DRUGS USED IN THE TREATMENT OF METABOLIC BONE-DISEASE - CLINICAL-PHARMACOLOGY AND THERAPEUTIC USE

Osteoporosis is the most important metabolic bone disease and places a n increasing burden on the healthcare system. The condition can be pre vented by the early introduction of hormone replacement therapy. The r ole 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 subs tantial bone loss is accompanied by architectural disintegration. Repl acing lost bone may not necessarily restore mechanical integrity and p rotect against fractures. The management of Paget's disease has been q uite revolutionised by the introduction of the bisphosphonates. The co ndition is a result of a primary increase in osteoclastic bone resorpt ion which can be corrected by bisphosphonates, with considerable sympt omatic improvement. The increasing potency and safety margin of the ne wer agents has meant that the threshold for treatment has fallen. Ther e is now potential for long term control of bone turnover with the hop e of preventing late complications. Hypercalcaemia of malignancy is us ually the result of both increased bone destruction and decreased urin ary calcium excretion. These two components of hypercalcaemia demand d ifferent approaches to management. The general availability of an ever -expanding range of increasingly potent bisphosphonates has resulted i n 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 calciu m load derived from increased bone destruction. Calcitonin is the only agent which is currently available to counter this process.