Low Compliance with Bisphosphonate Therapy Reduces Treatment Benefit

Bisphosphonates are widely used to treat osteoporosis and reduce fracture risk. Low compliance is frequent. Researchers at the PHARMO Institute in the Netherlands studied the impact of non-compliance with bisphosphonate therapy on treatment benefit.

New female users of alendronate or risedronate between 1999-2004, aged >45 years were identified from PHARMO-RLS, including drug-dispensing and hospitalization data of >2 million residents of the Netherlands. Patients were followed until first hospitalisation for an osteoporotic fracture, death, or end of study period. Compliance with bisphosphonates during follow-up was measured over 90-day intervals using Medication Possession Ratio (MPR). The association between compliance and fracture risk was analysed using time-dependent Cox-regression. The study cohort included 8,822 new female bisphosphonate users, contributing in total 22,484 person-years of follow-up. During follow-up, 176 osteoporotic fractures occurred (excluding the first six months). Non-compliant bisphosphonate use was associated with a 45% increased fracture risk compared to compliant use (MPR >80%). Classifying compliance into five categories, fracture risk gradually increased with poorer compliance (p-value <0.05 for trend). A MPR <20% was associated with an 80% increased fracture risk compared to a MPR >90%. The researchers concluded that these results show a statistically significant association between level of compliance with bisphosphonates and level of fracture risk, emphasizing the importance of treatment compliance in obtaining maximal treatment benefit.(Source: Penning-van Beest FJ, Erkens JA, Olson M, Herings RM. Loss of treatment benefit due to low compliance with bisphosphonate therapy. Osteoporos Int. 2007 Sep 14; [Epub ahead of print] : October 2007)