Bone Abstracts

Zoledronic acid has been shown to reduce the risk of fractures and improve bone mineral density (BMD) in osteoporosis vs placebo. This study compared changes in BMD in patients with osteoporosis treated with zoledronic acid vs alendronate. BMD at the lumbar spine and total hip pre- and post-bisphosphonate were recorded for 65 patients with osteoporosis (T score ≤−2.5) from retrospective analysis of DEXA scans. 35 patients received annual 5 mg IV zoledronic acid infusions over 3 years; 30 patients received 70 mg once weekly oral alendronate over mean duration of 3 years. Data were analysed using Mann-Whitney-tests in Minitab 15 statistical software. The number of fragility fractures post-bisphosphonate was recorded as was the reason for choosing zoledronic acid over alendronate.

The median percentage improvement in lumbar spine BMD with zoledronic acid was 5.5% (Interquartile range (IQR) −0.2 to 9.1%) and with alendronate was 6.45% (IQR 1.8 to 10.4%). Whilst there was a trend towards greater improvement with alendronate compared to zoledronic acid, this was not statistically significant (P=0.43). The median percentage improvement in total hip BMD with zoledronic acid was 0.3% (IQR −2.3 to 6.4%) and with alendronate was 0.8% (IQR −2.7 to 3.4%). However, this did not reach statistical significance (P=0.37). 8 patients (23%) suffered fragility fractures post zoledronic acid compared to 11 (37%) post alendronate. However this was not statistically significant (odds ratio 0.5, 95% confidence interval 0.2 to 1.5, P=0.2). The most common reasons for prescribing zoledronic acid were oral bisphosphonate intolerance and fragility fractures/decreased BMD despite alendronate use. This study showed while both zoledronic acid and alendronate improved lumbar spine BMD, there was no statistically significant difference between them. Zoledronic acid use therefore in those who have failed to respond to alendronate is questionable; however it may be a reasonable alternative in those intolerant of oral alendronate.