Association between gastrointestinal events and compliance with osteoporosis therapy

PURPOSE The aim of this study was to estimate the rate of gastrointestinal (GI) events, and association between GI events and compliance with osteoporosis therapy among osteoporotic women. METHODS A retrospective cohort study using a large administrative claims database in the United States from 2001 through 2010 was conducted. We studied women ≥ 55 years old who were continuously enrolled in a health plan for at least 2 years, a baseline year before and a follow-up year after the date of the first prescription of oral bisphosphonate as the first oral osteoporosis treatment. Compliance with osteoporosis therapy was measured using the medication possession ratio (MPR), with compliance defined as MPR ≥ 0.8. Multivariate logistic regression was used to assess the association between occurrence of GI events and compliance with osteoporosis therapy after controlling for demographic and clinical characteristics. RESULTS A sample consisting of 75,593 women taking at least one oral bisphosphonate with mean (SD) age of 64 (8) years was identified. A total of 21,142 (28%) patients experienced at least one GI event during the follow-up period. Only 31,306 (41%) patients were compliant with osteoporosis therapy. Patients who experienced GI events after initiation of oral bisphosphonates were 29% less likely to adhere to osteoporosis therapy as compared to patients who did not experience GI events (odds ratio [95% CI], 0.71 [0.69-0.74]; P < .001). CONCLUSIONS Less than half of the patients were compliant with osteoporosis therapy within one year after initiating oral bisphosphonates, and the likelihood of compliance was significantly lower by 29% among women with GI events.