Preliminary observations of a form of coherence therapy for osteoporosis

History of etidronate

Etidronate is a non-nitrogen-containing bisphosphonate. Because it binds with calcium and inhibits crystal formation and dissolution, it was considered by Procter & Gamble as an additive to toothpaste (to prevent build-up of tartar) and detergent (to bind calcium and increase sudsing in "hard" water). The first clinical use (1968) was for fibrodysplasia ossificans progressiva. The first approved clinical use (1977) was for treatment of Paget's disease of bone. Other approved indications are hypercalcemia of malignancy and heterotopic ossification, with a host of off-label uses (including fibrous dysplasia, periodontal disease, multiple myeloma, neuropathic arthropathy, pulmonary microlithiasis, diabetic retinopathy, bone metastases, melorheostosis, urinary stone disease, periodontal disease, etc.). Unique among bisphosphonates, etidronate (oral therapy) results in hyperphosphatemia, increased tubular reabsorption of phosphorus and increased levels of 1,25-dihydroxyvitamin D. The dose that reduces bone resorption is close to the dose that impairs mineralization; prolonged high-dose use can result in osteomalacia and bone fractures. Intermittent cyclic etidronate for osteoporosis resulted in favorable changes in bone density and histomorphometry (no mineralization defect) as well as a decrease in vertebral fracture rates in postmenopausal women with osteoporosis. Later studies showed similar effects in men with osteoporosis and patients with glucocorticoid-induced osteoporosis. Although its use for osteoporosis has given way to newer bisphosphonates and other agents, because of its unique properties, it remains the bisphosphonate of choice for treatment of heterotopic ossification.

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.

Biomedical applications of bisphosphonates

Since their discovery over 100 years ago, bisphosphonates have been used industrially as corrosion inhibitors and complexing agents. With the discovery of their pharmacological activity in the late 1960s, implicating their high affinity for hydroxyapatite, bisphosphonates have been employed in the treatment of bone diseases and as targeting agents for colloids and drugs. They have notably been investigated for the treatment of Paget's disease, osteoporosis, bone metastases, malignancy-associated hypercalcemia, and pediatric bone diseases. Currently, they are first-line medications for several of these diseases and are taken by millions of patients worldwide, mostly postmenopausal women. A major problem associated with their use is their low oral bioavailability. Several delivery systems have been proposed to improve their absorption and to direct them to sites other than bone tissues. Beyond their important pharmacological role, the medical applications of bisphosphonates are numerous. In addition, their metal-chelating properties have been exploited to coat and stabilize implants, nanoparticulates, and contrast agents. In this contribution, we review the pharmacological and clinical uses of bisphosphonates and highlight their novel applications in the pharmaceutical and biomedical fields.

Bisphosphonates for postmenopausal osteoporosis

Bisphosphonates are effective in reducing bone turnover, increasing BMD and reducing fracture risk in postmenopausal women with osteoporosis. The licensed bisphosphonates exhibit some differences in potency and speed of onset and offset of action. These differences mean that different agents may be more advantageous in different situations. Uncertainties still exist around the optimum duration of treatment and treatment holidays, how best to use bisphosphonates with anabolic treatments, and the benefits of treatment in patients who do not have a BMD T-score below -2.5.

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.).

Characterization andin vitro evaluation of biphasic calcium pyrophosphate–tricalciumphosphate radio frequency magnetron sputter coatings

The objective of this study was to characterize the physicochemical, dissolution, and osteogenic properties of radio frequency magnetron sputtered dicalcium pyrophosphate/tricalciumphosphate (Pyro/TCP) and hydroxylapatite (HA) coatings. Therefore Pyro/TCP and HA coatings were deposited on grit-blasted titanium discs. The results showed that the deposited coatings were amorphous and changed into a crystalline structure after IR heat-treatment of 550 degrees C for HA and 650 degrees C for Pyro/TCP. Heat-treated HA coatings appeared to be stable during immersion in simulated body fluid (SBF), that is no changes in the XRD pattern were observed. Also, no dissolution of the coating was observed by scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) revealed that the Ca/P ratio of the HA coatings remained constant during SBF immersion. On the other hand, the heat-treated Pyro/TCP coatings showed a surface reaction of calcium pyrophosphate into a beta-tricalcium phosphate phase during SBF immersion. This was confirmed by EDS analysis. Rat bone marrow-derived osteoblast-like cells cultured on the heat-treated substrates showed that cell proliferation and differentiation occurred on both types of bioceramic coatings. No significant differences for proliferation and early differentiation were observed between cells cultured on heat-treated Pyro/TCP and HA at individual time points. However, osteocalcin expression, a late marker for osteoblast-like cell differentiation, was significantly increased after 12 days of culture on HA-coatings. These results were confirmed by SEM observations and suggest increased osteogenic properties for HA-coatings over Pyro/TCP-coatings. Additional research is necessary to obtain conclusive evidence on the in vivo osteogenic capacity of Pyro/TCP coatings.

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.

