The effects of etidronate on trabecular bone remodeling in postmenopausal spinal osteoporosis: a randomized study comparing intermittent treatment and an ADFR regime

Etidronate for the primary and secondary prevention of osteoporotic fractures in postmenopausal women

BACKGROUND

Osteoporosis is an abnormal reduction in bone mass and bone deterioration, leading to increased fracture risk. Etidronate belongs to the bisphosphonate class of drugs which act to inhibit bone resorption by interfering with the activity of osteoclasts - bone cells that break down bone tissue. This is an update of a Cochrane review first published in 2008. For clinical relevance, we investigated etidronate's effects on postmenopausal women stratified by fracture risk (low versus high).

OBJECTIVES

To assess the benefits and harms of intermittent/cyclic etidronate in the primary and secondary prevention of osteoporotic fractures in postmenopausal women at lower and higher risk of fracture, respectively.

SEARCH METHODS

We searched the Cochrane Central Register of Control Trials (CENTRAL), MEDLINE, Embase, two clinical trial registers, the websites of drug approval agencies, and the bibliographies of relevant systematic reviews. We identified eligible trials published between 1966 and February 2023.

SELECTION CRITERIA

We included randomized controlled trials that assessed the benefits and harms of etidronate in the prevention of fractures for postmenopausal women. Women in the experimental arms must have received at least one year of etidronate, with or without other anti-osteoporotic drugs and concurrent calcium/vitamin D. Eligible comparators were placebo (i.e. no treatment; or calcium, vitamin D, or both) or another anti-osteoporotic drug. Major outcomes were clinical vertebral, non-vertebral, hip, and wrist fractures, withdrawals due to adverse events, and serious adverse events. We classified a study as secondary prevention if its population fulfilled one or more of the following hierarchical criteria: a diagnosis of osteoporosis, a history of vertebral fractures, a low bone mineral density T-score (≤ -2.5), or aged 75 years or older. If none of these criteria were met, we considered the study to be primary prevention.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. The review has three main comparisons: (1) etidronate 400 mg/day versus placebo; (2) etidronate 200 mg/day versus placebo; (3) etidronate at any dosage versus another anti-osteoporotic agent. We stratified the analyses for each comparison into primary and secondary prevention studies. For major outcomes in the placebo-controlled studies of etidronate 400 mg/day, we followed our original review by defining a greater than 15% relative change as clinically important. For all outcomes of interest, we extracted outcome measurements at the longest time point in the study.

MAIN RESULTS

Thirty studies met the review's eligibility criteria. Of these, 26 studies, with a total of 2770 women, reported data that we could extract and quantitatively synthesize. There were nine primary and 17 secondary prevention studies. We had concerns about at least one risk of bias domain in each study. None of the studies described appropriate methods for allocation concealment, although 27% described adequate methods of random sequence generation. We judged that only 8% of the studies avoided performance bias, and provided adequate descriptions of appropriate blinding methods. One-quarter of studies that reported efficacy outcomes were at high risk of attrition bias, whilst 23% of studies reporting safety outcomes were at high risk in this domain. The 30 included studies compared (1) etidronate 400 mg/day to placebo (13 studies: nine primary and four secondary prevention); (2) etidronate 200 mg/day to placebo (three studies, all secondary prevention); or (3) etidronate (both dosing regimens) to another anti-osteoporotic agent (14 studies: one primary and 13 secondary prevention). We discuss only the etidronate 400 mg/day versus placebo comparison here. For primary prevention, we collected moderate- to very low-certainty evidence from nine studies (one to four years in length) including 740 postmenopausal women at lower risk of fractures. Compared to placebo, etidronate 400 mg/day probably results in little to no difference in non-vertebral fractures (risk ratio (RR) 0.56, 95% confidence interval (CI) 0.20 to 1.61); absolute risk reduction (ARR) 4.8% fewer, 95% CI 8.9% fewer to 6.1% more) and serious adverse events (RR 0.90, 95% CI 0.52 to 1.54; ARR 1.1% fewer, 95% CI 4.9% fewer to 5.3% more), based on moderate-certainty evidence. Etidronate 400 mg/day may result in little to no difference in clinical vertebral fractures (RR 3.03, 95% CI 0.32 to 28.44; ARR 0.02% more, 95% CI 0% fewer to 0% more) and withdrawals due to adverse events (RR 1.41, 95% CI 0.81 to 2.47; ARR 2.3% more, 95% CI 1.1% fewer to 8.4% more), based on low-certainty evidence. We do not know the effect of etidronate on hip fractures because the evidence is very uncertain (RR not estimable based on very low-certainty evidence). Wrist fractures were not reported in the included studies. For secondary prevention, four studies (two to four years in length) including 667 postmenopausal women at higher risk of fractures provided the evidence. Compared to placebo, etidronate 400 mg/day may make little or no difference to non-vertebral fractures (RR 1.07, 95% CI 0.72 to 1.58; ARR 0.9% more, 95% CI 3.8% fewer to 8.1% more), based on low-certainty evidence. The evidence is very uncertain about etidronate's effects on hip fractures (RR 0.93, 95% CI 0.17 to 5.19; ARR 0.0% fewer, 95% CI 1.2% fewer to 6.3% more), wrist fractures (RR 0.90, 95% CI 0.13 to 6.04; ARR 0.0% fewer, 95% CI 2.5% fewer to 15.9% more), withdrawals due to adverse events (RR 1.09, 95% CI 0.54 to 2.18; ARR 0.4% more, 95% CI 1.9% fewer to 4.9% more), and serious adverse events (RR not estimable), compared to placebo. Clinical vertebral fractures were not reported in the included studies.

AUTHORS' CONCLUSIONS

This update echoes the key findings of our previous review that etidronate probably makes or may make little to no difference to vertebral and non-vertebral fractures for both primary and secondary prevention.

Current concepts in the management of bisphosphonate associated atypical femoral fractures

Bisphosphonates are a class of drugs used as the mainstay of treatment for osteoporosis. Bisphosphonates function by binding to hydroxyapatite, and subsequently targeting osteoclasts by altering their ability to resorb and remodel bone. Whilst aiming to reduce the risk of fragility fractures, bisphosphonates have been associated with atypical insufficiency fractures, specifically in the femur. Atypical femoral fractures occur distal to the lesser trochanter, until the supracondylar flare. There are a number of the differing clinical and radiological features between atypical femoral fractures and osteoporotic femoral fractures, indicating that there is a distinct difference in the respective underlying pathophysiology. At the point of presentation of an atypical femoral fracture, bisphosphonate should be discontinued. This is due to the proposed inhibition of osteoclasts and apoptosis, resulting in impaired callus healing. Conservative management consists primarily of cessation of bisphosphonate therapy and partial weightbearing activity. Nutritional deficiencies should be investigated and appropriately corrected, most notably dietary calcium and vitamin D. Currently there is no established treatment guidelines for either complete or incomplete fractures. There is agreement in the literature that nonoperative management of bisphosphonate-associated femoral fractures conveys poor outcomes. Currently, the favoured methods of surgical fixation are cephalomedullary nailing and plate fixation. Newer techniques advocate the use of both modalities as it gives the plate advantage of best reducing the fracture and compressing the lateral cortex, with the support of the intramedullary nail to stabilise an atypical fracture with increased ability to load-share, and a reduced bending moment across the fracture site. The evidence suggests that cephalomedullary nailing of the fracture has lower revision rates. However, it is important to appreciate that the anatomical location and patient factors may not always allow for this. Although causation between bisphosphonates and atypical fractures is yet to be demonstrated, there is a growing evidence base to suggest a higher incidence to atypical femoral fractures in patients who take bisphosphonates. As we encounter a growing co-morbid elderly population, the prevalence of this fracture-type will likely increase. Therefore, it is imperative clinicians continue to be attentive of atypical femoral fractures and treat them effectively.

