Patients at high risk of fracture usually have low bone mineral density (BMD) and a history of prior osteoporotic fracture. The risk of fracture increases as BMD decreases.1, 2, 3 In patients at high risk of fracture, osteoporosis treatment requires a rapid response and a strong increase in BMD. Anabolic drugs that promote osteogenesis and potentially enhance bone quality are a therapeutic option for patients who have osteoporosis and are at high risk of fracture.4, 5, 6 Teriparatide is an anabolic drug that consists of the N-terminal fragment (1–34) of parathyroid hormone (PTH). When administered intermittently, it increases bone formation in patients with osteoporosis. Daily subcutaneous administration of teriparatide, known as daily teriparatide (D-TPTD), promotes bone formation, enhances bone density, and lowers the risk of both vertebral and non-vertebral fractures in individuals with osteoporosis.7, 8, 9, 10 Another formulation of teriparatide is injected subcutaneously twice a week (TW-TPTD) and can increase BMD in the lumbar spine.11, 12, 13

Adherence and persistence are important for improving the effectiveness of therapeutic agents. The reasons for poor adherence and persistence are numerous, including drug tolerability, dosage of therapeutic agents, and motivation.14 A previous report showed that patients preferred the monthly bisphosphonate regimen over weekly bisphosphonate.15 Other studies have showed that patients receiving monthly bisphosphonates had higher persistence than those receiving daily or weekly bisphosphonates.16,17 Adherence over 1 year was 38.6, 70.6, and 77.7% for daily, weekly, and monthly bisphosphonates, respectively (P<0.001).16 Similarly, adherence to monthly administration of biological disease-modifying antirheumatic drugs for rheumatoid treatment was higher than that of weekly or every 2 weeks administration.18,19

Studies on the effect of the dosing regimen of teriparatide on adherence and persistence are lacking. We hypothesized that differences in the dosing regimen of D-TPTD and TW-TPTD might affect adherence. Therefore, this study was performed to analyze and compare adherence, persistence, and BMD changes for D-TPTD and TW-TPTD.