Calcitriol. A review of its use in the treatment of postmenopausal osteoporosis and its potential in corticosteroid-induced osteoporosis

Recent advance of small-molecule drugs for clinical treatment of osteoporosis: A review

Osteoporosis is a metabolic bone disorder typified by a reduction in bone mass and structural degradation of bone tissue, leading to heightened fragility and vulnerability to fractures. The incidence of osteoporosis increases with age, making it a significant public health challenge. The pathogenesis of osteoporosis involves an imbalance between osteoblast-mediated bone formation and resorption. The current treatment options for osteoporosis include bisphosphonates, hormone replacement therapy (HRT), selective estrogen receptor modulators (SERMs), and denosumab. The recent advances in small-molecule drugs for the clinical treatment of osteoporosis offer promising options for improving bone health and reducing fracture risk. This review aims to provide an overview of the clinical applications and synthetic routes of representative small-molecule drugs for the treatment of osteoporosis. A comprehensive understanding of the synthetic methods of drug molecules for osteoporosis may inspire the development of new, more effective, and practical synthetic techniques for treating this condition.

The Role of Vitamin D in Small Animal Bone Metabolism

Dogs and cats have differences in vitamin D metabolism compared to other mammalian species, as they are unable to perform vitamin D cutaneous synthesis through sun exposure. Therefore, they are dependent on the dietary intake of this nutrient. The classic functions of vitamin D are to stimulate intestinal calcium and phosphate absorption, renal calcium and phosphate reabsorption and regulate bone mineral metabolism. Thus, it is an important nutrient for calcium and phosphorus homeostasis. This review highlights the evidence of the direct and indirect actions of vitamin D on bone mineral metabolism, the consequences of nutritional imbalances of this nutrient in small animals, as well as differences in vitamin D metabolism between different size dogs.

The efficacy of calcitriol therapy in the management of bone loss and fractures: a qualitative review

Osteoporosis, a skeletal disorder characterized by a reduction in bone strength, increases fracture risk. Primary osteoporosis is usually a result of reduced bone mineral density as a consequence of natural aging. Secondary osteoporosis is usually a result of a disease, such as cystic fibrosis, or medical treatment, such as corticosteroids or cancer treatment.

INTRODUCTION

Currently, ten million Americans are osteoporotic and an additional 34 million have the precursor condition, osteopenia. Osteoporosis leads to 1.5 million fractures and 500,000 hospitalizations annually. Osteoporosis-related fractures increase mortality and reduce quality of life. Calcitriol, the active form of vitamin D, regulates intestinal calcium absorption, among other actions. During the past four decades, many clinical trials investigating the effect of calcitriol on bone loss have been performed.

METHODS

We conducted a systematic qualitative review of clinical trials that assessed calcitriol for the treatment of osteoporosis and bone loss. In these clinical trials, calcitriol was used as a monotherapy and in combination with other therapeutic bone agents.

RESULTS AND CONCLUSION

Studies using calcitriol monotherapy, although not conclusive, found that calcitriol slowed the rate of bone loss in a variety of populations. Calcitriol in combination with other therapeutic bone agents was shown to have additional bone-preserving effects when compared to the use of therapeutic bone agents alone. A common side-effect of calcitriol therapy was hypercalcemia and hypercalciuria, but the degree of hypercalcemia was mild. Recent research found that intermittent dosing can reduce hypercalcemia rates. Calcitriol, alone or in combination with other agents, should be considered for the therapy of osteoporosis.

Alendronate in combination with calcium and vitamin D prevents bone loss after orthotopic liver transplantation: a prospective single-center study

Bone loss is a common complication in patients before and after liver transplantation (LT). The aim of this study was to investigate the efficacy of prophylactic treatment with bisphosphonates after LT in preventing progressive bone loss in LT patients. We included 136 patients with end-stage liver diseases awaiting LT. Bone mineral density (BMD) (by dual X-ray absorptiometry) and markers of bone metabolism were determined before, and 4, 12, 24, 36, and 48 months after LT. All patients received vitamin D and calcium supplementation before and after LT, those with osteopenia or osteoporosis prior to LT were additionally treated with alendronate following LT. Decreased BMD was seen in a high percentage of patients undergoing LT (osteopenia 48.5%, osteoporosis 23.5%). Reduced BMD before LT was not related to gender, underlying liver disease, or Child-Turcotte-Pugh classification. Body mass index (BMI) prior to LT, however, correlated significantly with the fracture risk. Alendronate prevented the ubiquitously observed bone loss after LT in patients with osteoporosis and osteopenia and, in addition, led to an increase in BMD in patients with osteoporosis within 24 months after LT. In conclusion, our study suggests that alendronate is efficacious in preventing the natural course of bone loss associated with LT.

