Clinical experience with pamidronate in the treatment of Paget's disease of bone

Drug treatment strategies for Paget's disease: relieving pain and preventing progression

INTRODUCTION

Paget's disease of bone (PDB) is a focal bone disorder caused by a marked dysregulation of osteoblasts and osteoclasts in basic multicellular units, leading to abnormal and disorganized deposition of collagen fibers (the so-called "woven bone"). Therefore, pagetic bones are increased in size, and at increased risk for bone pain, deformities, fractures, osteoarthritis, and, more rarely, neoplastic degeneration.

AREAS COVERED

In this review we revise the available information concerning the pharmacological treatment of PDB.

EXPERT OPINION

PDB progresses slowly within the affected skeletal sites and, if untreated, often leads to bone overgrowth, with bone pain, deformity and a likely increased risk of complications. Thus, the primary goal of treatment is the restoration of a normal bone turnover, in order to relieve bone pain or other symptoms and possibly prevent the complications. PDB long remained a poorly treatable disorder until the discovery of antiresorptive agents such as calcitonin first and bisphosphonates (BPs) later. With the recent development of potent intravenous BPs like zoledronate, allowing a better control of disease activity over the long term with a single infusion, has contributed to a marked improvement of the clinical management of this invalidating disorder.

Bisphosphonates in the management of Paget's disease

The first clinical use of bisphosphonates was in Paget's disease of bone (PDB) when disodium etidronate was found to be effective at suppressing metabolic activity of the disease. Subsequently, PDB became a testing ground for many bisphosphonates using changes in alkaline phosphatase (ALP) as the primary outcome measure in clinical trials. Bisphosphonates are now considered to be the treatment of choice for PDB since they are highly effective at suppressing the elevations in bone turnover that are characteristic of the disease. Short term studies have shown that treatment with alendronate and risedronate can promote formation of lamellar bone in affected sites and improve x-ray appearances in some patients. Bisphosphonates have also been shown to improve bone pain in PDB and within the bisphosphonates, zoledronic acid (ZA) is most likely to give a favourable pain response. Many patients with PDB do not have pain however, even when there is increased metabolic activity and more research is needed to find out why this is the case. The effects of bisphosphonates on complications of PDB such as deformity, pathological fractures and deafness have not been adequately studied since most clinical trials have been short term and have not collected information on these important outcomes. The PRISM and PRISM-EZ studies investigated the long-term effects of bisphosphonates in patients with established PDB using a treat-to-target approach and showed that intensive bisphosphonate therapy aimed at normalising ALP was no more effective than symptom directed treatment with bisphosphonates at preventing complications of PDB. The Zoledronate in the Prevention of Paget's Disease (ZiPP) trial, which is currently in progress, seeks to determine whether early intervention with this potent bisphosphonate might be effective in preventing disease progression. Should the ZiPP study yield positive results, genetic testing coupled to prophylactic bisphosphonate therapy might represent a new indication for these highly effective inhibitors of bone resorption in future years.

Adult Paget's disease of bone: a review

Adult PD of bone is the second commonest metabolic bone condition after osteoporosis. The condition is characterized by increased bone cell activity, with bone-resorbing osteoclasts often larger and containing more nuclei than normal, and osteoblasts producing increased amounts of disorganized bone. This leads to expanded bone of poor quality possessing both sclerotic and lytic areas. PD of bone has a strong genetic element, with a family history being noted in 10-20% of cases. A number of genetic defects have been found to be associated with the condition. The most common disease-associated variants identified affect the SQSTM1 gene, providing insights into disease aetiology, with the clinical value of knowledge of SQSTM1 mutation status currently under active investigation. The diagnosis may be suggested by an isolated raised total ALP without other identifiable causes. This can be confirmed on plain X-rays and the extent determined by isotope bone scan. The mainstays of treatment are the bisphosphonates, especially i.v. zoledronate, which results in long-term suppression of bone turnover. ALP is the usual means of monitoring the condition, although more specific bone turnover markers can be helpful, especially in coincident liver disease. Patients should be followed up to monitor for biochemical relapse or development of complications, which may require medical or surgical intervention.

Bisphosphonates for Paget's disease of bone in adults

BACKGROUND

Bisphosphonates are considered to be the treatment of choice for people with Paget's disease of bone. However, the effects of bisphosphonates on patient-centred outcomes have not been extensively studied. There are insufficient data to determine whether reducing and maintaining biochemical markers of bone turnover to within the normal range improves quality of life and reduces the risk of complications.