Osteoporosis Treatments Affect Bone Matrix Maturation in a Rat Model of Induced Cortical Remodeling

To test how osteoporosis drugs affect bone matrix maturation during cortical bone remodeling, 72 pregnant rats were switched from a 0.4% to a 0.01% calcium diet at parturition for a 23‐day lactation period. At weaning, eight dams were sacrificed to establish baseline values, while the remaining dams were returned to 0.4% calcium and treated with vehicle (saline), sodium fluoride (NaF), zoledronic acid (ZA), or sclerostin antibody (Scl‐Ab) for either 7 or 28 days (eight animals per group per time point). Femora were examined by μCT, dynamic histomorphometry, Fourier transform infrared imaging, and three‐point bending of notched specimens. Cortical porosity decreased in all groups from baseline to day 28. Intracortical mineralizing surface (MS/BS) and mineral apposition rate (MAR), as well as the mineral‐to‐matrix ratio were unaffected by treatment, but intracortical crystallinity was increased in the ZA group at day 10 compared with vehicle. Cortical area increased in all groups over 28 days mainly because of an addition of bone at the endocortical surface. Endocortical MS/BS did not vary among the groups, but endocortical MAR was suppressed in the NaF group at day 2 and elevated in the Scl‐Ab group at day 4 compared with vehicle. Endocortical mineral‐to‐matrix ratio was increased at days 5 and 10 following NaF treatment and endocortical crystallinity was increased at day 5 following ZA treatment compared with vehicle. Fracture toughness did not differ among the groups. Thus, the treatments affected matrix maturation more strongly at the endocortical then intracortical envelope. In this model of induced remodeling, the bone formation phase is synchronized at multiple sites, facilitating study of the effects of drugs or other bone‐targeting agents on matrix maturation independent of their effects on the initiation of remodeling. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Use of Etidronate in the Treatment of Postmenopausal Osteoporosis

Objective:

To discuss the use of etidronate, a biphosphonate, in the treatment of women with postmenopausal osteoporosis and to determine its place in therapy when compared with conventional therapies.

Data Sources:

A MEDLINE search was conducted for clinical trials and review articles on biphosphonates in the treatment of osteoporosis.

Study Selection:

Six clinical trials and four review articles were selected because they dealt specifically with a biphosphonate in the treatment of postmenopausal osteoporosis.

Data Synthesis:

The studies provide a look at how the treatment evolved from continuous etidronate therapy to the more accepted intermittent cyclic therapy. The studies showed an increase in bone mass and a decrease in vertebral fractures in women receiving cyclic therapy with etidronate compared with those receiving placebo. In one study, however, a follow-up report one year later revealed that women taking etidronate experienced a 50 percent increase in vertebral fracture rate compared with those receiving placebo. This was a complete reversal from the data collected over the first two years of the study. This follow-up study is useful to point out a major potential concern associated with long-term use of etidronate—that etidronate therapy may cause mineralization defects, which could lead to alterations in bone integrity.

Conclusions:

Etidronate therapy has shown benefit in preserving bone in postmenopausal women. Comparative trials with conventional therapies such as estrogens have not been completed, which makes it difficult to determine etidronate's place in therapy. Long-term trials also are necessary to assess etidronate's potential to cause mineralization defects.

Actions of osteoporosis treatments on bone histomorphometric remodeling: a two-fold principal component analysis

This was the first study to apply principal component analysis method to bone histomorphometric parameters. The results corroborated teriparatide's distinct, yet different, mechanisms of action, which stimulate both bone formation and resorption.

INTRODUCTION

This study consolidated bone histomorphometric parameters and compared the effects of two osteoporosis treatments on bone remodeling by using a principal component analysis (PCA).

METHODS

Included in this analysis were postmenopausal women with osteoporosis who were treated with either teriparatide or alendronate and who completed transiliac bone biopsy at either 6 or 18 months in the randomized, double-blind Forteo Alendronate Comparator Trial. Eighteen histomorphometric parameters were grouped into formation and resorption categories. The first principal component of each category was estimated through the PCA. The summation of principal formation component (PFC) and principal resorption component (PRC) was calculated to represent the overall level of bone turnover. The difference between PFC and PRC was computed to determine the balance between formation and resorption.

RESULTS

The PFC was significantly higher in the teriparatide group than in the alendronate group (P < 0.0001), while the PRC was numerically lower in the alendronate group (P = 0.18). The mean difference between the PFC and PRC was positive in the teriparatide group and negative in the alendronate group.

CONCLUSIONS

Our approach of consolidating bone histomorphometric remodeling parameters corroborated the idea that the distinct, yet different, mechanisms of action of teriparatide treatment stimulate both bone formation and resorption, and alendronate treatment suppresses both bone formation and resorption.

Treatment of osteopenia

The majority of osteoporotic fractures happen in individuals with BMD t-scores in the osteopenic range (-2,5< t-score <-1). However, widespread use of anti-osteoporotic medication in this group based on t-score alone is not advisable because: 1) the number needed to treat is much higher (NNT>100) than in patients with fractured and t-score below -2,5 (NNT 10-20); 2)while specific osteoporosis treatments have demonstrated significant reductions of the fracture risk in patients with t-score <-2, 5, the efficacy in patients in the osteopenic range is less well established. Therefore, an osteopenic t-score does not in itself constitute a treatment imperative. Generally, osteopenia has to be associated with either low energy fracture(s) or very high risk for future fracture as assessed with risk calculators like FRAX to warrant specific osteoporosis therapy. Vertebral fractures are now conveniently assessed using lateral x-rays from DXA machines. In the vast majority of cases antiresorptive treatments (mainly hormone replacement therapy and SERMS in younger and bisphosphonates or Denosumab in older women) are the treatments of choice in this group of patients,-only rarely is anabolic therapy indicated.

Etidronate for the primary and secondary prevention of osteoporotic fractures in postmenopausal women

BACKGROUND

Osteoporosis is an abnormal reduction in bone mass and bone deterioration leading to increased fracture risk. Etidronate belongs to the bisphosphonate class of drugs which act to inhibit bone resorption by interfering with the activity of osteoclasts.

OBJECTIVES

To assess the efficacy of etidronate in the primary and secondary prevention of osteoporotic fractures in postmenopausal women.

SEARCH STRATEGY

We searched CENTRAL, MEDLINE and EMBASE for relevant randomized controlled trials published between 1966 to 2007.

SELECTION CRITERIA

Women receiving at least one year of etidronate for postmenopausal osteoporosis were compared to those receiving placebo and/or concurrent calcium/vitamin D. The outcome was fracture incidence.

DATA COLLECTION AND ANALYSIS

Study selection and data abstraction was done in duplicate. Meta-analysis of fracture outcomes was performed with data presented as relative risks and a relative change greater than 15% was considered clinically important. Study quality was assessed through the reporting of allocation concealment, blinding and withdrawals.