Bone's mechanostat: a 2003 update

The still-evolving mechanostat hypothesis for bones inserts tissue-level realities into the former knowledge gap between bone's organ-level and cell-level realities. It concerns load-bearing bones in postnatal free-living bony vertebrates, physiologic bone loading, and how bones adapt their strength to the mechanical loads on them. Voluntary mechanical usage determines most of the postnatal strength of healthy bones in ways that minimize nontraumatic fractures and create a bone-strength safety factor. The mechanostat hypothesis predicts 32 things that occur, including the gross anatomical bone abnormalities in osteogenesis imperfecta; it distinguishes postnatal situations from baseline conditions at birth; it distinguishes bones that carry typical voluntary loads from bones that have other chief functions; and it distinguishes traumatic from nontraumatic fractures. It provides functional definitions of mechanical bone competence, bone quality, osteopenias, and osteoporoses. It includes permissive hormonal and other effects on bones, a marrow mediator mechanism, some limitations of clinical densitometry, a cause of bone "mass" plateaus during treatment, an "adaptational lag" in some children, and some vibration effects on bones. The mechanostat hypothesis may have analogs in nonosseous skeletal organs as well.

Injectable bisphosphonates in the treatment of postmenopausal osteoporosis

Osteoporosis is a "silent" disease and the patient has usually no clue of it until the occurrence of a fragility fracture. Prevention requires a continuous daily treatment that could be uncomfortable to the patient. Besides the recently introduced weekly oral schedules, injectable bisphosphonates have often been used as an off-label option to ameliorate compliance. In general, although with different efficiency, almost all injectable bisphosphonates can improve bone mineral density and suppress bone resorption markers. The effect of intravenous infusions of bisphosphonates are, to a large extent, similar to equivalent intramuscular administrations, but doses and dosing intervals represent the critical issues. Pain at the injection site and acute phase reactions are relatively common to intramuscular clodronate and intravenous infusions of nitrogen-containing bisphosphonates, respectively. Under certain circumstances, intermittent treatment with injectable bisphosphonates might represent a feasible alternative when compliance is at risk.

Bisphosphonate treatment of osteoporosis

Bisphosphonates represent the agents of choice for most patients with osteoporosis. They are the best studied of all agents for the prevention of bone loss and reduction in fractures. They increase BMD, primarily at the lumbar spine, but also at the proximal femur. In patients who have established osteoporosis, bisphosphonates reduce the risk of vertebral fractures, and are the only agents in prospective trials to reduce the risk of hip fractures and other nonvertebral fractures. Bisphosphonates reduce the risk of fracture quickly. The risk of radiographic vertebral deformities is reduced after 1 year of treatment with risedronate [68]. The risk of clinical vertebral fractures is reduced after 1 year of treatment with alendronate [69] and just 6 months' treatment with risedronate [157]. The antifracture effect of risedronate has been shown to continue through 5 years of treatment [158]. Alendronate and risedronate are approved by the FDA for prevention of bone loss in recently menopausal women, for treatment of postmenopausal osteoporosis, and for prevention (risedronate) and treatment (alendronate and risedronate) of glucocorticoid-induced osteoporosis. Alendronate is also approved for treatment of osteoporosis in men. Other bisphosphonates (etidronate for oral use, pamidronate and zoledronate for intravenous infusion) are also available and can be used off label for patients who cannot tolerate approved agents. Although bisphosphonates combined with estrogen or raloxifene produce greater gains in bone mass compared with single-agent treatment, the use of two antiresorptive agents in combination cannot be recommended because the benefit on fracture risk has not been demonstrated and because of increased cost and side effects.

The effect of sintered dicalcium pyrophosphate on osteoclast metabolism: an ultrastructural study

Sintered dicalcium pyrophosphate (SDCP), a synthetic compound, has proved to be both bioabsorbable and biocompatible in vivo. Recent work in our institute also has demonstrated that the ingestion of SDCP can increase bone mass in the ovariectomized rat. In this study, we used an in vitro cell culture model to investigate the ultrastructural changes and fate of osteoclasts induced by SDCP. Quantitative evaluation of osteoblasts and osteoclasts after administration of SDCP was performed. We studied immunohistochemical and ultrastructural features of osteoclasts undergoing apoptosis. The results showed that at 10(-4) M SDCP, the osteoblast cell count increased significantly, whereas the osteoclast population decreased significantly. Apoptosis of the osteoclast population was well demonstrated by immunohistochemical study. Ultrastructural study showed that the Golgi apparatus was degraded or dispersed in the cytoplasm. Later, osteoclasts revealed pyknotic nuclei showing condensation and margination of heterochromatins and DNA fragmentation, which are typical features of apoptosis. In addition, disruption of nuclear envelopes leading to leakage of nuclear contents into the cytoplasm was observed in the late stage of apoptosis. In conclusion, SDCP-induced apoptosis of osteoclasts was characterized by ultrastructural changes of the nucleus accompanied by degradation of cellular organelles.

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.

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.

