Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement

The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.

Switching the Dose Regimen of Oral Bisphosphonates, Adherence and Fractures

Briesacher¹, Becky, Andrade², Susan, Harrold¹, Leslie R., Fouayzi², Hassan, Yood³, Robert A.

Univ of Massachusetts Med Schl, Worcester, MA,
Meyers Primary Care Institute, Worcester, MA,
Fallon Clinic, Worcester, MA

Purpose:

To assess adherence and fracture risk in patients who switch dose regimens of oral bisphosphonates.

Method:

This is a population-based interrupted times-series analysis using a nationwide administrative health data from 2003–2006. We identified 1835 switchers of once-weekly to once-monthly oral bisphosphonates and matched them to two comparators using propensity-score methodology: switchers of different once-weekly oral bisphosphonates, and nonswitchers assigned a random switch. We measured adequate adherence as a monthly medication possession ratio >/=0.80 and calculated monthly incidence rate ratios [IRR] of osteoporotic fractures. We tested for pre- and post-switch differences in adherence and fractures rates.

Results:

All study groups experienced considerable attrition in adherence: 1 year post-switch, the proportion of adequate adherers was 41% regimen switchers, 47% drug only switchers, and 37% nonswitchers. The regimen switch was associated with decelerated nonadherence (absolute change in monthly attrition rate, -4% pre-switch vs. -1% post-switch, p<.000). There were no significant changes in nonadherence for nonswitchers (absolute change in monthly attrition rate, -4% pre-switch vs. -2% post-switch, p=.578) or drug only switchers (-1% pre-switch vs. -1% post-switch, p=.745). The regimen switch was not associated with reduced fracture risk: 1 year post-switch, the incidence risk ratios for regimen switchers relative to drug only switchers were 0.85, 95% CI 0.52–1.36, and 0.92, 95% CI 0.56–1.58, relative to nonswitchers).

Conclusion:

Reducing the dosing demands of oral bisphosphonates from once-weekly to once-monthly decelerated but did not halt adherence failure. The regimen change did not translate to reduced fracture risk.

To cite this abstract, please use the following information:
Briesacher, Becky, Andrade, Susan, Harrold, Leslie R., Fouayzi, Hassan, Yood, Robert A.; Switching the Dose Regimen of Oral Bisphosphonates, Adherence and Fractures [abstract]. Arthritis Rheum 2009;60 Suppl 10 :861
DOI: 10.1002/art.25941

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