OBJECTIVES

To assess the benefits and harms of bisphosphonates for adult patients with Paget's disease of bone.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, ISI Web of Knowledge and trials registers up to March 2017. We searched regulatory agency published information for rare adverse events.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of bisphosphonates as treatment for Paget's disease in adults.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened search results, extracted data and assessed studies for risk of bias. We used standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We included 20 trials (25 reports, 3168 participants). Of these, 10 trials (801 participants) compared bisphosphonates (etidronate, tiludronate, ibandronate, pamidronate, olpadronate, alendronate, risedronate, zoledronate) versus placebo, seven compared two bisphosphonates (992 participants), one trial compared a bisphosphonates with a bisphosphonate plus calcitonin (44 participants), and two studies, the largest trial (1331 participants) and its interventional extension study (502 participants), compared symptomatic treatment and intensive treatment where the goal was to normalise alkaline phosphatase.Most studies were assessed at low or unclear risk of bias. Six of 10 studies comparing bisphosphonates versus placebo were assessed at high risk of bias, mainly around incomplete outcome data and selective outcome reporting.Participant populations were reasonably homogeneous in terms of age (mean age 66 to 74 years) and sex (51% to 74% male). Most studies included participants who had elevated alkaline phosphatase levels whether or not bone pain was present. Mean follow-up was six months.Bisphosphonates versus placeboBisphosphonates tripled the proportion (31% versus 9%) of participants whose bone pain disappeared (RR 3.42, 95% confidence interval (CI) 1.31 to 8.90; 2 studies, 205 participants; NNT 5, 95% CI 1 to 31; moderate-quality evidence). This result is clinically important. Data were consistent when pain change was measured as any reduction (RR 1.97, 95% CI 1.29 to 3.01; 7 studies, 481 participants).There was uncertainty about differences in incident fractures: 1.4% fractures occurred in the bisphosphonates group and none in the placebo group (RR 0.89, 95% CI 0.18 to 4.31; 4 studies, 356 participants; very low-quality evidence).None of the studies reported data on orthopaedic surgery, quality of life or hearing thresholds.Results regarding adverse effects and treatment discontinuation were uncertain. There was a 64% risk of mild gastrointestinal adverse events in intervention group participants and 48% in the control group (RR 1.32, 95% CI 0.91 to 1.92; 6 studies, 376 participants; low-quality evidence). The likelihood of study participants discontinuing due to adverse effects was slightly higher in intervention group participants (4.4%) than the control group (4.1%) (RR 1.01, 95% CI 0.41 to 2.52; 6 studies, 517 participants; low-quality evidence). Zoledronate was associated with an increased risk of transient fever or fatigue (RR 2.57, 95% CI 1.21 to 5.44; 1 study, 176 participants; moderate-quality evidence).Bisphosphonates versus active comparatorMore participants reported pain relief with zoledronate than pamidronate (RR 1.30, 95% CI 1.10 to 1.53; 1 study, 89 participants; NNT 5, 95% CI 3 to 11) or risedronate (RR 1.36, 95% CI 1.06 to 1.74; 1 study, 347 participants; NNT 7, 95% CI 4 to 24; very low quality evidence). This result is clinically important.There was insufficient evidence to confirm or exclude differences in adverse effects of bisphosphonates (RR 1.05, 95% CI 0.95 to 1.76; 2 studies, 437 participants; low-quality evidence) and treatment discontinuation (2 studies, 437 participants) (RR 2.04, 95% CI 0.43 to 9.59; 2 studies, 437 participants; very low-quality evidence).Intensive versus symptomatic treatmentThere was no consistent evidence of difference to response in bone pain, bodily pain or quality of life in participants who received intensive versus symptomatic treatment.Inconclusive results were observed regarding fractures and orthopaedic procedures for intensive versus symptomatic treatment (intensive treatment for fracture: RR 1.84, 95% CI 0.76 to 4.44; absolute risk 8.1% versus 5.2%; orthopaedic procedures: RR 1.58, 95% CI 0.80 to 3.11; absolute risk 5.6% versus 3.0%; 1 study, 502 participants; low-quality evidence).There was insufficient evidence to confirm or exclude an important difference in adverse effects between intensive and symptomatic treatment (RR 1.05, 95% CI 0.79 to 1.41; low-quality evidence).There was insufficient evidence to confirm or exclude an important difference of risk of rare adverse events (including osteonecrosis of the jaw) from the regulatory agencies databases.

AUTHORS' CONCLUSIONS

We found moderate-quality evidence that bisphosphonates improved pain in people with Paget's disease of bone when compared with placebo. We are uncertain about the results of head-to-head studies investigating bisphosphonates. We found insufficient evidence of benefit in terms of pain or quality of life from intensive treatment. Information about adverse effects was limited, but serious side effects were rare, and rate of withdrawals due to side effects was low.