Ultrastructural and cytochemical studies on cell death of osteoclasts induced by bisphosphonate treatment

The process of apoptosis and fate of osteoclasts are not well elucidated because dying osteoclasts are rarely seen in normal bone. Histological, cytochemical, and ultrastructural features of osteoclasts undergoing apoptosis were studied in the femur and tibia of rats treated with a third-generation bisphosphonate (disodium dihydrogen (cycloheptylamino)-methylene-1, 1-bisphosphonate). After the bisphosphonate administration, osteoclasts decreased significantly in number. Initially, they became devoid of ruffled borders and detached from the bone surface. In such osteoclasts, the Golgi apparatus was degraded, or dispersed in the cytoplasm. Later, osteoclasts revealed typical features of apoptosis, with pyknotic nuclei showing condensation and margination of heterochromatins and DNA fragmentation. They were often convoluted to give rise to apoptotic bodies. In addition, enlargement and fusion of nuclear envelopes and subsequent disruption leading to leakage of nuclear contents into the cytoplasm were observed in osteoclasts in the late stage of apoptosis. These osteoclasts as well as apoptotic bodies were surrounded by cytoplasmic processes of macrophages, which often contained degenerated cytoplasmic fragments of osteoclasts. Apoptotic osteoclasts migrating into or present in capillaries were also observed in some areas. In conclusion, bisphosphonate induces apoptosis of osteoclasts, which was characterized by ultrastructural changes of the nucleus typical of apoptosis accompanied by degradation of cell organelles. The majority of them are eliminated by macrophages, but there are some that escape into blood vessels.

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.

A four-year randomized controlled trial of hormone replacement and bisphosphonate, alone or in combination, in women with postmenopausal osteoporosis

PURPOSE

Hormone replacement therapy (HRT) with estrogen and treatment with bisphosphonates have been shown to increase bone mineral density (BMD) in postmenopausal women. This 4-year prospective randomized study was carried out to assess the effectiveness of the combined HRT plus etidronate on BMD in postmenopausal women with established osteoporosis.

PATIENTS AND METHODS

Seventy-two postmenopausal women (mean age 64.9+/-0.5 years) attending metabolic bone disease outpatient clinics with established osteoporosis were randomly allocated into one of four treatment groups and monitored for 4 years. All patients enrolled in this study including the control group (n=18) received 1.0 g elemental calcium and 400 units vitamin D per day. The HRT group (n=18) received cyclical estrogen and progesterone; the etidronate group (n=17) received intermittent cyclical etidronate; and the combined therapy group (n=19) received both HRT and etidronate. BMD was measured in the lumbar spine and the hip before treatment and at 2 and 4 years after treatment. Changes in height were recorded, and the occurrence of new vertebral fractures were documented in comparison with the baseline radiographic evaluation. In 40 patients (10 patients per group), analysis of bone histomorphometry was carried out after 4 years of treatment.

RESULTS

In patients who received the combined therapy, BMD increased in the lumbar spine by 10.4% (P <0.001) and in the hip by 7.0% (P <0.001) at 4 years. For patients treated with ICE, these increases were 7.3% (P <0.001) and 0.9% (P <0.05), and with HRT, the increases were 7.0% (P <0.001) and 4.8% (P <0.01) in the vertebrae and femora, respectively. The group treated with calcium and vitamin D lost 2.5% (P <0.05) and 4.4% (P <0.01) of BMD in the vertebrae and femora, respectively, after 4 years. Patients who received combined therapy had significantly higher BMD in both the vertebrae and in the femora (P <0.05) in comparison with patients who were treated with HRT or etidronate alone after 4 years. In comparison with patients in the control group, there was a trend toward a lower rate of new vertebral fractures in the treatment groups. Height loss was significantly less in all three active treatment groups (HRT [P <0.001], etidronate [P <0.02], and combined therapy group [P <0.0001]), in comparison with the control group. The combined therapy group did not have a significant height loss, in comparison with the HRT (P <0.02) and the etidronate (P <0.001) groups. None of the patients had histomorphometric evidence of osteomalacia.

CONCLUSION

This 4-year randomized study showed an additive effect of etidronate and HRT on hip and spine BMD in postmenopausal women with established osteoporosis.

Sustained response to intravenous alendronate in postmenopausal osteoporosis

We studied the effects of alendronate (amino-hydroxybutylidene bisphosphonate) on biochemical indices of bone turnover and on lumbar spinal bone mineral density in 15 postmenopausal women with vertebral osteoporosis. Alendronate 7.5 mg daily was administered intravenously as a slow infusion for four consecutive days. Treatment was associated with a significant decrease in serum calcium (p < 0.01), fasting urinary calcium excretion (p < 0.01) and hydroxyproline excretion within several days followed a later decrease in serum alkaline phosphatase activity that showed a significant reduction at two months after treatment (p < 0.05). Serum calcium reverted to pretreatment values by the second week after infusion, but the decrease in alkaline phosphatase, urinary calcium, and hydroxyproline excretion persisted to six months after infusion. There was a 3% mean increase in lumbar bone mineral density at six months (p < 0.01). A transient lymphopenia or leucopenia was noted in eight patients and a short-lived fever in six. No other side effects were observed. This study demonstrates that shortterm exposure to high intravenous doses of alendronate induces suppression of bone resorption in osteoporosis that persists for at least 6 months after infusion. We conclude that a short exposure to high intravenous doses induces sustained effects on bone turnover in much the same manner as that observed in Paget's disease of bone.

