| THE EXPECTED RESPONSE to specific drug therapy is an increase in bone
mass over one to two years, followed by stabilisation.
If significant bone loss ( > 5%-6% of lumbar spine per year)
continues despite the institution of a standard therapy for
osteoporosis, several steps should be followed:
- Scrutinise serial bone density scans to ensure that they are
technically comparable, that the same vertebrae have been assessed
and that there have not been changes in vertebral dimensions, scan
outlines, software or the instrument used for analysis.
- If the bone loss is thought to be real, then assess patient
compliance. Is the patient actually taking the medication? How often
are tablets being missed? Oral bisphosphonate therapy must be taken
fasting with water and temporally separated from any form of mineral
supplement or its bioavailability can be markedly reduced.
Biochemical markers of bone turnover (serum levels of osteocalcin or
bone-specific alkaline phosphatase, and urinary hydroxyproline or
pyridinoline secretion) may be useful in the assessment of
compliance, as suppressed values should be found with treatments
such as bisphosphonates and oestrogens. Non-compliance may be
attributable to side effects and so require changes in the dose or
preparation used.
- In any patient not responding as expected to osteoporosis therapy,
the possibility of some other underlying disease should be
considered. The patient should be screened again for underlying
causes of osteoporosis (e.g., multiple myeloma, coeliac disease,
vitamin D deficiency). Very low calcium intake should also be
excluded.
- If bone loss is occurring despite compliance and the lack of other
causes, the dose of therapy should be reviewed. Some early
postmenopausal women require doses greater than the equivalent of
625µg of conjugated equine oestrogens or 50µg/day of
transdermal oestradiol to maintain bone mass. This may be a
particular problem for women who smoke. In patients taking hormone
replacement therapy who do not have oestrogenic side effects and who
are losing bone density, a 50%-100% increment in dose should be
considered. In those who have problems with intestinal absorption, a
change in route of administration should be considered. Trial
evidence with the potent bisphosphonates suggests that significant
loss of bone is very uncommon in those taking tablets as instructed.
- In patients in whom bone loss is taking place despite optimal dosing
of a single agent, specialist referral for advice is appropriate.
Next: How can people suffering from osteoporosis-related injury and disability best be managed and rehabilitated?
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