Diagnosis and management of Paget's disease of bone

OBJECTIVE

To conduct a literature review on the diagnosis and management of Paget's disease of bone.

MATERIALS AND METHODS

This scientific statement was generated by a request from the Brazilian Medical Association (AMB) to the Brazilian Society of Endocrinology and Metabolism (SBEM) as part of its Clinical Practice Guidelines program. Articles were identified by searching in PubMed and Cochrane databases as well as abstracts presented at the Endocrine Society, Brazilian Society for Endocrinology Annual Meetings and the American Society for Bone and Mineral Research Annual Meeting during the last 5 years. Grading quality of evidence and strength of recommendation were adapted from the first report of the Oxford Centre for Evidence-based Medicine. All grades of recommendation, including "D", are based on scientific evidence. The differences between A, B, C and D, are due exclusively to the methods employed in generating evidence.

CONCLUSION

We present a scientific statement on Paget's disease of bone providing the level of evidence and the degree of recommendation regarding causes, clinical presentation as well as surgical and medical treatment.

Intravenous pamidronate for refractory rheumatoid arthritis

BACKGROUND

Patients with rheumatoid arthritis may be resistant to conventional treatment with disease-modifying antirheumatic drugs (DMARDs). On the other hand, biologic therapy is costly and may be inconvenient for many patients. Pamidronate is a potent bisphosphonate with the capacity of modifying the biological activity of the immune system cells. It may thus be used as an anti-inflammatory agent in patients with inflammatory joint diseases.

MATERIALS AND METHODS

To assess the effectiveness of pamidronate in the management of rheumatoid arthritis, we selected 38 patients with rheumatoid arthritis to enroll in a pilot study to receive pamidronate and conventional treatment with prednisolone and DMARDs in combination. These patients received 60 mg of pamidronate for 3 consecutive months and were followed for 6 months since the first infusion.

RESULTS

The mean visual analogue score (VAS) and disease activity score (DAS28) fell steadily until one month after the third infusion. However, no improvements were observed during the 3 months after the last infusion of the drug. All patients, except one, reported decreased pain in response to 3 consecutive pulses of pamidronate and most had improvements in the assessed laboratory and clinical indices. The drug was tolerated well in our patients.

CONCLUSION

Pamidronate infusions had beneficial effects on various clinical and laboratory parameters of patients, but alleviation of symptoms were temporary and did not last for more than 6 months. This treatment option can be a choice for difficult cases of rheumatoid arthritis with severe pain and osteoporosis.

Current options for the treatment of Paget's disease of the bone

Paget’s disease of bone (PDB) is a chronic bone remodelling disorder characterized by increased osteoclast-mediated bone resorption, with subsequent compensatory increases in new bone formation, resulting in a disorganized mosaic of woven and lamellar bone at affected skeletal sites. This disease is most often asymptomatic but can be associated with bone pain or deformity, fractures, secondary arthritis, neurological complications, deafness, contributing to substantial morbidity and reduced quality of life. Neoplastic degeneration of pagetic bone is a relatively rare event, occurring with an incidence of less than 1%, but has a grave prognosis. Specific therapy for PDB is aimed at decreasing the abnormal bone turnover and bisphosphonates are currently considered the treatment of choice. These treatments are associated with a reduction in plasma alkaline phosphatase (ALP) activity and an improvement in radiological and scintigraphic appearance and with a reduction in bone pain and bone deformity, Recently, the availability of newer, more potent nitrogen-containing bisphosphonates has improved treatment outcomes, allowing a more effective and convenient management of this debilitating disorder.

Comparison of different intravenous bisphosphonate regimens for Paget's disease of bone

This randomized study compared different intravenous bisphosphonates in PDB. Zoledronate was superior with respect to pamidronate in achieving biochemical remission, with therapeutic response maintained in most patients at 15 mo. Single neridronate and zoledronate infusion showed a similar efficacy in up to 90% of patients nonresponders to pamidronate.

INTRODUCTION

Intravenous bisphosphonates represent a common therapy for Paget's disease of bone (PDB). However, there have been few head to head randomized trials comparing intravenous bisphosphonates.