Glucocorticoid-induced osteoporosis: from basic mechanisms to clinical aspects

Glucocorticoid (GC)-induced osteoporosis (GCOP) is the most common cause of osteoporosis in adults aged 20-45 years as well as the most common cause of iatrogenic osteoporosis. GC excess, either endogenous or exogenous, induces bone loss in 30-50% of cases. Indeed, bone loss leading to fractures is perhaps the most incapacitating, sometimes partially irreversible, complication of GC therapy. Nevertheless, GCOP is often underdiagnosed and left untreated. The following article provides an update on the cellular and molecular mechanisms implicated in the pathophysiology of GC-induced bone loss, as well as some guidelines on diagnostic, preventive and therapeutic strategies for this medical condition, in an effort to promote a better knowledge and greater awareness of GCOP by both the patient and the physician.

Prevention and therapy of osteoporosis: the roles of plain vitamin D and alfacalcidol

Severe vitamin D deficiency was identified only in the first decades of the last century as the most common aetiology of rickets in children and osteomalacia in adults. It was later shown that vitamin D is not, as had been supposed, the biologically active principle for healing bone disease but must be hydroxylated in the liver and then finally in the kidney to become 1alpha,25-dihydroxy-cholecalciferol, a biologically highly active renal hormone. This study reviews the various principles, mechanisms, and approaches to the treatment of different forms of osteoporosis using vitamin D, alfacalcidol, and calcitriol therapy regimens.

Efficacy of alphacalcidol and calcitriol in primary and corticosteroid-induced osteoporosis: a meta-analysis of their effects on bone mineral density and fracture rate

Vitamin D metabolites alphacalcidol and calcitriol (D-hormones) have been investigated for two decades, but few and conflicting results are available from high-quality randomized controlled trials. Our objectives were to provide an evidence-based update quantitatively summarizing their efficacy on bone mineral density (BMD) and fracture rate. We performed a systematic research of any randomized controlled trial containing relevant data, peer review, data extraction and quality scoring blinded for authors and data sources, and comprehensive meta-analyses of the relevant data. Inclusion criteria were: randomized controlled study, calcitriol or alphacalcidol, BMD or fractures in healthy/osteopenic/osteoporotic patients exposed or not to corticosteroids (CS). Analyses were performed in a conservative fashion using professional dedicated softwares and stratified by outcome, target patients, study quality, and control-group type. Results were expressed as effect size (ES) for bone loss or relative risk (RR) for fracture while allocated to D-hormones vs control. Publication bias and robustness were investigated. Of the trials that were retrieved and subsequently reviewed, 17 papers fitted the inclusion criteria and were assessed. Quality scores ranged from 20 to 100%, the mean (standard deviation) being 72 (22)%. Calcitriol and alphacalcidol were found to have the same efficacy on all outcomes at p>0.13. We globally assessed D-hormones effects in preventing bone loss in patients not exposed to CS, and found positive effect: ES=0.39 ( p<0.001). For lumbar spine, this particular effect was 0.43 ( p<0.001). D-hormones significantly reduced the overall fracture rates: RR=0.52 (0.46; 0.59) and both vertebral and non-vertebral fractures: RR=0.53 (0.47; 0.60) and RR=0.34 (0.16; 0.71), respectively. No statistical difference in response was observed between results from studies on healthy and osteoporotic patients or depending on the fact that controls were allowed to calcium supplementation. Treatment with D-hormones was evaluated for maintaining spinal bone mass in five trials of patients with CS-induced osteoporosis, and provided ES=0.43 at p<0.001. Only two studies specifically addressed the effects of calcitriol on spinal fracture rate. None of them provided significant results, and the global RR did not reach the significance level as well: RR=0.33 (0.07; 1.51). Our data demonstrated efficacy for DH on bone loss and fracture prevention in patients not exposed to CS and on bone loss in patients exposed to CS, in the light of the most reliable scientific evidence. Their efficacy in reducing the number of fractures in patients exposed to CS remains to be determined.

DXA scanning

The steady improvement in densitometric technique is reviewed in this paper culminating in the newest generation of DXA scanners. The suitability of the lumbar spine, femur and hand as sites for the densitometric measurement of bone loss in rheumatoid disease is assessed. The recent improvement in hand scanning technique using DXA has led to improved clinical utility in the detection of juxta-articular bone loss. The enhanced resolution offered by the newest, solid state detector DXA scanners, and their ability to detect bone loss where no systemic features are evident, makes it possible that DXA scanning of the hand will be a useful modality for the monitoring of early rheumatoid disease.

Alendronate treatment for osteoporosis: a review of the clinical evidence

Bisphosphonates have recently gained an increasing role in the management of osteoporosis. The aminobisphosphonate, alendronate has recently been introduced as a new agent for the treatment of postmenopausal osteoporosis. This paper reviews the clinical evidence for the use of this agent and seeks to assess its place in osteoporosis management.