Association between gastrointestinal events and persistence with osteoporosis therapy: analysis of administrative claims of a U.S. managed care population.
BACKGROUND
A large proportion of patients do not persist with osteoporosis (OP) therapy. Gastrointestinal (GI) events (e.g., gastroesophageal reflux disease and nausea/vomiting) are common among OP patients receiving OP therapy and may impact persistence with treatment.


OBJECTIVE
To examine the association of GI events and persistence with OP therapy.


METHODS
Using a large U.S. administrative claims database, we studied women aged ≥ 55 years who received oral bisphosphonate (BIS) as their first OP therapy from 2002-2009. The index date was the first pharmacy claim date recorded for oral BIS therapy; the baseline period was 12 months pre-index, and follow-up was 12 months post-index. Patients were considered persistent with therapy if they had continuous refills of the index drug class without additional drug therapy from a different drug class from the index date until the end of the follow-up period with no gaps in supply greater than 45 days. Discontinuation was defined as the first gap greater than 45 days during which there was no evidence of refills of OP medication. The association between post-treatment GI events and the risk of discontinuation or switching was modeled with Cox regression stratified by presence of baseline GI events and adjusted for baseline clinical and demographic characteristics.


RESULTS
Of the 75,593 women who met eligibility criteria, 59.9% discontinued BIS; 39.3% were persistent; and 0.5% switched to non-BIS. GI events were diagnosed in 20,073 patients (26.6%) during baseline and in 21,142 (28.0%) in the post-treatment period (12-month follow-up post-index). Patients with post-treatment GI diagnosis were 35.6% more likely to discontinue or switch treatment (HR = 1.356, 95% CI = 1.318-1.396) during the 12-month follow-up compared with those without post-treatment GI diagnosis. GI events that occurred closer to treatment discontinuation or switching were associated with a greater risk of discontinuation or switching: 37.9% (HR = 1.379, 95% CI = 1.338-1.421) for GI events within 6 months of discontinuation or switching and 45.6% (HR = 1.456, 95% CI = 1.408-1.505) for GI events within 3 months of discontinuation or switching.


CONCLUSIONS
Among women aged 55 years or older in a U.S. managed care population, post-treatment GI events were associated with a higher risk of discontinuation of oral BIS or switching to non-BIS.