European Consensus Statement on the diagnosis and management of osteoporosis in chronic kidney disease stages G4-G5D

Controlling the excessive fracture burden in patients with chronic kidney disease (CKD) Stages G4-G5D remains an impressive challenge. The reasons are 2-fold. First, the pathophysiology of bone fragility in patients with CKD G4-G5D is complex and multifaceted, comprising a mixture of age-related (primary male/postmenopausal), drug-induced and CKD-related bone abnormalities. Second, our current armamentarium of osteoporosis medications has not been developed for, or adequately studied in patients with CKD G4-G5D, partly related to difficulties in diagnosing osteoporosis in this specific setting and fear of complications. Doubts about the optimal diagnostic and therapeutic approach fuel inertia in daily clinical practice. The scope of the present consensus paper is to review and update the assessment and diagnosis of osteoporosis in patients with CKD G4-G5D and to discuss the therapeutic interventions available and the manner in which these can be used to develop management strategies for the prevention of fragility fracture. As such, it aims to stimulate a cohesive approach to the management of osteoporosis in patients with CKD G4-G5D to replace current variations in care and treatment nihilism.

Bisphosphonates in Dialysis and Transplantation Patients: Efficacy and Safety Issues

Bisphosphonates are an old class of compounds. They were used in the 1930s as antiscaling and anticorrosion agents in washing powders and water to prevent the deposition of calcium crystals. Those basic functions were later utilized in an attempt to prevent ectopic calcifications in humans. The early studies demonstrated that bisphosphonates had a strong affinity for bone. That property was first exploited when the compounds were used for “bone scans.”

Currently, the drugs are used for treatment of hypercalcemic conditions, abnormal bone remodelling, Paget disease, malignancy, and osteoporosis. Bisphosphonates have several important toxicities: acute renal failure, worsening renal function, reduced bone mineralization, and osteomalacia. For those reasons and others, this class of drugs has not yet been approved for use in children or in patients with severe renal insufficiency.

The present review covers several aspects of bisphosphonates: molecular structure, routes of administration, pharmacology, mechanisms of action, toxicities, and exceptional uses in children with renal disease.

Pharmacokinetics/pharmacodynamics of bisphosphonates: use for optimisation of intermittent therapy for osteoporosis

Bisphosphonates suppress osteoclast-mediated bone resorption and are widely used in the management of osteoporosis. Daily oral administration of alendronic acid and risedronic acid have been shown to reduce the risk of vertebral and non-vertebral fractures. Once-weekly regimens with these bisphosphonates are pharmacologically equivalent to daily regimens. Regimens with treatment-free intervals longer than 1 week present an attractive therapeutic option as they may offer additional patient convenience and long-term adherence to treatment. However, until recently, such regimens, usually referred to as intermittent or cyclical, have not shown any convincing antifracture efficacy in clinical trials, probably because of the empirical manner in which the design of these regimens has been approached. Investigation of pharmacokinetics/pharmacodynamics of bisphosphonates may help in the design of effective intermittent dosage regimens. Bisphosphonates are poorly absorbed from the gastrointestinal tract and about 50% of the absorbed drug is taken up selectively by the skeleton, while the rest is excreted unaltered in urine. Bisphosphonates exert their action at the bone surface, where they are taken up by the osteoclasts during bone resorption. Therefore, when describing the pharmacokinetics of bisphosphonates in relation to the pharmacodynamics, the amount of bisphosphonate at the skeleton should be accounted for. Few of the reported clinical pharmacokinetic studies addressed this issue. This is partly due to the absence of study design elements to account for skeletal binding of the drugs. Pharmacokinetic studies have also been hampered by technical difficulties in determining the concentration of bisphosphonates in serum and urine. Moreover, most clinical pharmacokinetic (but also pharmacokinetic/pharmacodynamic) studies have primarily used noncompartmental analysis, leaving out the distinct advantages of modelling and simulation techniques. Clinically, the primary action of bisphosphonates can be assessed by the measurement of biochemical markers of bone resorption. Recent studies indicate that the pattern of these markers during bisphosphonate treatment may be predictive of antifracture efficacy; however, only limited data are available for the development of pharmacokinetic/pharmacodynamic models that are able to predict the response of these markers to different treatment regimens with bisphosphonates. Recently, pharmacokinetic/pharmacodynamic models for response to bisphosphonates have been described and, at present, some of them are being used in the design of bisphosphonate regimens with long drug-free intervals.

Bone mineral density in multiple myeloma patients after intravenous clodronate therapy

Bisphosphonates inhibit osteoclastic bone destruction that may be stimulated by myeloma cells. By this way, bisphosphonates carry the potential to lower the number of new pathological fractures, of hypercalcaemic events, and of intensity of bone pain as was published earlier. Clodronate has been administered orally in most clinical studies so far despite of its poor bioavailability from the gastrointestinal tract. The aim of our study was to evaluate bone mineral density (BMD) changes in 34 newly diagnosed multiple myeloma patients regularly treated by 900 mg of clodronate in slow intravenous infusions on an outpatient basis in two-week intervals for at least 24 months. BMD was evaluated by CT scanning every six months. Initial values of trabecular BMD were only about 60 per cent of age- and sex-adjusted healthy population values. Clodronate therapy seemed to preserve BMD within the period of two or three years. This effect was seen not only in patients responding to chemotherapy but even in the small subgroup of patients with persisting active disease. We conclude that the long-term intravenous clodronate therapy may contribute to the preservation of BMD and thus calcium hydroxyapatite in bones in multiple myeloma patients concomitantly treated by chemotherapy. The administration of clodronate should start early in the course of disease, before BMD has been markedly reduced.