MATERIALS AND METHODS

We performed a 15-mo, randomized study comparing different intravenous bisphosphonates in 90 subjects with active PDB. At baseline, patients were randomly assigned to receive pamidronate (30 mg, i.v., for 2 consecutive days every 3 mo; n = 60) or zoledronate (4 mg, i.v.; n = 30). After 6 mo, nonresponders to pamidronate were crossed over to zoledronate or neridronate (100 mg, i.v., for 2 consecutive days). The primary efficacy endpoint was therapeutic response at 6 mo, defined as normalization of alkaline phosphatase (ALP) or a reduction of at least 75% in total ALP excess.

RESULTS

At 6 mo, 97% of patients receiving zoledronate had a therapeutic response compared with 45% of patients receiving pamidronate. Normalization of ALP was achieved in 93% of patients in the zoledronate group and in 35% of patients in the pamidronate group. ALP normalization was maintained in 79% and 65% of zoledronate-treated patients after 12 and 15 mo, respectively; loss of therapeutic response was observed in 2 of 30 (6%) at 12 and 15 mo. At 6 mo, 27 patients showing therapeutic response to pamidronate continued the treatment, whereas nonresponders were crossed-over to neridronate (n = 15) or zoledronate (n = 18). Among these subjects, 14 of 15 (93%) in the neridronate group and 17 of 18 (94%) in the zoledronate group achieved a therapeutic response. Similar normalization rates were observed between neridronate- (80%) and zoledronate- (83%) treated subjects. Normalization and therapeutic response were maintained at 9 mo from treatment (corresponding to 15 mo from the baseline visit) in either neridronate or zoledronate groups.

CONCLUSIONS

Single neridronate and zoledronate infusion showed a similar efficacy in achieving biochemical remission in up to 90% of patients nonresponders to pamidronate. Therapeutic response to zoledronate seems to be maintained in most patients at 15 mo.

Intravenously administered pamidronate in the treatment of Paget's disease of bone

OBJECTIVE

To evaluate the effect of intravenously administered pamidronate in patients with Paget's disease of bone.

METHODS

We conducted a prospective nonrandomized study and reviewed the related literature. Eighty patients (52 women and 28 men, ranging in age from 53 to 93 years; mean age, 76) were treated with pamidronate intravenously in a total dose of 180 mg during a 6- or 3-week period. All patients had bone scintigraphy and x-ray findings characteristic of Paget's disease of bone. Serum alkaline phosphatase levels were increased in all patients, and findings on fractionation were consistent with a bone origin. Indications for therapy included extensive disease, pagetic deformities, neurologic complications, pagetic pain, and critical areas of involvement. Blood chemistry profile and complete blood cell counts were determined at baseline and after the last dose of pamidronate. Serum calcium levels were determined after the first and second infusions of pamidronate. Patients underwent clinical and biochemical follow-up assessments, with serum alkaline phosphatase measurements, at 2- to 4-month intervals. Many patients who did not have a remission (defined as normalization of serum alkaline phosphatase level) after the first cycle of therapy or who had a relapse with serum alkaline phosphatase levels increased above the normal range after remission were treated with one or more cycles of intravenously administered pamidronate.

RESULTS

The mean serum alkaline phosphatase level was 1,051 U/L before therapy and 386 U/L after treatment, a decrease of 63% (P<0.0001). In 50 patients, the serum alkaline phosphatase level declined to normal. Such normalization was noted in 43 of 50 patients (86%) whose baseline alkaline phosphatase was less than 3 times the upper limit of normal (ULN), in 5 of 13 patients (38%) whose baseline alkaline phosphatase was 3 to 6 times the ULN, and in only 2 of 17 patients (12%) whose baseline alkaline phosphatase exceeded 6 times the ULN. Of 30 patients who did not have a remission, 22 received a second course of therapy, 2 of whom had normalization of the serum alkaline phosphatase level. Pamidronate was well tolerated; only nine patients reported a "flu-like" syndrome after the first infusion. Serum calcium levels decreased in many patients (to as low as 8 mg/dL), but no patients were symptomatic.

CONCLUSION

With intravenous administration of pamidronate in a dose of 180 mg in patients with Paget's disease of bone, remissions are likely in those whose baseline serum alkaline phosphatase level is <3 times the ULN and unlikely when baseline alkaline phosphatase levels are higher-especially more than 6 times the ULN.