MAIN RESULTS

Eleven studies representing a total of 1248 patients were included in the review.A significant 41% relative risk reduction (RRR) in vertebral fractures across eight studies (RR 0.59, 95% CI 0.36 to 0.96) was found. The six secondary prevention trials demonstrated a significant RRR of 47% in vertebral fractures (RR 0.53, 95% CI 0.32 to 0.87) and a 5% absolute risk reduction (ARR); compared with the pooled result for the two primary prevention trials (RR 3.03, 95% CI 0.32 to 28.44), which was not significant. There were no statistically significant risk reductions for non-vertebral (RR 0.98, 95% CI 0.68 to 1.42), hip (RR 1.20, 95% CI 0.37 to 3.88) or wrist fractures (RR 0.87, 95% CI: 0.32 to 2.36). For adverse events, no statistically significant differences were found in the included studies. However, observational data has led to concerns regarding potential risk for upper gastrointestinal injury.

AUTHORS' CONCLUSIONS

Etidronate, at 400 mg per day, demonstrated a statistically significant and clinically important benefit in the secondary prevention of vertebral fractures. No statistically significant reductions in vertebral fractures were observed when it was used for primary prevention. In addition, no statistically significant reductions in non-vertebral, hip, or wrist fractures were found, regardless of whether etidronate was used for primary or secondary prevention. The level of evidence for all outcomes is Silver (www.cochranemsk.org.).

Effects of intravenous zoledronic acid once yearly on bone remodeling and bone structure

In a substudy of the HORIZON pivotal fracture trial, in which yearly intravenous zoledronic acid 5 mg was found to significantly reduce risk of various fracture types in patients with postmenopausal osteoporosis, 152 patients underwent bone biopsy. Zoledronic acid reduced bone turnover by 63% and preserved bone structure and volume, with evidence of ongoing bone remodeling in 99% of biopsies obtained.

INTRODUCTION

In the HORIZON pivotal fracture trial (PFT), enrolling 7,736 women with postmenopausal osteoporosis, three annual intravenous infusions of the bisphosphonate zoledronic acid (5 mg) significantly reduced morphometric vertebral, clinical vertebral, hip, and nonvertebral fractures by 70%, 77%, 41%, and 25%, respectively. Whereas 79% of patients received zoledronic acid/placebo only (stratum I, n = 6,113), 21% received concomitant treatment with other antiresorptive drugs, excluding other bisphosphonates, PTH, and strontium (stratum II, n = 1,652).

MATERIALS AND METHODS

To determine effects on bone remodeling and bone architecture, iliac crest bone biopsies were obtained in 152 patients on active treatment or placebo at 3 yr after double tetracycline labeling. In five patients, only qualitative histology was performed, leaving 147 biopsy cores (79 on active treatment and 68 on placebo) for microCT analysis and histomorphometry.

RESULTS

Analysis of bone structure by microCT revealed higher trabecular bone volume (BV/TV) in the zoledronic acid group (median, 16.6% versus 12.8%; p = 0.020). In addition, patients treated with zoledronic acid exhibited higher trabecular numbers (p = 0.008), decreased trabecular separation (p = 0.011), and a trend toward improvement in connectivity density (p = 0.062), all indicating better preservation of trabecular structure after treatment with zoledronic acid. Qualitative analysis revealed presence of tetracycline label in 81 of 82 biopsies from patients on zoledronic acid and all 70 biopsies from placebo patients, indicative of continued bone remodeling. No bone pathology was observed. Zoledronic acid induced a 63% median (71% mean) reduction of the activation frequency (Ac.f; p < 0.0001) and reduced mineralizing surface (MS/BS; p < 0.0001) and volume referent bone formation rate (BFR/BV) versus placebo, indicating reduced bone turnover. Mineral appositional rate was higher in the zoledronic acid group (p = 0.0002), suggesting improved osteoblast function compared with placebo. Mineralization lag time was similar in the two groups, whereas osteoid volume (OV/BV; p < 0.0001) and osteoid thickness (O.Th; p = 0.0094) were lower in zoledronic acid-treated patients, indicating normal osteoid formation and mineralization of newly formed bone. Concomitant administration of other antiresorptive osteoporosis therapies (e.g., raloxifene, tamoxifen, tibolone, ipriflavone) did not significantly alter the tissue level response to zoledronic acid.

CONCLUSIONS

Annual dosing for 3 yr with zoledronic acid 5 mg intravenously resulted in a median 63% (mean, 71%) reduction of bone turnover and preservation of bone structure and mass without any signs of adynamic bone. Concomitant treatment with other osteoporosis therapies did not significantly affect the bone response to zoledronic acid.

WITHDRAWN: Etidronate for treating and preventing postmenopausal osteoporosis

BACKGROUND

Osteoporosis is a clinical syndrome of reduced bone mass and increased fracture susceptibility. There are now a number of options, including etidronate which can decrease the risk of fractures.

OBJECTIVES

To systematically review the efficacy of etidronate on bone density, fractures and toxicity in postmenopausal women.

SEARCH STRATEGY

We searched MEDLINE from 1966 to December 1998, examined citations of relevant articles, and the proceedings of international osteoporosis meetings. We contacted osteoporosis investigators to identify additional studies, primary authors, and pharmaceutical industry sources for unpublished data.

SELECTION CRITERIA

We included thirteen trials (with 1010 participants) that randomized women to etidronate or an alternative (placebo or calcium and/or vitamin D) and measured bone density for at least one year.

DATA COLLECTION AND ANALYSIS

For each trial, three independent reviewers assessed the methodological quality and abstracted data.

MAIN RESULTS

The data suggested a reduction in vertebral fractures with a pooled relative risk of 0.60% (95% CI 0.41 to 0.88). There was no effect on non-vertebral fractures (pooled relative risk 1.00, (95% CI 0.68 to 1.42)). Etidronate, relative to control, increased bone density after three years of treatment in the lumbar spine by 4.27% (95% CI 2.66 to 5.88), in the femoral neck by 2.19% (95% CI 0.43, 3.95) and in the total body by 0.97% (95% CI 0.39, 1.55). Effects were larger at 4 years, though the number of patients followed was much smaller.

AUTHORS' CONCLUSIONS

Etidronate increases bone density in the lumbar spine and femoral neck. The pooled estimates of fracture reduction with etidronate are consistent with a reduction in vertebral fractures, but no effect on non-vertebral fractures.

Osteoporosis: how should it be treated?

Osteoporosis develops as a result of imbalance between bone resorption and bone formation. A number of effective and safe therapies for osteoporosis are currently available, most of which are inhibitors of bone resorption. However, because osteoporosis is a complex and heterogeneous disease with different pathogenetic factors, defining the role of the different factors in its development is important in formulating a more selective approach to therapy. This review discusses the advantages and disadvantages of the currently available agents used in the management of osteoporosis.

The effect of alendronate sodium on spinal fusion: a rabbit model

BACKGROUND CONTEXT

Bisphosphonates affect bone remodeling and increase bone mass through the inhibition of osteoclasts. Their effect on osteoblasts, and the balance between osteoblastic and osteoclastic activity on bone turnover and healing, is not completely understood. Specifically, the effect of bisphosphonates on spinal fusion has yet to be determined. With the increasing use of bisphosphonates in the elderly population, this effect needs to be delineated.

PURPOSE

To evaluate the effect of alendronate sodium after an intertransverse process spinal fusion in a rabbit model.