The role of bisphosphonates in the prevention and treatment of osteoporosis

The first-generation biphosphonate etidronate is used only experimentally in osteoporosis prevention. Its effects in treating osteoporosis have been studied only in subjects who already have vertebral crush fractures. No reduction in the incidence of fractures in this population as a whole has been established. The suggestion of a more pronounced beneficial effect seen in severely osteoporotic patients treated with bisphosphonates for two years that seems to emerge from a posteriori analysis must be confirmed. The long-term safety of this therapy is currently under study. Subsequent generations of bisphosphonates are still experimental, whether for prevention or treatment.

Effect of tamoxifen citrate on canine immobilization (disuse) osteoporosis

The effect of tamoxifen citrate on bone mass in immobilization osteoporosis was studied in 11 growing dogs. Immobilization osteoporosis was induced by fiberglass cast immobilization of the right hindlimb for 28 days, while the left hindlimb served as a nonimmobilized control. Six dogs received tamoxifen citrate (1.5 mg/kg per os) once daily for 28 days; five dogs received no treatment. All dogs were euthanatized on day 28 and bone samples were collected. Bone mineral content of the distal tibial metaphysis of casted and uncasted limbs was measured by single photon absorptiometry. Immobilization resulted in a significant reduction in bone mass in the casted limb of untreated and tamoxifen-treated dogs. However, tamoxifen-treated dogs had less severe immobilization osteoporosis than untreated dogs. The calculated bone mass sparing effect of tamoxifen was 24.4%. Because of the complexity of pathologic bone remodeling, use of a single therapeutic agent may not be the optimal means of preventing bone loss associated with immobilization.

The influence of dichloromethylene bisphosphonate on the healing of a long bone fracture, composition of bone mineral and histology of bone in the rat

The effects of dichloromethylene bisphosphonate (clodronate) on the composition of bone mineral, morphology and histology of a long bone with an artificial femoral fracture were studied in a 22 week experiment. Two hundred twenty-four female rats were allocated to dose groups of 0, 3, 10, and 30 mg/kg clodronate daily subcutaneously. Bone calcium, phosphorus and magnesium concentrations remained stable and fluoride concentration rose with time. There were no statistical differences between different groups. Clodronate did not alter the histology of the callus nor delayed the healing of the fracture. It caused mild to moderate prominence of the metaphyseal area in the fractured bone in a dose- and time-dependent manner. Serum osteocalcin levels were lowered in the treated animals dose-dependently. Other serological as well as haematological values were within normal range. Clodronate seems in this experimental arrangement to be a safe agent to administer in different pathological conditions of bone even when they are complicated by fractures of long bones.

Clinical experience with etidronate in osteoporosis

Clinical experience with cyclical etidronate for the treatment of osteoporosis was reviewed in 69 consecutive patients. Six patients stopped treatment either due to adverse effects (5) or the decision to take hormone replacement therapy (HRT) (1). Bone mineral density (BMD) measurements using dual energy X-ray absorptiometry (DXA) were obtained in 63 patients (33 with spinal osteoporotic fractures and 30 with osteopenia) before and 1 year after treatment. BMD increased by an average of 4.50% (p < 0.001) in the lumbar spine (range +14% to -12%) and 5.5% (p < 0.01) at Ward's triangle (range +31% to -13%) while there was no significant change at the femoral neck (range +11% to -12%) and greater trochanter (range +12% to -15%). Significant rises in BMD were found at the lumbar spine and Ward's triangle in both osteoporotic and osteopenic groups. Of patients analysed after 1 year, 83% had an increased bone mass at the lumbar spine and 55% at the femoral neck. We conclude that there is a wide variation in the bone mass response to cyclical etidronate therapy, and in a minority of patients bone mass does not increase. For the majority of osteoporotic patients, however, we confirm the efficacy and tolerability of cyclical etidronate for the preservation of bone mass over 1 year in a clinical setting.

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.

Short-term oral phosphate and bone remodeling in beagles

Attempts to increase bone volume in osteoporotic patients are still in the experimental stage. The coherence therapy, proposed by Frost, suggests that the activated bone units can remodel bone matrix in tandem. The cells (i.e., osteoclast and osteoblast which compose the remodeling units) are manipulated through specific medications timed to each of their duration of actions. The current study was to examine the effect of withdrawal of oral phosphate on bone in ovariectomized dogs. The present report demonstrates the capability of short-term oral phosphate to activate bone remodeling in the ovariectomized animal model. Results from biochemical and histomorphometric analyses confirm that remodeling units are activated following the release of parathyroid hormone. This transient scenario inflicts a shift of mineral density distribution in cancellous bone matrix of the iliac crest. Nevertheless, the bone remodeling units appear to be synchronized with each other and thus their resorptive and formative phases should be amenable to further pharmacological manipulation.