Paget's disease of bone

Paget's disease of bone is a localized disorder of bone remodeling. Increased numbers of larger than normal osteoclasts initiate the process at affected skeletal sites, and the increase in bone resorption is followed by an increase in new bone formation, altering bone architecture. The signs and symptoms of Paget's disease are varied, depending in part on the location of the involved sites and the degree of increased bone turnover. Recent progress in Paget's disease research includes new data regarding the etiology of this disorder and the ongoing development of more effective therapies. Although the cause of Paget's disease remains unproven, the creation of pagetic osteoclasts seems ever more likely to result from both genetic and environmental factors. Many studies indicate that in patients with Paget's disease, both osteoclasts and their precursors harbor evidence of a paramyxovirus infection, although not all studies confirm this finding. Very recent genetic investigations have identified one candidate gene on chromosome 18q, although genetic heterogeneity is almost certainly present. Advances in treatment have resulted from the availability of several potent bisphosphonate compounds (e.g., pamidronate, alendronate, and risedronate) that, unlike earlier treatments, produce normal or near normal bone turnover indices in a majority of patients. New bone formation after such treatment has a more normal, lamellar pattern, and mineralization abnormalities are rare to absent with the newer compounds. The availability of such agents has prompted a more aggressive management philosophy in which both symptomatic disease and also asymptomatic disease at sites with a risk of progression and future complications are viewed as clear indications for pharmacologic intervention.

Pamidronate. A review of its use in the management of osteolytic bone metastases, tumour-induced hypercalcaemia and Paget's disease of bone

Pamidronate (APD) is a potent inhibitor of bone resorption that is useful in the management of patients with osteolytic bone metastases from breast cancer or multiple myeloma, tumour-induced hypercalcaemia or Paget's disease of bone. After intravenous administration, the drug is extensively taken up in bone, where it binds with hydroxyapatite crystals in the bone matrix. Matrix-bound pamidronate inhibits osteoclast activity by a variety of mechanisms, the most important of which appears to be prevention of the attachment of osteoclast precursor cells to bone. In patients with osteolytic bone metastases associated with either breast cancer or multiple myeloma, administration of pamidronate together with systemic antitumour therapy reduces and delays skeletal events, including pathological fracture, hypercalcaemia and the requirement for radiation treatment or surgery to bone. Pamidronate generally improves pain control. Quality-of-life and performance status scores in pamidronate recipients were generally as good as, or better than, those in patients who did not receive the drug. Overall survival does not appear to be affected by pamidronate therapy. Tumour-induced hypercalcaemia also responds well to pamidronate therapy: 70 to 100% of patients achieve normocalcaemia, generally 3 to 5 days after treatment. Response durations vary, but are commonly 3 weeks or longer, In comparative studies, pamidronate produced higher rates of normocalcaemia and longer normocalcaemic durations than other available osteoclast inhibitors, including intravenous etidronate, clodronate and plicamycin (mithramycin). In most patients with Paget's disease of bone, intravenous pamidronate reduces bone pain and produces biochemical response. Serum alkaline phosphatase levels generally fall 50 to 70% from baseline 3 to 4 months after pamidronate treatment. Biochemical response may be prolonged. Pamidronate is well tolerated by most patients. Transient febrile reactions, sometimes accompanied by myalgias and lymphopenia, occur commonly after the first infusion of pamidronate. Other reported adverse events include transient neutropenia, mild thrombophlebitis, asymptomatic hypocalcaemia and, rarely, ocular complications (uveitis and scleritis). Pamidronate should be considered for routine use together with systemic hormonal or cytotoxic therapy in patients with breast cancer or multiple myeloma and osteolytic metastases. At present, pamidronate is the drug of choice for first-line use in the management of patients with tumour-induced hypercalcaemia. It is an effective treatment for Paget's disease and is the treatment of choice where oral bisphosphonates are not an option.

Clinical, biochemical, hematologic, and radiographic responses in Paget's disease following intravenous pamidronate disodium: a 2-year study

