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Bisphosphonates are stable analogues of pyrophosphate which bind to, and stabilise,
bone by inhibiting osteoclastic activity. Bisphosphonates may also directly
stimulate formation of bone by osteoblasts (1).
The main indications for bisphosphonates are:
- Paget's disease of bone
- hypercalcaemia of malignancy
- osteoporosis
Bisphosphonates are poorly absorbed after oral ingestion. Further impairment
to absorption is caused by food, drinks and drugs containing magnesium, calcium,
iron or aluminium salts.
A proportion of bisphosphonate that are absorbed is taken up by, and incorporated
into, bone while the remaining fraction is excreted unchanged by the kidneys.
Bisphosphonates that have been taken up and incorporated into the skeleton are
then only released when the bone is resorbed during turnover.
Reference:
- Drugs and Therapeutics Bulletin (2001), 39 (9), 68-72.
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