Persistence with oral bisphosphonates and denosumab among older adults in primary care in Ireland

Abstract

Purpose: Gaps in pharmacological treatment for osteoporosis can reduce effectiveness. This study aimed to estimate persistence rates for oral bisphosphonates and denosumab in older primary care patients and identify factors associated with discontinuation. Methods: Older patients newly prescribed oral bisphosphonates or denosumab between 2012 and 2017 were identified from 44 general practices (GP) in Ireland. Persistence without a coverage gap of >90 days was calculated for both medications from therapy initiation. Factors associated with time to discontinuation were explored using Cox regression analysis. Exposures included age-group, osteoporosis diagnosis, fracture history, calcium/vitamin D prescription, number of other medications, health cover, dosing frequency (bisphosphonates) and previous bone-health medication (denosumab). Results: Of 41,901 patients, n=1,569 newly initiated on oral bisphosphonates and n=1,615 on denosumab. Two-year persistence was 49.4% for oral bisphosphonates and 53.8% for denosumab and <10% were switched to other medication. Having state-funded health cover was associated with a lower hazard of discontinuation for both oral bisphosphonates (HR=0.49, 95%CI=0.36-0.66, p<0.01) and denosumab (HR=0.71, 95%CI=0.57-0.89, p<0.01). Older age-group, number of medications and calcium/vitamin D prescription were also associated with better bisphosphonate persistence while having osteoporosis diagnosed was associated with better denosumab persistence. Conclusion: Persistence for osteoporosis medications is sub-optimal. Of concern, few patients are switched to other bone-health treatments when denosumab is stopped which could increase fracture risk. Free access to GP services and medications may have resulted in better medication persistence in this cohort. Future research should explore prescribing choices in primary-care osteoporosis management and evaluate cost-effectiveness of interventions for improving persistence.