Risedronate dosing before breakfast compared with dosing later in the day in women with postmenopausal osteoporosis

Summary Two studies in postmenopausal women with osteoporosis provide information about the efficacy and safety of dosing oral risedronate 5 mg daily at a time other than before breakfast (i.e., 2 h before and 2 h after any food and drink other than plain water). A significant increase in lumbar spine BMD was observed for both treatment regimens in the two studies. However, smaller increases in lumbar spine BMD were observed with flexible dosing versus before-breakfast dosing. Geographic region, compliance, and consistency of dosing time appear to affect the amount of increase in BMD observed with flexible dosing. Introduction Two studies in postmenopausal women with osteoporosis provide additional information about the efficacy and safety of dosing oral risedronate 5 mg daily at a time other than before breakfast (i.e., 2 h before and 2 h after any food and drink other than plain water). Methods One study, flexible dosing, was a 6-month North American study in 730 patients randomized to before-breakfast dosing or flexible dosing later in the day. A second study, IMPACT, was a large ( N = 2382), 1-year multinational study in patients that chose their dosing regimen (before breakfast or later in the day). These studies were used to examine the bone mineral density (BMD) response with different dosing regimens. Results A significant increase in lumbar spine BMD was observed for both treatment regimens in the two studies. However, in both studies, the flexible dosing group had a smaller increase from baseline compared to the before-breakfast regimen (ratio of flexible dosing to before breakfast: flexible dosing study, 0.52; IMPACT study, 0.75). In addition, a relationship between geographic region and BMD response was observed with flexible dosing in both studies. Patients in the flexible dosing group who had greater dosing compliance (based on the number of times the bottle was opened) and consistency of dosing time (bottle opened within a 1.5-h window) had a greater increase in lumbar spine BMD. Conclusion Results of these two studies demonstrate that overall flexible dosing of risedronate leads to smaller BMD gains compared to before-breakfast dosing. This result may be due to poorer adherence to the flexible dosing instructions that may be more pronounced in patients in certain geographic regions. If patients cannot abide by before-breakfast dosing and flexible dosing is an approved option, one can expect suboptimal BMD results with flexible dosing.