STUDY DESIGN/SETTING

Randomized double-blinded in vivo study of the effect of alendronate sodium in a spinal fusion model.

METHODS

Fifty New Zealand white rabbits underwent a posterolateral L5-L6 intertransverse process arthrodesis with autogenous iliac crest bone graft. The rabbits were then randomly divided into two groups. Group I received 3 cc of saline placebo per oral gavage, and Group II received 200 micrograms (approximately 0.05 mg/kg/day) of alendronate sodium dissolved in 3 cc of saline per day for 8 weeks. Upon completion, the rabbits were sacrificed and the lumbar spines harvested, radiographed and graded for motion across the fusion site with manual palpation. Two independent pathologists then prepared and sectioned each left and right fusion mass. Three random x10 fields were examined and graded for both the cephalad and caudad ends of each section (516 fields). Fusion quality was graded using an established histological scoring scale (score 0 to 7 based on fibrous and bone content of the fusion mass).

RESULTS

Two rabbits died on the day of operation, and 48 rabbits survived the operation. Five additional rabbits died within the first 2 postoperative weeks. Thus, 43 rabbits (21 in Group I, 22 in Group II) completed the 8-week course of treatment. Grading each side separately, 26 of 42 fusion masses (62%) in Group I and 24 of 44 fusion masses (55%) in Group II had radiographic evidence of fusion (p=.76). With gross palpation, 11 of 21 motion segments (52%) in Group I versus 13 of 22 motion segments (59%) in Group II were determined to have a solid fusion (p=.76). Histologically, Group I had a higher median score (6.0; range, 0 to 7 vs. 1.0; range, 0 to 7; p<.0001) and a higher fusion rate (76% vs. 45%; p=.004) than Group II.

CONCLUSIONS

Alendronate sodium appears to inhibit or delay bone fusion in a rabbit model. Presumably, this occurs as a result of uncoupling the balanced osteoclastic and osteoblastic activity inherent to bone healing. These findings suggest that a discontinuance of alendronate sodium postoperatively during the acute fusion period may be warranted.

Effect of menatetrenone on bone mineral density and incidence of vertebral fractures in postmenopausal women with osteoporosis: a comparison with the effect of etidronate

The purpose of the present study was to compare the effects of etidronate and menatetrenone on bone mineral density (BMD) and the incidence of vertebral fractures in postmenopausal women with osteoporosis. Seventy-two osteoporotic women, more than 5 years after menopause, 53-78 years of age, were randomly divided into three administration groups: E group; intermittent cyclical etidronate (200 mg/day, 14 days per 3 months; n = 25); M group; menatetrenone (45 mg/day, daily; n = 23); and C group (control); calcium lactate (2 g/day, daily; n = 24). Forearm BMD was measured by dual-energy X-ray absorptiometry at 0, 6, 12, 18, and 24 months after the treatment started. There were no significant differences in age, body mass index, years since menopause, and initial BMD among the three groups. One-way analysis of variance (ANOVA) with repeated measurements showed a significant decrease in BMD in the C group (P < 0.0001). Two-way ANOVA with repeated measurements showed a significant increase in BMD in the M group compared with that in the C group (P < 0.0001), and a significant increase in BMD in the E group compared with that in the C and M groups (P < 0.0001 and P < 0.01, respectively). The indices of new vertebral fractures/1000 patient-years in the E and M groups were significantly higher than that in the C group (chi(2) = 47.7; P < 0.0001 and chi(2) = 42.4; P < 0.0001, respectively), and did not differ significantly between the E and M groups. The present preliminary study provides evidence to suggest that, despite the lower increase in BMD produced by menatetrenone, this agent, as well as etidronate, may have the potential to reduce osteoporotic vertebral fractures in postmenopausal women with osteoporosis.

Potent and selective inhibition of human cathepsin K leads to inhibition of bone resorption in vivo in a nonhuman primate

Cathepsin K is a cysteine protease that plays an essential role in osteoclast-mediated degradation of the organic matrix of bone. Knockout of the enzyme in mice, as well as lack of functional enzyme in the human condition pycnodysostosis, results in osteopetrosis. These results suggests that inhibition of the human enzyme may provide protection from bone loss in states of elevated bone turnover, such as postmenopausal osteoporosis. To test this theory, we have produced a small molecule inhibitor of human cathepsin K, SB-357114, that potently and selectively inhibits this enzyme (Ki = 0.16 nM). This compound potently inhibited cathepsin activity in situ, in human osteoclasts (inhibitor concentration [IC]50 = 70 nM) as well as bone resorption mediated by human osteoclasts in vitro (IC50 = 29 nM). Using SB-357114, we evaluated the effect of inhibition of cathepsin K on bone resorption in vivo using a nonhuman primate model of postmenopausal bone loss in which the active form of cathepsin K is identical to the human orthologue. A gonadotropin-releasing hormone agonist (GnRHa) was used to render cynomolgus monkeys estrogen deficient, which led to an increase in bone turnover. Treatment with SB-357114 (12 mg/kg subcutaneously) resulted in a significant reduction in serum markers of bone resorption relative to untreated controls. The effect was observed 1.5 h after the first dose and was maintained for 24 h. After 5 days of dosing, the reductions in N-terminal telopeptides (NTx) and C-terminal telopeptides (CTx) of type I collagen were 61% and 67%, respectively. A decrease in serum osteocalcin of 22% was also observed. These data show that inhibition of cathepsin K results in a significant reduction of bone resorption in vivo and provide further evidence that this may be a viable approach to the treatment of postmenopausal osteoporosis.

Effects of high-dose etidronate treatment on microdamage accumulation and biomechanical properties in beagle bone before occurrence of spontaneous fractures

We recently demonstrated that suppressed bone remodeling allows microdamage to accumulate and causes reductions in some mechanical properties. However, in our previous study, 1 year treatment with high-dose etidronate (EHDP) did not increase microdamage accumulation in most skeletal sites of dogs in spite of complete remodeling suppression and the occurrence of spontaneous fractures of ribs and/or thoracic spinous processes. This study evaluates the effects of EHDP on microdamage accumulation and biomechanical properties before fractures occur. Thirty-six female beagles, 1-2 years old, were treated daily for 7 months with subcutaneous injections of saline vehicle (CNT) or EHDP at 0.5 (E-low) or 5 mg/kg per day (E-high). After killing, bone mineral measurement, histomorphometry, microdamage analysis, and biomechanical testing were performed. EHDP treatment suppressed intracortical and trabecular remodeling by 60%-75% at the lower dose, and by 100% at the higher dose. Osteoid accumulation caused by a mineralization deficit occurred only in the E-high group, and this led to a reduction of mineralized bone mass. Microdamage accumulation increased significantly by two- to fivefold in the rib, lumbar vertebra, ilium, and thoracic spinous process in E-low, and by twofold in the lumbar vertebra and ilium in E-high. However, no significant increase in damage accumulation was observed in ribs or thoracic spinous processes in E-high where fractures occur following 12 months of treatment. Mechanical properties of lumbar vertebrae and thoracic spinous processes were reduced significantly in both E-low and E-high. These findings suggest that suppression of bone remodeling by EHDP allows microdamage accumulation, but that osteoid accumulation reduces production of microdamage.