A new bisphosphonate, BM 21.0955, prevents bone loss associated with cessation of ovarian function in experimental dogs

We previously found that bone loss occurs as soon as 1 month after ovariohysterectomy (OHX) in beagle dogs. Indirect evidence pointed to an early dramatic increase in bone resorption. To verify this hypothesis and evaluate the effects of a newly developed bisphosphonate, BM 21.0955 (Boehringer Mannheim), 36 beagle dogs were subjected to OHX and 12 dogs were sham operated (Sham). OHX dogs were divided into six groups (n = 6 each) and received subcutaneous injections of vehicle or BM 21.0955 at various doses (0.1, 0.3, 1, 10, and 100 micrograms/kg/day) for 1 month. Sham dogs were given vehicle (n = 6) or BM 21.0955 (1 microgram/kg/day, n = 6). Iliac crest biopsies and blood drawings were done at baseline and at month 1. OHX dogs given vehicle exhibited a decrease in cancellous bone volume associated with an increase in erosion depth and a decrease in serum levels of 1,25-dihydroxyvitamin D. BM 21.0955 prevented the bone loss at a dose > or = 1 microgram/kg and the increase in erosion depth and the decrease in serum levels of 1,25-(OH)2D at a dose > or = 0.3 microgram/kg. No osteomalacia was observed at any dose of BM 21.0955. Bone turnover was reduced only when BM 21.0955 was administered at doses of 10 or 100 micrograms/kg. There were no changes in body weight or serum levels of calcium, phosphorus, creatinine, parathyroid hormone, or osteocalcin in all groups. The increase in erosion depth in OHX dogs given vehicle proves that the early rapid bone loss after cessation of ovarian function is related to an increase in osteoclastic activity. The antiosteoclastic activity of BM 21.0955 at a dose > or = 1 microgram/kg prevents this increase and preserves bone volume. The absence of any signs of osteomalacia at any dose confers a relatively wide therapeutic margin to BM 21.0955. BM 21.0955 at a dose > or = 10 micrograms/kg also acts as an inhibitor of bone turnover. This is not observed at a dose of 1 microgram/kg, at least after 1 month of administration.

Skeletal effects of withdrawal of estrogen and diphosphonate treatment in ovariectomized rats

The study was designed to determine the skeletal effects of withdrawal of estrogen and diphosphonate treatment in the estrogen-deplete state. Groups of ovariectomized (OVX) rats were treated with vehicle alone, estrogen, or the diphosphonates etidronate or risedronate for a 180-day period. A group of sham-operated control rats was treated for 180 days with vehicle alone. All treatments were then terminated, followed by sequential sacrifice of rats at 0, 35, 90, 180, and 360 days after withdrawal of treatment. The proximal tibia from each animal was processed undecalcified for quantitative bone histomorphometry. At the end of the treatment period, vehicle-treated OVX rats were characterized by cancellous osteopenia and increased bone turnover relative to vehicle-treated control rats. Treatment of OVX rats with estrogen or diphosphonates depressed bone turnover and protected against cancellous osteopenia. During the withdrawal period, OVX rats previously treated with estrogen exhibited rapid bone loss associated with increased bone turnover. The bone protective effect of the hormone in OVX rats was nearly completely lost by 90 days of withdrawal. In contrast, OVX rats maintained low levels of bone turnover and normal cancellous bone mass at 180 days of withdrawal from diphosphonate treatment. The results suggest that estrogen-deplete women who are withdrawn from estrogen replacement are at high risk for subsequent bone loss. They further suggest that widely spaced periods of intermittent diphosphonate treatment may be sufficient to prevent the development of osteopenia in postmenopausal and oophorectomized women.

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)

[Preventive drug therapy of postmenopausal osteoporosis]

Osteoporosis, one of the most important disorders associated with aging, needs active prevention. Estrogen therapy prevents the early phase of bone loss and decreases the incidence of subsequent osteoporosis related fractures. All estrogens are probably not equally effective against post menopausal bone loss. In USA conjugated equine estrogens are the most used. In Europe estrogen therapy is usually applied with 17 beta estradiol with different ways of administration. If estrogen therapy cannot be used, there are limited datas about the use of bisphosphonates or calcitonins in the prevention of post menopausal bone loss, but not still any data about the subsequent incidence of fractures. In all cases, calcium supplementation is effective.

Rationale for the use of clodronate in osteoporosis

Bisphosphonates are widely used in disorders associated with increased resorption of bone, particularly in Paget's disease of bone and in the hypercalcemia of malignancy. Because of their undoubted efficacy and relatively low toxicity, bisphosphonates are attractive candidates for the management of osteoporosis. Clodronate, one of the many bisphosphonates being tested in osteoporosis, may be given intravenously or by mouth. In contrast to etidronate, even high doses of clodronate do not impair the mineralization of bone, making it suitable for long-term use in osteoporosis. As do all the bisphosphonates tested thus far, clodronate appears to delay the rate of bone loss in osteoporosis. Long-term studies are relatively few, so that its steady-state effects on bone mass are not yet known. Most data suggest clodronate is capable at least of delaying the rate of bone loss, but several pilot studies with this agent suggest that increments of bone mass might be sustainable for several years. Clodronate is likely to decrease the frequency of osteoporotic fractures, but there is no evidence for this at present. Well-controlled, long-term prospective studies are needed.

Bone hypertrophy and trabecular generation in Paget's disease and in fluoride-treated osteoporosis

The replacement of lost trabeculae characteristic of postmenopausal osteoporosis is problematic, since a biological pathway has not been established for trabecular regeneration de novo in the healthy, intact, mature skeleton. Possible pathways for trabecular replacement may occur under pathological conditions, in particular those associated with bone hypertrophy. The topography of trabecular hypertrophy was compared in two groups of subjects with disease- or treatment-induced osteosclerosis following a period of atrophy. In Paget's disease and fluoride-treated osteoporosis a thickening of rarefied trabeculae in both was associated in Paget's disease only with an increase in the trabecular number and the transformation of a discontinuous arrangement into a more continuous network. The sequence seems to be a progression of intratrabecular resorption normally attendant upon a period of trabecular thickening. The failure of fluoride-treated bone in this respect, due to the unusual stability of the fluorotic skeleton, may provide insight to more effective anabolic regimens.

