Relationship Between Gastrointestinal Events and Compliance With Osteoporosis Therapy: An Administrative Claims Analysis of the US Managed Care Population.

Purpose: A large proportion of women with osteoporosis do not comply with current osteoporosis therapies, resulting in diminished therapeutic effect. Noncompliance may be due to the occurrence of gastrointestinal (GI) events during the course of therapy. The objective of this study was to estimate the rate of GI events among women taking oral bisphosphonates and to determine the association between GI events and compliance with bisphosphonate therapy.

Methods: This was a retrospective analysis of data from a US Medicare claims database (HUMANA). The study period was from January 2007 to June 2013. The index date was the date of the first oral bisphosphonate prescription (alendronate, ibandronate, or risedronate) occurring between January 2008 and June 2012. The pre- and postindex periods were the 1-year periods before and after the index date, respectively. The analysis included women 65 years of age and older who were naïve to all osteoporosis treatments before the index date. GI events included nausea/vomiting; dysphagia; esophagitis; esophageal reflux; esophageal, gastric, duodenal, and peptic ulcer; stricture, perforation, or hemorrhage of the esophagus; acute gastritis; and GI hemorrhage. GI events were assessed during the preindex period and at 3, 6, and 12 months in the postindex period. Compliance was defined as a medication possession ratio of ≥80%. The medication possession ratio was calculated as the total days׳ supply of bisphosphonate in the postindex period divided by 365 days. The association of postindex GI events with compliance was assessed using multivariate logistic regression.

Findings: The analysis included 37,886 women initiating oral bisphosphonate therapy. In the preindex year, 37.5% of the women experienced a GI event, and in the postindex year, 38.9% had a GI event. Patients with preindex GI events had numerically higher rates of postindex GI events than patients without preindex GI events (61.8% vs 25.1% at 12 months postindex). Patients who experienced postindex GI events were less likely to be compliant with bisphosphonate therapy, with odds of compliance of 0.76 (95% CI, 0.72-0.80) after 12 months.

Implications: Among US women who were prescribed oral bisphosphonates, on-treatment GI events were associated with decreased compliance at 1 year.