporosis. Alternative, simplified dosing regimens that improve tolerability and promote convenience may be advantageous. Ibandronate is a highly potent, nitrogen-containing bisphosphonate that can be administered as a convenient intravenous (i.v.) injection (over 15-30 s) in schedules featuring extended between-dose intervals. In a recent fracture prevention study, 1 and 0.5 mg i.v. ibandronate injections, given once every 3 months, were shown to dose-dependently increase lumbar spine and hip bone mineral density (BMD) and decrease biochemical markers of bone turnover in women with postmenopausal osteoporosis, but the overall magnitude of efficacy provided by both doses was suboptimal. In the present study (Intermittent Regimen intravenous Ibandronate Study: the IRIS study), the dose-response relationship with intermittent intravenous ibandronate injections was further evaluated in 520 postmenopausal osteoporotic women (aged 55-75 years, time since menopause >or= 5 years, lumbar spine [L1-L4] BMD T score < -2.5). At enrolment, participants were randomized to receive either 2 mg (n = 261) or 1 mg (n = 131) ibandronate or placebo (n = 128) intravenous injections, given once every 3 months. After 1 year, ibandronate therapy produced substantial and dose-dependent increases in lumbar spine and hip BMD, and decreases in biochemical markers of bone turnover, with the 2 mg dose providing significantly greater efficacy than the 1 mg dose. Most notably, lumbar spine BMD increased by 5.0% and 2.8% in the 2 and 1 mg groups, respectively, and decreased by 0.04% in the placebo group. Furthermore, total hip BMD increased by 2.9%, 2.2%, and 0.6%, respectively. Serum and urinary CTX, reflecting bone resorption, were decreased by 62.5% and 61%, respectively, with the 2 mg dose, and by 43.5% and 42%, respectively, with the 1 mg dose. Intravenous ibandronate was well tolerated with a similar incidence of adverse events to placebo. Importantly, no indicators of renal toxicity were reported. In summary, the 2 mg ibandronate regimen provides significantly greater BMD increases and significantly greater suppression of bone resorption markers than the 1 mg dose used in this study and in the previous fracture prevention study. Ongoing studies aim to further establish the efficacy and convenience of intermittent intravenous ibandronate injections in postmenopausal osteoporosis.

Intravenous bisphosphonate therapy for osteoporosis: where do we stand?

The use of oral bisphosphonates, particularly members of the aminobisphosphonate subclass, is well established for the treatment of osteoporosis. In a number of clinical settings, intravenous administration appears to be advantageous. However, current dosing and efficacy data are limited while definitive, long-term trials with some of these agents are ongoing. In this article, we review the available information and discuss the use of these drugs on that basis.