The role of changes in mechanical usage set points in the pathogenesis of osteoporosis

Mechanical usage (MU) effects on modeling drifts and BMU-based remodeling affect bone mass in defined ways. Decreased MU stops additions of bone by modeling and increases removal of bone next to marrow by remodeling. The latter effect thins cortices and reduces trabecular number, thickness, and connectivity. Return to normal MU makes remodeling begin conserving existing bone and leaves modeling still off. Hypervigorous MU can make modeling increase bone mass during growth and makes remodeling keep conserving it in children and adults. These effects can be said to begin when typical bone strains rise through two threshold ranges, one for remodeling and a higher one for modeling. Raising the thresholds while normal MU continues should give bone a spurious disuse message, whereupon disuse effects would begin. The bone anatomic and tissue dynamic patterns in acute and chronic disuse resemble those seen in developing and acquired postmenopausal osteoporosis and in other forms of osteoporosis, too. If some hormones, drugs, and other agents increase those thresholds, this could explain such similarities.

Production of new trabecular bone in osteopenic ovariectomized rats by prostaglandin E2

Serum chemistry and bone morphometry of the proximal tibial metaphysis were performed in 3-month-old double fluorescent-labeled, female Sprague-Dawley rats subjected to bilateral ovariectomy or sham surgery for 4 months prior to treatment with 0, 0.3, 1, 3, or 6 mg of prostaglandin E2 (PGE2)/kg/day subcutaneously for 30 days. The 4-month postovariectomized rats possessed an osteopenic proximal tibial metaphysis with 7% trabecular area compared with controls (19%). PGE2 treatment elevated osteocalcin levels and augmented proximal tibial metaphyseal bone area in ovariectomized and sham-operated rats. Osteopenic, ovariectomized rats treated with 6 mg PGE2/kg/day for 30 days restored bone area to levels of age-matched sham-operated rats. Morphometric analyses showed increased woven and lamellar bone area, fluorescent-labeled perimeter (osteoblastic recruitment), mineral apposition rate (osteoblastic activity), bone formation rate (BFR/BV), and longitudinal bone growth. These dramatic bone changes were all significantly increased at the dose-response manner. This study showed that in vivo PGE2 is a powerful activator of bone remodeling, it increases both bone resorption and bone formation, and produces an anabolic effect by shifting bone balance to the positive direction. Furthermore, PGE2-induced augmentation of metaphyseal bone area in ovariectomized rats was at least two times greater than in sham-operated rats.

Toward a cure for osteoporosis: reversal of excessive bone fragility

While estrogen replacement therapy and calcium supplementation appear to be effective at preventing postmenopausal osteoporosis, therapy for established osteoporosis is far less effective. The reduction of bone fragility should be a goal of a treatment for established osteoporosis. To this end, increases in cortical bone mass by subperiosteal new bone formation may produce the greatest mechanical advantage. Anti-resorptive drugs, such as etidronate, have shown potential for reducing the incidence of osteoporotic fracture in the short term, but their ability to produce a long-term benefit may be limited. An alternative approach might be to develop drug therapies that substantially increase cortical bone strength, namely by stimulating periosteal bone formation. Although sodium fluoride has proved to be problematic, there are several other potential osteoporosis therapies. They include treatment with anabolic hormones (e.g. growth hormone and anabolic steroids) and targeted delivery of growth factors. Also, anti-resorptive and formation-stimulating drugs might be combined in a new form of ADFR (coherence) therapy where the new acronym means: Activate-Depress-Formation stimulation-Repeat.

Bone densitometric and histomorphometric responses to sequential human parathyroid hormone (1-38) and salmon calcitonin in osteoporotic patients

Cyclical treatments of osteoporosis utilizing a skeletal Activator of bone remodelling, and sequential therapy with a Depressor to selectively block the resulting phase of osteoclastic resorption have been dubbed 'ADFR' therapy; there is usually a treatment Free interval while the activated bone multicellular units complete the remodelling cycle before the protocol is Repeated. In this report an ADFR protocol was developed in which all patients received synthetic hPTH (1-38) for the first 14 days of a 100 day cycle. Half the patients received no other therapy (Group 1), but were followed closely with repeated vertebral bone mineral measurements over two full cycles. The remaining patients (Group 2) were randomly allocated to receive salmon calcitonin, at an average dose of 79 units per day for a 56 day depressor period immediately following each phase of activation. Detailed bone histomorphometry was performed on iliac biopsies obtained before treatment and at the end of the second cycle (Day 200). In Group 1, the serum alkaline phosphatase (Alk. P'ase) increased by 23 +/- 12% (P less than 0.01) and by 18 +/- 16% (P less than 0.03) of the baseline values following PTH treatment during the first and second cycles, respectively. The overall changes in serum Alk. P'ase across time were significantly less (P less than 0.04) in Group 2; however this parameter also increased by 15 +/- 15% during the first cycle and 8 +/- 6% during the second cycle. Vertebral BMC increased by 13% in Group I (P less than 0.01), but forearm BMC decreased by 11% (P less than 0.05) over the two cycles of therapy. There were no significant changes in bone mineral measurements in Group 2, but the differences between the two groups were not significant. Eighteen paired biopsies were available for histomorphometric analysis. There were no significant changes in static parameters measuring total bone tissue, osteoclastic function or osteoid formation after two cycles of treatment. Individual bone formation rates (surface referent) were not significantly different between the two groups; the pooled data for all biopsies showed a small but insignificant increase from 0.030 +/- 0.018 to 0.035 +/- 0.028 mm3/mm2/day. However there was a significant increase in the activation frequency (the probability of a remodelling event occurring on queiscent cancellous surface) from 13 +/- 7 to 27 +/- 26/day x 10(-4) (P less than 0.05) when calculated for the pooled data from both groups.(ABSTRACT TRUNCATED AT 400 WORDS)