Histomorphometric assessment of bone turnover in uraemic patients: comparison between activation frequency and bone formation rate

AIMS

The histomorphometric assessment of bone formation rate (BFR/BS) in bone biopsies from uraemic patients is of crucial importance in differentiating low from high turnover types of renal osteodystrophy. However, since BFR/BS relies on osteoblasts, activation frequency (Ac.f), encompassing all remodelling phases, has recently been preferred to BFR/BS. This study was carried out to consider whether estimation of Ac.f is superior, in practical terms, to that of BFR/BS in distinguishing between different rates of bone turnover in uraemic patients.

METHODS AND RESULTS

Bone biopsies from 27 patients in predialysis (20 men and seven women; mean age 53 +/- 12 years) and 37 in haemodialysis (22 men and 15 women; mean age 53 +/- 12 years) were examined. The types of renal osteodystrophy were classified on the basis of morphology. Bone formation rate and Ac.f were evaluated according to standardized procedures. The Ac.f was calculated both as a ratio between BFR/BS and wall thickness (W.Th) and as a reciprocal of erosion, formation and quiescent periods (EP, FP and QP). Patients were affected by renal osteodystrophy with predominant hyperparathyroidism (two predialysis and 16 dialysis), predominant osteomalacia (three predialysis and seven dialysis) or that of advanced (nine predialysis and five dialysis) or mild (seven predialysis and four dialysis) mixed type or adynamic type (six predialysis and five dialysis). Activation frequency, which with either formula requires the measurement of W.Th, i.e. the thickness of bone structural units (BSUs), was not calculated in three dialysis patients with severe hyperparathyroidism and in one predialysis and four dialysis patients with severe osteomalacia, because only incomplete BSUs were found. In dialysis, EP was higher in the adynamic than in the other types of osteodystrophy. During both predialysis and dialysis, FP was higher in osteomalacia than in the other forms of osteodystrophy, and in adynamic osteopathy than in hyperparathyroidism or in advanced and mild mixed osteodystrophy. During predialysis and dialysis, QP was higher in the adynamic than in the other forms of osteodystrophy. Correlations were found between BFR/BS and Ac.f, during predialysis (r=0.97) and dialysis (r=0.95).

CONCLUSIONS

The superiority of Ac.f in assessing bone turnover, in comparison to BFR/BS, is conceptual rather than practical. The highest values for FP in osteomalacia and for QP in adynamic bone allow a clearer characterization of these low turnover conditions.

How many patients are needed? Variation and design considerations in bone histomorphometry

In osteoporosis research, bone histomorphometry plays an important role in documenting the biological effects and possible side-effects of new drug treatments. To ensure that the study is properly scaled, it is important to be concerned with the risk of type II error; that is, the risk of failing to detect a real difference. We therefore calculated the necessary sample size in bone histomorphometric studies according to a specified difference of 15% between two groups. The calculations were based on variance components estimated from three different studies: women with a distal fracture of the forearm (n = 22); patients with pituitary insufficiency (n = 21); and patients with primary hyperparathyroidism (n = 21). Using a significance level of 0.05 and a risk of type II error of 0.20, the statistical power of two different designs was compared: a single biopsy design comparing the responses in two groups after the treatment; and a paired biopsy design in which individual differences (posttreatment minus baseline) were calculated before the comparison of the two groups. We found that the mineral apposition rate, wall thickness, and erosion depth are statistically powerful indices that, in the single biopsy design, require no more than n = 25 in each group to detect differences of 15% between the groups. Bone volume, erosion surface, osteoid surface, mineralizing surface, and activation frequency need group sizes of 100-600 individuals to find a 15% difference to be statistically significant. However, the effect of bisphosphonate treatment, for instance, is large enough to reduce the group size to 20 individuals concerning activation frequency. The remodeling balance reaches extreme group sizes of several thousand for a 15% difference to be statistically significant, but for a 5 microm (approximately 150%) improvement, about 100 individuals are required in the single biopsy design. An analysis of the components of variance showed that the variation between individuals is small and often negligible compared with the variation within individuals, and sample sizes needed for the paired biopsy design are therefore larger than those for the single biopsy design. In conclusion, the most cost-effective histomorphometric study design within a randomized clinical trial appears to be a single biopsy design comparing posttreatment biopsies with scaling performed according to the statistical power of the indices of interest.

Treatment of osteoporosis with bisphosphonates

Bisphosphonates are safe and effective agents for treatment and prevention of osteoporosis. Alendronate and risedronate are the best studied of all agents for osteoporosis in terms of efficacy and safety. They increase bone mass. In patients who have established osteoporosis, they reduce the risk of vertebral fractures. They are the only agents shown in prospective trials to reduce the risk of hip fractures and other nonvertebral fractures. They are approved by the US FDA for prevention of bone loss in recently menopausal women, for treatment of postmenopausal osteoporosis, and for management of glucocorticoid-induced bone loss. Other bisphosphonates (e.g., etidronate for oral use, pamidronate for intravenous infusion) are also available and can be used off-label for patients who cannot tolerate approved agents. Bisphosphonates combined with estrogen produce greater gains in bone mass compared with either agent used alone; whether there is a greater benefit of combination therapy on fracture risk is not clear. Combining a bisphosphonate with raloxifene or calcitonin is probably safe, although data on effectiveness are lacking.

Suppressed bone turnover by bisphosphonates increases microdamage accumulation and reduces some biomechanical properties in dog rib

It has been hypothesized that suppression of bone remodeling allows microdamage to accumulate, leading to increased bone fragility. This study evaluated the effects of reduced bone turnover produced by bisphosphonates on microdamage accumulation and biomechanical properties of cortical bone in the dog rib. Thirty-six female beagles, 1-2 years old, were divided into three groups. The control group (CNT) was treated daily for 12 months with saline vehicle. The remaining two groups were treated daily with risedronate (RIS) at a dose of 0.5 mg/kg per day or alendronate (ALN) at 1.0 mg/kg per day orally. After sacrifice, the right ninth rib was assigned to cortical histomorphometry or microdamage analysis. The left ninth rib was tested to failure in three-point bending. Total cross-sectional bone area was significantly increased in both RIS and ALN compared with CNT, whereas cortical area did not differ significantly among groups. One-year treatment with RIS or ALN significantly suppressed intracortical remodeling (RIS, 53%; ALN, 68%) without impairment of mineralization and significantly increased microdamage accumulation in both RIS (155%) and ALN (322%) compared with CNT. Although bone strength and stiffness were not significantly affected by the treatments, bone toughness declined significantly in ALN (20%). Regression analysis showed a significant nonlinear relationship between suppressed intracortical bone remodeling and microdamage accumulation as well as a significant linear relationship between microdamage accumulation and reduced toughness. This study showed that suppression of bone turnover by high doses of bisphosphonates is associated with microdamage accumulation and reduced some mechanical properties of bone.

Etridronate therapy in the treatment and prevention of osteoporosis

Etidronate disodium is an oral bisphosphonate compound known to reduce bone resorption through the inhibition of osteoclastic activity. This article is a review of its efficacy and safety in the treatment and prevention of postmenopausal and corticosteroid-induced osteoporosis. In general, studies of cyclical etidronate therapy (400 mg daily for 2 wk every 3 mo) have found a significant improvement in bone density. These studies have not been powered to study fracture incidence, but a reduced fracture rate has been found in some of the studies reviewed. Studies examining cyclical etidronate in the prevention of osteoporosis indicate it prevents early menopausal bone loss and is free of significant side effects. In both prevention of corticosteroid-induced osteoporosis and treatment of patients who have been on long-term corticosteroid therapy, cyclical etidronate appears to increase bone density and prevent further loss of bone. In summary, a review of available literature pertaining to the use of etidronate in prevention and treatment of primary and secondary osteoporosis has been presented. This review suggests etidronate, used as a cyclical therapy, is a safe and effective therapy. The weight of evidence suggests it is capable of reducing fracture risk in patients with osteoporosis. Increases in bone density at the spine and hip are not as pronounced as with some other bisphosphonates, particularly alendronate, but no direct clinical comparison trials of significant size or duration have been undertaken.