An intravenous dosage schedule using pamidronate disodium, based on biochemical severity, was used to treat 71 patients with Paget's disease who had no previous bisphosphonate treatment. Disease severity was stratified by fasting hydroxyproline excretion (HypE): Group (Gp) I (mild disease; HypE < 5.0 mumol/LGF) received a total dose of 120 mg; Gp II (moderate; HypE 5.00-9.99) received 180 mg; and Gp III (severe; HypE > or = 10) received 240 mg. Within each group patients were randomly allocated to receive daily 30 mg or 60 mg infusions. Observations for 2 years included pain scores, indices of bone turnover, and radiology of lytic lesions. There was no difference in biochemical responses, or in the percentage of patients with early fever, between the 30 mg and 60 mg daily subgroups; for convenience, 60 mg infusions are recommended. Neutrophils and total white cell counts were both significantly below baseline 4 days after the first infusion; lymphocytes were significantly reduced by day 2; and all three measures had returned to within the reference range by day 6. Remission was assessed at 6 months, when both plasma alkaline phosphatase (ALP) and HypE had reached stable nadirs. Increasing severity was associated with increasing resistance to suppression of HypE at 6 months to within the reference range: Gp I, 87%; Gp II, 44%; and Gp III, 0% (p < 0.0001 by chi-square test). Biochemical relapse at 2 years (defined as ALP 50% above the 6 month level) was also dependent on initial disease severity (Gp I, 6%; GpII, 39%; Gp III, 62%; p < 0.0005 by chi-square test). There was no association between time to relapse and either initial dose or log dose. Radiologic lytic lesions (in 22 patients) were all in remission at 3 months; however, relapse rates at 2 years appeared to be severity-dependent: Gp I, 13%; Gp II, 43%; and Gp III, 57% (n.s. by chi-square test). Remission rates based on a fall to < 50% of pretreatment of either HypE or ALP were more in accord with lytic lesion remission rates than were rates based on HypE falling to within the reference range. Pamidronate produced a significant reduction from baseline in Pagetic bone, Pagetic joint, and unrelated musculoskeletal pain in the first 6 months (p < 0.0001). From 0 months to 2 years the maintenance of improvement in bone pain (p < 0.005) and joint pain (p < 0.05) was significantly better than in unrelated pain. Pamidronate is a safe, welltolerated, and effective treatment for Paget's disease. In spite of larger dosage in severe disease, increasing severity was associated with resistance to normalization of biochemistry and a higher incidence of biochemical and radiological relapse at 2 years. Our current dosage recommendation would be for two 60 mg infusions for mild disease (Gp I); and four 60 mg infusions for moderate disease (Gp II). Severe disease (Gp III) remains a challenge; regardless of dosage, the majority of patients will be in relapse 2 years after a single course of treatment.

Bisphosphonates and the treatment of bone disease in the elderly

Recognition of the way in which naturally occurring pyrophosphate affects bone metabolism has stimulated the development of a whole series of related compounds, the bisphosphonates. Although the precise mechanism of action of these compounds remains incompletely understood, they have been proven profoundly effective in clinical practice and already constitute a major advance in the therapy of conditions characterised by excessive bone resorption. Serious adverse effects are rare; however, mineralisation problems are a concern, particularly with etidronate. The reduction in bone turnover during prolonged treatment for osteoporosis is also a concern but as yet of uncertain clinical importance. The wide variation in potency of different bisphosphonates in inhibiting the resorption, mineralisation and turnover of bone will increasingly determine which agents are used in various clinical situations. Bisphosphonates are the treatment of choice in Paget's disease and hypercalcaemia of malignancy. They also appear to have potential to alter the course of metastatic bony disease, although the magnitude and clinical importance of any such effect remains unclear. Bisphosphonates show promise in the prevention and treatment of osteoporosis and increase bone mass in postmenopausal and steroid-induced osteoporosis. The effects of these drugs in other situations are less clear and the effects on fracture rates are not yet fully characterised. Optimal regimens have yet to be established but the long half-lives of these agents makes intermittent treatment a rational and convenient approach.

Therapeutic strategy in Paget's disease of bone

Paget's disease of bone is a localized progressive disease, characterized by increased bone remodeling, bone hypertrophy, and abnormal bone structure, leading to pain and deformity. Disease complications involve the bones, joints, and central nervous system. Short-term treatment objectives are to alleviate or suppress bone pain; the long-term aim is for the prevention of complications caused by the slow disease progression in affected bones. The lifetime risk of complications depends on life expectancy, location, and activity index of Paget's disease. The use of potent and safe new bisphosphonates (tiludronate, pamidronate, alendronate, risedronate, and others) represents a major advance for the management of the condition: these compounds permit normalization of the biochemical indices of remodeling, and clinical doses have lasting effects without disruption to bone mineralization. Bone histomorphometry has shown that bisphosphonates can restore normal bone structure and an optimal therapeutic strategy should be defined. Symptomatic patients (or asymptomatic patients at risk) should be treated, as well as any patient requiring orthopedic surgery. The optimum strategy for preventing complications is to treat as early as possible and to halt disease progression by normalizing the biochemical markers that reflect the increased bone remodeling. There is no consensus on the threshold values for retreatment. Few studies have evaluated the long-term effects of the inhibitors of osteoclastic resorption on the risk of complications. A recent 12 year, long-term follow-up of 41 cases of Paget's disease has shown that antipagetic therapy that did not normalize biochemical markers in 71% of patients did not prevent new complications in 62% of patients. These results suggest that an optimal regimen of treatment and retreatment should target normalization of biochemical markers of bone remodeling; the new bisphosphonates make this quite feasible in most patients.