A new direction for osteoporosis research: a review and proposal

This article suggests why drugs that only reduce the activity of existing osteoclasts or enhance the activity of existing osteoblasts probably cannot cure the osteopenias associated with most osteoporoses. Instead they should add only limited amounts of bone, which should begin to disappear after treatment stops. That behavior depends on these facts. Different threshold ranges of mechanical bone strains control gains and losses of bone mass. One threshold controls gains by modeling drifts, and a lower one controls losses by remodeling BMUs. A drug that does not change those thresholds should limit gains (or losses) of bone during indefinitely continued treatment. Success in curing those osteopenias should require learning how to change the thresholds.

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

Thirty-seven patients were randomized to receive intermittent cyclic etidronate (400 mg/day oral for 2 weeks, followed by 13 weeks off treatment) or an ADFR treatment (100 micrograms/day oral triiodothyronine for 7 days, followed by 400 mg/day etidronate for 2 weeks and 12 weeks off treatment). Supplemental calcium (120 mg/day) and vitamin D3 (400 IU/day) were given throughout the study period to all patients. Biochemical analyses, iliac-crest bone biopsies, and lumbar bone mineral content (BMC) measurements were performed before and during 60 weeks of treatment. Sixteen patients in the intermittent cyclic etidronate group and 15 in the ADFR group completed 60 weeks of treatment. Serum alkaline phosphatase decreased from 185 (43) (mean, (SD] to 144 (35) (p less than 0.001) and from 221 (69) to 156 (43) (p less than 0.002) during intermittent cyclic etidronate treatment and ADFR treatment, respectively, without any significant changes in renal hydroxyproline excretion. Final resorption depth, trabecular bone activation frequency, and bone formation rate decreased significantly from 51.5 (48.4/60.0) microns (median (25%/75% quartiles] to 44.0 (39.6/46.2) microns (p less than 0.04), from 0.30 (0.17/0.62) year-1 to 0.10 (0.02/0.19) year-1 (p less than 0.03) and from 0.035 (0.020/0.081) microns3/microns2/day to 0.015 (0.002/0.025) microns3/microns2/day, p less than 0.03 respectively, during intermittent cyclic etidronate treatment, but were unchanged during ADFR treatment. No significant changes in trabecular bone volume, bone balance per remodeling cycle, or BMC were noted in either treatment group; no evidence of osteomalacia was found. Intermittent cyclic etidronate treatment may be effective in preventing bone loss and in decreasing the risk of trabecular plate perforation, and thereby maintaining the integrity of bone architecture, in postmenopausal osteoporosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Intermittent cyclical etidronate treatment of postmenopausal osteoporosis

BACKGROUND

To determine the effects of etidronate (a bisphosphonate that inhibits osteoclast-mediated bone resorption) in the treatment of postmenopausal osteoporosis, we conducted a prospective, two-year, double-blind, placebo-controlled, multicenter study in 429 women who had one to four vertebral compression fractures plus radiographic evidence of osteopenia.

METHODS

The patients were randomly assigned to treatment with phosphate (1.0 g) or placebo twice daily on days 1 through 3, etidronate (400 mg) or placebo daily on days 4 through 17, and supplemental calcium (500 mg) daily on days 18 through 91 (group 1, placebo and placebo; group 2, phosphate and placebo; group 3, placebo and etidronate; and group 4, phosphate and etidronate). The treatment cycles were repeated eight times. The bone density of the spine was measured by dual-photon absorptiometry, and the rates of new vertebral fractures were determined from sequential radiographs.

RESULTS

After two years, the patients receiving etidronate (groups 3 and 4) had significant increases in their mean (+/- SE) spinal bone density (4.2 +/- 0.8 percent and 5.2 +/- 0.7 percent, respectively; P less than 0.017). The rate of new vertebral fractures was reduced by half in the etidronate-treated patients (groups 3 and 4 combined) as compared with the patients who did not receive etidronate (groups 1 and 2 combined) (29.5 vs. 62.9 fractures per 1000 patient-years; P = 0.043); the effect of treatment was most striking in the subgroup of patients with the lowest spinal bone mineral density at base line, in whom fracture rates were reduced by two thirds (42.3 vs. 132.7 fractures per 1000 patient-years; P = 0.004). The addition of phosphate provided no apparent benefit. There were no significant adverse effects of treatment.