Etidronate and alendronate in the treatment of postmenopausal osteoporosis

OBJECTIVE

To review the clinical trials evaluating the efficacy of etidronate and alendronate in the treatment of established postmenopausal osteoporosis.

DATA SOURCE

A MEDLINE search was performed (from 1966 through September 1998) using the search terms bisphosphonates, etidronate, alendronate, and postmenopausal osteoporosis. English-language articles were considered for review.

STUDY SELECTION AND DATA EXTRACTION

Prospective, randomized, double-blind, placebo-controlled clinical trials using fracture as an end point were selected to review the efficacy of etidronate and alendronate in the treatment of postmenopausal osteoporosis. Results for the outcomes of bone mineral density (BMD) and fracture are summarized.

DATA SYNTHESIS

Etidronate and alendronate increase spinal BMD in postmenopausal women with osteoporosis. In one study, etidronate decreased the number of women sustaining new radiographic vertebral fractures over two years, but this effect was lost after three years of treatment. Alendronate reduces the number of radiographic vertebral fractures in postmenopausal women with a low bone mass. In women with preexisting fractures, alendronate decreases the number of patients with radiographic vertebral fractures, clinical (i.e., symptomatic vertebral and nonvertebral) fractures, and hip fractures. A significant reduction in the overall number of nonvertebral fractures has not been demonstrated in clinical trials evaluating either alendronate or etidronate.

CONCLUSIONS

No studies have directly compared the efficacy of alendronate and etidronate and the results of long-term clinical trials (i.e., >5 y) have not been published. Based on the results obtained in clinical trials using fracture as an end point, alendronate appears to be the bisphosphonate of choice. Safety profiles and cost should also be considered in the choice of etidronate or alendronate for the treatment of postmenopausal osteoporosis.

Morphometric evidence that YM175, a bisphosphonate, reduces trabecular bone resorption in ovariectomized dogs with dietary calcium restriction

We examined mechanisms by which incadronate disodium (YM175) prevented bone resorption in ovariectomized dogs with dietary calcium restriction using the morphometrical method. YM175 (0.01-1.0 mg/kg) was given to ovariectomized dogs for 18 months. Because lumbar bone mineral density remained constant at month 17, we assumed that the trabecular bone resorption rate was equal to the bone formation rate and that wall thickness equaled resorption cavity depth. YM175 decreased both the bone resorption rate per number of osteoclasts and resorption cavity depth of cancellous pockets which were increased in ovariectomized dogs. These results suggest that YM175 reduces bone loss by decreasing the resorbing activity of osteoclasts.

Bisphosphonates and osteoporosis treatment in Italy

A treatment against osteoporosis can be considered efficacious only when its beneficial effects on bone remodeling, bone mass, and osteoporotic fracture incidence are proven. As for any treatment, proven efficacy must be combined with proven safety. This review analyzes published data on efficacy and safety of alendronate, clodronate and etidronate, the bisphosphonates currently marketed in Italy for osteoporosis treatment. Different studies have shown that alendronate, clodronate and etidronate reduce bone turnover, and increase bone mineral density in postmenopausal osteoporotic patients. Prospective, double blind, multicenter studies reported a reduction in osteoporotic fracture incidence for alendronate and etidronate. Fracture incidence reduction by clodronate, on the other hand, was shown only in an open label study. Finally, a reduction in fracture incidence by etidronate was shown in a large retrospective postmarketing study. Postmarketing surveillance evidenced that osteomalacia, a suspected side effect of etidronate treatment, does not occur at the currently used dose regimens. Postmarketing surveillance of alendronate has recently raised some concern regarding possible severe esophageal damage during alendronate treatment, especially when the drug is not taken according to the manufacturer's instructions.

Treatment of osteoporosis with bisphosphonates

Several bisphosphonates are effective for preventing bone loss associated with estrogen deficiency, glucocorticoid treatment, and immobilization, and for at least partially reversing bone loss in patients with postmenopausal osteoporosis and steroid-induced osteoporosis. The most promising of these agents are etidronate, alendronate, risedronate, and ibandronate. These drugs should have an important role in the prevention and treatment of osteoporosis; however, more research is needed regarding optimal doses and regimens (continuous versus intermittent, oral versus parenteral), comparisons with other agents, and their use in combination with other agents.

Calcitonin versus etidronate for the treatment of postmenopausal osteoporosis: a meta-analysis of published clinical trials

This review examines the evidence on the efficacy of calcitonin and etidronate in the prevention of osteoporosis and osteoporotic fractures. MEDLINE was searched for clinical trials calcitonin or etidronate and reviews of the treatment of postmenopausal osteoporosis. The reference sections of the papers retrieved were again searched for trials on the treatments of interest. Two people independently collected data from the trials that met the inclusion criteria of the study. Weighted means in the change in bone mineral density (BMD) and differences in vertebral fracture rates were computed for calcitonin and etidronate separately. The existence of publication bias was investigated by funnel plots of effect size against sample size. Eighteen clinical trials and calcitonin and six with etidronate were included in the meta-analysis. The pooled change in vertebral BMD at the end of the studies was 1.97 (95% CI 1.77 to 2.17) with calcitonin and 3.20 (95% CI 2.92 to 3.48) with etidronate. Pooled change in proximal femur BMD was 0.32 (95% CI -0.27 to 0.91) with calcitonin and 2.42 (95% CI 2.16 to 2.68) with etidronate. The aggregated number of vertebral fractures prevented by the treatment was 59.2 per 1000 patient-years (95% CI 55.1 to 63.3) for calcitonin and 28.3 (95% CI 26.2 to 30.4) for etidronate. With the available evidence we cannot establish the superiority of either of the two drugs for the treatment of postmenopausal osteoporosis. The clinical trials are particularly lacking in data on hip fracture, the most important consequence of osteoporosis. In this situation consideration of the relative costs of the drugs is prominent.

A randomized, placebo-controlled study on the effect of cyclic intermittent etidronate therapy on the bone mineral density changes associated with six months of gonadotropin-releasing hormone agonist treatment

OBJECTIVE

Our purpose was to determine whether intermittent cyclic etidronate therapy blocks the decline in bone density associated with gonadotropin-releasing hormone agonist therapy.

STUDY DESIGN

Thirty-one premenopausal subjects who needed treatment with leuprolide (Lupron) 3.75 mg monthly for 6 months were randomized to etidronate or placebo. Bone turnover was assessed by measurement of serum calcium, phosphorus, alkaline phosphatase, and fasting urinary calcium/creatinine ratios. Bone density was measured by dual energy x-ray absorptiometry.