Effects of intravenous pamidronate therapy on Paget's disease of bone

Pamidronate is a second generation bisphosphonate that has been used in Europe for the treatment of Paget's disease of bone for several years. It relieves pain and reduces bone turnover in Paget's disease. To assess the effects of pamidronate on Paget's disease of bone, the authors treated 28 patients, aged 45 to 87, with longstanding Paget's disease for a period of 4-18 months. Parameters measured included pain and serum alkaline phosphatase, urinary hydroxyproline, and ionized calcium concentrations. Patients were organized into two groups. Patients in the first group had initial alkaline phosphatase concentrations below 215 U/L, which decreased to normal after one dose of pamidronate. Patients in this group also experienced symptomatic improvement. Patients in the second group had initial alkaline phosphatase values greater than 240 U/L, which did not normalize after 2-11 pamidronate infusions. More patients in this latter group did not report symptomatic improvement. Patients in the second group also had a higher incidence of hypocalcemia. It is concluded that there is a clear relation between initial alkaline phosphatase level in Paget's disease and response to treatment with pamidronate. The authors' current protocol for treating patients with pamidronate is based on this relation. Because pamidronate proved most effective when used in mild Paget's disease, therapy probably should be instituted early in the course of disease.

Pharmacological management of back pain syndromes

The symptom of back pain may be the result of many different pathologies. As such, patients with back pain require careful assessment to determine whether the cause is from the spine or other systems. For acute mechanical back pain, treatment is often symptomatic. Symptomatic treatment may include analgesics, anti-inflammatories and/or muscle relaxants. Patients may also need hypnotics in the short term to help them sleep at night. However, drug therapy should be reduced and stopped as soon as possible. Furthermore, too much bedrest may be counterproductive. Paracetamol (acetaminophen) is the standard treatment for transient back pain. More severe pain may require the addition of an opioid, such as codeine or dextropropoxyphene. Morphine and pethidine (meperidine) may be necessary in patients with back pain due to neoplastic disease or osteoporotic fracture. However, the opioid analgesics are associated with dependence, tolerance and adverse effects. Nonsteroidal anti-inflammatory drugs (NSAIDs) have analgesic efficacy comparable with paracetamol. Individual patients respond differently to different NSAIDs, and several agents may have to be tried. Long term therapy with NSAIDs is necessary in diseases with an inflammatory component such as ankylosing spondylitis. Calcitonin reduces bone resorption and bone blood flow, and has been suggested to have central analgesic effects. As such, it has been used successfully in patients with Paget's disease, osteolytic bone disease and osteoporosis. Bisphosphonates also inhibit osteoclastic bone resorption and may be useful in Paget's disease, osteolytic metastases and osteoporotic fractures. Other drugs which may be useful in relieving back pain associated with specific circumstances include the tricyclic antidepressants, anxiolytics, antiepileptic agents, corticosteroids, colchicine and chymopapain.

Mineralisation defects with pamidronate therapy for Paget's disease

Bone biopsy samples were taken from 20 patients with Paget's disease before and after intravenous pamidronate therapy. In 10 patients given 180 or 360 mg during 6 or 9 weeks, bone turnover decreased as measured biochemically and histologically, but osteomalacia developed in 1 patient and mineralisation defects in 3. 10 other patients received 45 mg every 3 months for 1 year. Bone turnover decreased biochemically but not histologically, and osteoid thickness increased, suggesting impaired mineralisation. Despite overall efficacy, pamidronate has a narrow therapeutic range between resorption inhibition and mineralisation defects. Short courses given to achieve biochemical remission should be administered with caution.

Determinants of remission of Paget's disease of bone

Bisphosphonates are a safe and effective treatment for Paget's disease of bone, but little information is available about the factors influencing the duration of remission so obtained. We assessed 60 patients with Paget's disease treated with disodium pamidronate (APD). The mean duration of remission was 9.5 months (range 3-25). The major influences were the initial pretreatment alkaline phosphatase (ALP; r = -4.6, p < 0.0001), minimum posttreatment ALP (r = -0.51, p < 0.0001), and the rate of response of bone turnover to the first dose of APD (r = 0.61, p < 0.0001). Multiple linear regression showed that the initial response to treatment was the most significant influence. Also, despite a minimum ALP within the normal range, the duration of remission varied considerably (4-25 months). This may be due to the difficulties in applying a population-based normal range to individuals.