CONCLUSIONS

Intermittent cyclical therapy with etidronate for two years significantly increases spinal bone mass and reduces the incidence of new vertebral fractures in women with postmenopausal osteoporosis.

Effect of intermittent cyclical etidronate therapy on bone mass and fracture rate in women with postmenopausal osteoporosis

Progressive bone loss in osteoporosis results from bone resorption in excess of bone formation. We conducted a double-blind study in 66 women with postmenopausal osteoporosis of therapy with etidronate, a diphosphonate compound that reduces bone resorption by inhibiting osteoclastic activity. The patients were randomly assigned in equal numbers to receive oral etidronate (400 mg per day) or placebo for 2 weeks, followed by a 13-week period in which no drugs were given. This sequence was repeated 10 times, for a total of 150 weeks. Daily oral supplementation with calcium and vitamin D was given throughout the study to both groups. Vertebral bone mineral content was measured by dual-photon absorptiometry; spinal radiographs were assessed to identify new vertebral fractures. Vertebral bone mineral content increased significantly (P less than 0.01) after 150 weeks of etidronate therapy (5.3 percent; 95 percent confidence interval, 2.0 to 8.6; n = 20) but decreased with placebo (-2.7 percent; 95 percent confidence interval, -7.3 to 1.9; n = 20). The difference between groups was 8.0 percentage points (P less than 0.01; 95 percent confidence interval, 2.4 to 13.6). The rates of fracture were significantly different for the period from week 60 to week 150 between the etidronate and placebo groups (6 vs. 54 fractures per 100 patient-years; P = 0.023). No adverse clinical, biochemical, or bone histomorphometric effects of treatment were observed. We conclude that at the end of nearly three years, etidronate therapy for postmenopausal osteoporosis results in significant increases in vertebral bone mineral content and, after approximately one year of treatment, a significant decrease in the rate of new vertebral fractures.

Biochemical responses to sequential human parathyroid hormone (1-38) and calcitonin in osteoporotic patients

Parathyroid hormone (PTH) has been proposed as a skeletal activator for cyclical protocols of treatment for osteoporosis; among several potential drugs that might serve to depress the subsequent phase of osteoclastic bone resorption, calcitonin is the most selective. Twenty patients aged 50-78 years were enrolled in a study of their biochemical responses during a 14-day activation cycle with synthetic hPTH 1-38, given as a subcutaneous injection of 400 IU/day; half the patients were randomly allocated to receive a subsequent 56-day depressor cycle with calcitonin in a dose of 100 U/day, while the remainder received no further treatment. All patients received an initial 24-h intravenous infusion of hPTH 1-38 (0.5 U/kg/h) to evaluate the PTH-dependent renal synthesis of 1,25(OH)2D. Serum calcium increased from 2.20 +/- 0.07 mmol/l to 2.56 +/- 0.16 (P less than 0.005) during PTH infusion, but was not significantly different from baseline during intermittent treatment. Baseline concentrations of serum 1,25(OH)2D were 22.8 +/- 8.2 pg/ml, increased to 52.2 +/- 25.1 (P less than 0.005) during infusion and remained significantly higher than baseline after 14 days intermittent therapy (33.1 +/- 19.4, P less than 0.05). Gastrointestinal absorption of 45Ca, as represented by alpha (peak fractional absorption/h), increased from 0.397 +/- 0.173 to 0.552 +/- 0.210 (P less than 0.01) during hPTH 1-38 therapy and was moderately correlated with the increment in serum 1,25(OH)2D levels (r = 0.5, P less than 0.03). Daily calcium excretion was significantly increased above baseline during hPTH 1-38 therapy, but there were no correlations between changes in urinary calcium, alpha or serum 1,25(OH)2D levels. Baseline fasting urinary excretion of OH-proline increased during hPTH 1-38 treatment from 30.5 +/- 13.9 mol/mmol creatinine to 43.4 +/- 17.5 immediately after hPTH 1-38 infusion (P less than 0.025), and mean excretion was persistently higher than baseline during intermittent treatment; the increased urine calcium and OH-proline excretion are consistent with PTH-induced activation of bone resorption. Serum alkaline phosphatase and osteocalcin levels increased significantly during a 90-day period of observation after the hPTH 1-38 cycle, which is consistent with increased osteoblast activity in association with coupled bone formation.(ABSTRACT TRUNCATED AT 400 WORDS)

Errors in bone remodeling: toward a unified theory of metabolic bone disease

Recent evidence suggests that skeletal adaptation is organized by a functional unit that includes cells of diverse origin working in coordination. Genetic and metabolic factors control and regulate the processes of modeling and remodeling, only rarely acting on the isolated individual functions of specific cell lines. Errors in the genetic or metabolic regulation of the functional unit affect the entire process of skeletal adaptation rather than specific elements of it. Viewed in this way, some metabolic bone diseases can be understood as relatively simple errors in factors that control the coordinated activities of the entire functional unit. This paper reviews the modeling and remodeling processes and demonstrates how abnormal morphological characteristics of bone tissue can be viewed as products of specific errors in the adaptive process.