RESULTS

Gonadotropin-releasing hormone treatment produced a significant decrease (4% to 10%) in bone density at the anteroposterior and lateral spine in placebo-treated patients (11). No significant change was demonstrated in etidronate-treated patients (15). Significant increases in serum calcium, phosphorus, alkaline phosphatase, and urinary calcium/creatinine ratios were noted in the placebo group. No significant change in these parameters were evident in the etidronate group.

CONCLUSION

Etidronate blocks bone mineral density changes associated with gonadotropin-releasing hormone agonist therapy and normalizes serum and urine indicators of bone turnover.

The effects of risedronate on canine cancellous bone remodeling: three-dimensional kinetic reconstruction of the remodeling site

To investigate the dose-dependent effects of risedronate on cancellous bone remodeling, adult female beagle dogs were treated with either placebo, 0.1, 0.5, or 2.5 mg/kg/day of risedronate orally in an intermittent cyclic regimen (7 days on 21 days off), repeated three times. Iliac cancellous bone samples were subjected to histomorphometric analysis and three-dimensional (3-D) kinetic reconstruction of the remodeling site was performed. In the 0.1 mg/kg dose group, resorption and activation indices were no different from the placebo group. However, wall thickness was increased resulting in a positive bone balance at the level of the remodeling unit. In the 0.5 and 2.5 mg/kg dose groups, a dose-dependent reduction in activation frequency and tissue level bone formation was observed. Resorption rates were also significantly decreased, 60% and 80% for the 0.5- and 2.5-mg/kg groups, respectively. An approximate 25% reduction in final erosion depth was noted in both these groups. Analyses of the growth curves of the bone packet confirmed that the kinetics of the growth of a completed packet were different in the 0.5- and 2.5-mg/kg dose groups compared with placebo. These changes were associated with a significant increase in the final wall thickness in both groups indicating no net impairment of osteoblast function. These increases in wall thickness in combination with the reductions in final erosion depth in the 0.5 and 2.5 mg/kg groups resulted in a significant dose-dependent positive bone balance. This pharmacological profile suggests that risedronate may be of therapeutic utility in the treatment of metabolic bone diseases where reductions in activation frequency and resorptive cell activity at the level of the remodeling unit are a therapeutic goal.

Rationale for the use of alendronate in osteoporosis

Bisphosphonates are being used in disorders associated with accelerated resorption of bone, particularly Paget's disease of bone and the bone disease of malignancy. Their undoubted biological efficacy and relatively low apparent toxicity make them attractive candidates for the management of osteoporosis. The bisphosphonate alendronate has many characteristics which suggest that it is suitable for use in osteoporosis. It is a potent inhibitor of osteoclast-mediated bone resorption with no adverse effect on the mineralization of bone. Earlier studies have shown it to be one of the most active bisphosphonates in Paget's disease and the hypercalcemia of malignancy. In common with other bisphosphonates tested thus far, alendronate appears to inhibit bone loss in a variety of experimental models of osteoporosis. Long-term studies are needed to determine its steady-state effects on bone mass in man. Most data indicate that alendronate is capable at least of decreasing the rate of bone loss, and might even induce increments in bone mass for many years. Since the experimental studies show that the increase in bone mass observed with alendronate is associated with an increase in bone strength, its use is likely to decrease the frequency of fractures. However, direct clinical evidence for this requires the outcome of well-designed long-term prospective studies.

Etidronic acid. A review of its pharmacological properties and therapeutic efficacy in resorptive bone disease

Etidronic acid is an orally and intravenously active bisphosphonate, which is believed to inhibit resorption of bone via a number of cellular mechanisms, including alteration of osteoclastic activity. In studies of patients with symptomatic Paget's disease, etidronic acid 5 to 20 mg/kg/day administered orally rapidly decreased the biochemical indices of bone turnover. Mineralisation defects in forming bone may be avoided by the use of an initial dosage of 5 mg/kg/day for up to 6 months; dosages above 10 mg/kg/day should be limited to 3 months' duration, and dosages greater than 20 mg/kg/day should be avoided. Although 3-day intravenous therapy with etidronic acid 7.5 mg/kg/day has shown superior efficacy to rehydration and forced diuresis in the management of hypercalcaemia of malignancy, the efficacy of the drug is lower than that of the newer bisphosphonates, pamidronic acid and clodronic acid. Clinical studies involving postmenopausal women with established osteoporosis have indicated that oral etidronic acid 400 mg/day for 14 days as part of a 90-day cycle, repeated for up to 3 years, increases the bone mineral density (BMD) of the lumbar vertebrae and appears to reduce the incidence of vertebral fracture. Published data suggest that etidronic acid shows similar efficacy to hormone replacement therapy (HRT) in these respects. The above dosage also appears to be effective in preventing corticosteroid-induced osteoporosis when administered as part of an intermittent, cyclical regimen. Etidronic acid in higher dosages (10 to 20 mg/kg/day orally) is effective in reducing the incidence of heterotopic ossification and its ensuing complications in both neurological and post-surgical patients. Etidronic acid is well tolerated by the majority of patients, with gastrointestinal complaints reported most commonly, but tends to delay the normal mineralisation of forming bone when administered continuously at higher dosages for prolonged periods. This is of little consequence where short term treatment is involved, but may be detrimental to those patients receiving longer courses of therapy. This effect may be minimised or avoided by using the lowest effective dosage for as short a time as possible (as in the above recommendations for Paget's disease), or by the use of intermittent cyclical therapy (as in the management of osteoporosis). Etidronic acid therefore retains a role in the management of resorptive bone disease, particularly in the treatment of Paget's disease, the prevention of heterotopic ossification, and as a second-line option in postmenopausal osteoporosis. However, the development of newer bisphosphonates requires that these compounds be continually compared and re-evaluated.

A comparison of the effects of oestrogen/progestogen, high-dose oral calcium, intermittent cyclic etidronate and an ADFR regime on calcium kinetics and bone mass in postmenopausal women with spinal osteoporosis

The effects of four different treatments for osteoporosis were compared in a prospective, randomized, 3-year study in 74 postmenopausal women with spinal crush fracture osteoporosis. Patients were randomly assigned to cyclic oestrogen/progestogen therapy (group 1, n = 20), a daily oral calcium dose of 2 g (group 2, n = 17), intermittent cyclic etidronate therapy (group 3, n = 19), or an ADFR treatment with triiodothyronine as activator and etidronate as depressor (group 4, n = 18). Spine and forearm bone mineral content was measured before entry and every 30 weeks. Combined calcium balance and 47Ca kinetic studies were performed before and after 1 and 3 years of treatment. Bone turnover, estimated by serum alkaline phosphatase and renal hydroxyproline excretion, decreased in all four groups during the first half of the treatment period but remained reduced during the second half in groups 1 and 3 only. Group 1 had a significantly positive calcium balance after 60 weeks of treatment. After 150 weeks, the positive effect on calcium balance was significant and greater in groups 1 and 3 than in the other groups. This was achieved by a greater reduction in resorption rate in group 1 at week 60 and in groups 1 and 3 at week 150 as compared with the other groups. Only group 1 had a significant increase in spinal bone mass while a decrease in bone mass at the distal forearm was observed in the etidronate-treated group. We conclude that treatment of postmenopausal osteoporosis with oestrogen/progestogen for 3 years results in net spinal bone gain and a positive effect on calcium balance slightly better than that of intermittent etidronate. These effects were inferior in the groups receiving a large calcium supplementation or the ADFR group where no change in calcium balance or bone mass was found.