Drugs used in the treatment of metabolic bone disease. Clinical pharmacology and therapeutic use

Osteoporosis is the most important metabolic bone disease and places an increasing burden on the healthcare system. The condition can be prevented by the early introduction of hormone replacement therapy. The role of bisphosphonates in achieving the same result is being actively explored. The attraction of preventing bone loss is that it preserves the micro-architecture of bone, and therefore its mechanical integrity. The great problem of treating the established condition is that substantial bone loss is accompanied by architectural disintegration. Replacing lost bone may not necessarily restore mechanical integrity and protect against fractures. The management of Paget's disease has been quite revolutionised by the introduction of the bisphosphonates. The condition is a result of a primary increase in osteoclastic bone resorption which can be corrected by bisphosphonates, with considerable symptomatic improvement. The increasing potency and safety margin of the newer agents has meant that the threshold for treatment has fallen. There is now potential for long term control of bone turnover with the hope of preventing late complications. Hypercalcaemia of malignancy is usually the result of both increased bone destruction and decreased urinary calcium excretion. These two components of hypercalcaemia demand different approaches to management. The general availability of an ever-expanding range of increasingly potent bisphosphonates has resulted in a dramatic improvement in the treatment of increased bone resorption associated with malignancy. Many types of tumour, either directly or indirectly, compromise the ability of the kidney to eliminate a calcium load derived from increased bone destruction. Calcitonin is the only agent which is currently available to counter this process.

Treatment of Paget's disease of bone with single dose intravenous pamidronate

OBJECTIVES

To assess the efficacy of a single intravenous infusion of pamidronate in Paget's disease of bone.

METHODS

Fourteen patients with active Paget's disease (raised serum alkaline phosphatase, bone pain or neurological involvement) were treated with a single intravenous infusion of 105 mg pamidronate. Patients were assessed for biochemical and clinical improvement for up to two years following treatment. A further infusion was given following symptomatic relapse (pain at a known site of pagetic involvement).

RESULTS

Serum alkaline phosphatase fell following treatment, with a nadir 5.9 months after treatment. Bone pain was improved in nine of 12 patients after six months. Retreatment of four patients resulted in a similar response.

CONCLUSION

Single dose intravenous pamidronate (105 mg) is a convenient and effective treatment for Paget's disease.

Newer agents for the treatment of malignant hypercalcemia

The treatment of malignant hypercalcemia has involved fluids, diuretics, and specific calcium-lowering therapy with mithramycin and calcitonin. However, newer agents have recently been approved for the treatment of hypercalcemia due to malignancy. This review will discuss three such agents, gallium, etidronate, and pamidronate. This review will concentrate on the clinical pharmacologic characteristics and the clinical trials of these newer agents. Their use in the clinical practice will be suggested based on review of the published literature.

Intravenous pamidronate in the treatment of osteoporosis associated with corticosteroid dependent lung disease: an open pilot study

BACKGROUND

Bisphosphonates have been shown to be effective agents in the treatment of postmenopausal osteoporosis. Because corticosteroid associated osteoporosis is often associated with increased bone turnover, the effect of intermittent intravenous infusions of pamidronate on this condition has been investigated.

METHODS

Seventeen patients (five male) with chronic corticosteroid dependent lung disease (15 asthma, two sarcoidosis) were treated with infusions of 30 mg pamidronate once every three months for one year. These patients had been taking an average of 14 (range 7.5-40) mg prednisolone a day for an average of 14 (range 3-30) years. Bone density measurements, by dual energy x ray absorptiometry, and radiography of the dorsolumbar spine were carried out before and one year after treatment. Bone formation was assessed by measurement of serum alkaline phosphatase and bone resorption by measurement of the fasting urinary hydroxyproline: creatinine ratio at the same time as densitometry and radiography were performed.

RESULTS

Pretreatment density of L2-4 and the neck of the femur was significantly lower in these patients compared with a cohort of 100 age and sex matched controls (L2-4 (mean (SEM)): 0.906 (0.050) g/cm2 v 1.142 (0.016) g/cm2; neck of femur: 0.793 (0.030) g/cm2 v 0.936 (0.013)) g/cm2. After treatment there was a significant fall in serum alkaline phosphatase activity from (mean (SEM)) 220 (16) U/1 to 174 (9) U/1 (normal 80-280 U/1) and in the fasting urinary hydroxyproline:creatinine ratio from (mean (SEM) 0.040 (0.006) to 0.024 (0.003) (normal < 0.033). A significant rise was noted in L2-4 density to 0.927 (0.047) g/cm2; mean rise of 3.4%). No change was noted in density of the neck of the femur.

CONCLUSIONS

Intermittent infusions of intravenous pamidronate would seem to be effective in both reducing turnover of bone and increasing bone density in corticosteroid induced osteoporosis associated with chronic lung disease. Longer term controlled studies are indicated.