Four-year study of intermittent cyclic etidronate treatment of postmenopausal osteoporosis: three years of blinded therapy followed by one year of open therapy

PURPOSE

To determine the effect of long-term intermittent cyclic etidronate treatment on spinal bone density and vertebral fracture rates.

PATIENTS AND METHODS

Postmenopausal osteoporotic women (n = 423) were randomized initially into a 2-year, double-blind, multicenter study; it was extended to a third year of blinded treatment followed by open-label treatment: 357 patients continued treatment in Year 3 (305 receiving blinded therapy and 52 receiving calcium supplementation) and 277 in Year 4. During Years 1 through 3, patients received double-blind treatment with phosphate (1.0 g) or placebo twice daily for 3 days, etidronate (400 mg) or placebo daily for 14 days, and calcium (500 mg) daily for the remainder of each 91-day treatment cycle. During Year 4, open-label intermittent cyclic etidronate therapy (without preceding phosphate) was administered to all patients. Spinal bone density and vertebral fracture rates were the main outcome measures.

RESULTS

During Year 3, etidronate therapy maintained the significant increases in spinal bone mineral density of the first 2 years. Over the 3-year period, proximal femur bone density increased in etidronate-treated patients. Etidronate therapy for 3 years significantly decreased the vertebral fracture rate in patients at higher risk for fracture (low spinal bone density and three or more vertebral fractures at study entry), as compared with nonetidronate treatment (228 versus 412 fractures per 1,000 patient-years, respectively; p < 0.05). After 1 year of open-label treatment, patients previously treated with etidronate maintained bone mass, and vertebral fracture rates in all groups were lower than in any other study period. There were no apparent serious adverse effects.

CONCLUSIONS

Three years of intermittent cyclic etidronate therapy produced significant increases in spinal and hip bone density, with a significant reduction in vertebral fracture rates in patients at higher fracture risk. Maintenance of bone mass and low fracture rate were observed when etidronate was continued for an additional year.

Clinical effects of bisphosphonates in involutional osteoporosis

The bisphosphonates are analogs of naturally occurring pyrophosphate. They appear to block bone resorption much more than mineralization. A series of compounds has been investigated. These have antiresorptive potencies ranging from 1 to 10,000. So far, structure-function relationships have eluded definition. These drugs increase the bone density in women with postmenopausal osteoporosis by about 5%-10% over 1 year. The bone density then appears to plateau, but most studies are of short duration. Improved bone density does not necessarily result in stronger bone, but no studies have had adequate power to assess fracture incidence. Bone formation rates decrease as measured histomorphometrically. This occurs while the bone density is improving, which implies an inhibition of bone resorption that is probably due to direct toxicity to the osteoclasts. Etidronate blocks mineralization as well as resorption and can cause osteomalacia, which is not seen with low-dose cyclical etidronate or with the second-generation compounds. The long-term effects of interfering with the remodeling cycle are still not known. Subtle side effects may be those on the bone itself. These might go undetected, since bone pain or fractures usually are attributable to the underlying disease.

Effects of one-year cyclical treatment with clodronate on postmenopausal bone loss

We studied 60 women with postmenopausal bone loss randomly allocated to the following treatments: Group 1 (20 patients), no treatment; Group 2 (20 patients), clodronate 400 mg daily by mouth for 30 consecutive days, followed by 60 days of no treatment; Group 3 (20 patients) oral calcitriol 2 mcg by mouth for 5 days and oral clodronate 400 mg daily for additional 25 days, followed by 60 days of no treatment. The therapeutic cycles were repeated four times in the 12-month study period. In the 36 treated patients of Groups 2 and 3 who completed the study period we observed a progressive and significant increase in lumbar bone density both at 6 and 12 months of therapy, without significant differences between the two treatment protocols (+3.88 +/- 0.65%, P < 0.001 and +3.21 +/- 0.89%, P < 0.005 in Groups 2 and 3, respectively, at the end of the study). In contrast, there was a progressive and significant decline of bone mineral density in untreated patients (-2.34 +/- 0.49%, P < 0.001). After 12 months serum calcium values in treated subjects were higher than in untreated patients (P < 0.05). Serum phosphate was raised only in Group 2, mean values being higher after 12 months than before treatment (P < 0.05); parathyroid hormone (PTH) declined in all treated patients, the fall being significant in Group 2 (P < 0.02). No important side effects were observed with treatment and no patient withdrew because of these. We conclude that cyclical low dose clodronate therapy induced a gain in lumbar spine bone mass in patients with postmenopausal osteoporosis.

Changes in bone histomorphometry after long-term treatment with intermittent, cyclic etidronate for postmenopausal osteoporosis

Intermittent, cyclic etidronate therapy (400 mg/day for 2 weeks followed by 13 weeks free from study drug administration) resulted in a significant increase in lumbar bone mineral content and a significant decrease in the rate of new vertebral fractures in patients with postmenopausal osteoporosis. To investigate the effect of the treatment on bone histomorphometry, transiliac crest bone biopsy samples were obtained in this study before treatment and after 60 and 150 weeks of treatment with either intermittent, cyclic etidronate (n = 33) or placebo (n = 33). After 60 weeks of etidronate therapy, significant decreases in activation frequency (from 0.55 to 0.09 year,-1 P < 0.01) and resorption depth (from 53.2 to 37.8 microns, P < 0.05) were observed, leading to a positive balance per remodeling cycle. In the placebo group, no significant changes were seen. The 150 week bone biopsy samples were suboptimal for analysis, probably as a result of a regional acceleratory phenomenon. Our results suggest that, as a result of reductions in both activation frequency and resorption depth, intermittent, cyclic etidronate therapy may protect the trabecular network against fortuitous perforations and thereby maintain the strength of the bony tissue.

New bisphosphonates in osteoporosis

Bisphosphonates are non-biodegradable compounds characterized by a phosphorus-carbon-phosphorus bond. By substituting the hydrogens on the carbon atom, a variety of bisphosphonates can be synthesized, each with distinct physical-chemical, biologic, therapeutic, and toxicologic characteristics. Bisphosphonates have in general a strong affinity to calcium phosphates, both in vitro and in vivo. They inhibit bone resorption through a cellular mechanism that is not yet completely understood. When given in large amounts, some bisphosphonates can inhibit normal and ectopic mineralization through a physical-chemical mechanism. The main difference among the various compounds appears to be their potency in inhibiting bone resorption, which can vary from 1 to 10,000. The potential efficacy of bisphosphonates in osteoporosis has been investigated extensively in animals. In the growing rat, they induce an increase in intestinal absorption and body retention of calcium. Various types of experimental osteoporosis, such as induced by immobilization, ovariectomy, administration of corticosteroids, or low calcium diet, can be prevented. Bisphosphonates are rapidly cleared from plasma, with 20%-60% deposited in bone and the remainder excreted in the urine. The half-life in bone is, however, very long. The toxicity of bisphosphonates is low, probably because of their rapid plasma and soft tissue clearance. It varies greatly from compound to compound. Bisphosphonates are used successfully in diseases with increased bone turnover, such as Paget's disease of bone, tumoral bone disease, and recently, osteoporosis. Most results in osteoporosis have been obtained with etidronate and pamidronate. Both of these compounds, as well as other bisphosphonates, such as tiludronate, alendronate, and clodronate, inhibit bone loss and sometimes even increase bone mass.(ABSTRACT TRUNCATED AT 250 WORDS)