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Alendronate has been shown to increase bone mineral density (BMD) and decrease fracture risk in postmenopausal women with osteoporosis, but the need for long-term treatment is unclear, especially because alendronate is incorporated in bone matrix and has a biological half-life of more than 10 years. In this study, a total of 1099 postmenopausal women (mean age, 73) — who had taken alendronate for at least 5 years in a previous clinical trial — were randomized to continued treatment (either 5 or 10 mg/day) or placebo. All participants also took 500 mg/day of calcium and 250 U/day of vitamin D.
After 5 additional years of follow-up, BMD (total hip, femoral neck, trochanter, or lumbar spine) was roughly 2%–3% greater in both alendronate groups than in the placebo group, although BMD in the placebo group was slightly higher than at the start of the previous trial 10 years earlier. Biochemical markers for bone turnover increased to a statistically greater extent in the placebo group than in either alendronate group. There were no differences between groups in the rate of nonvertebral fractures, but symptomatic vertebral fractures were significantly less common in the alendronate group than in the placebo group (2.4% vs. 5.3%).
Black DM et al. Effects of continuing or stopping alendronate after 5 years of treatment: The Fracture Intervention Trial Long-term Extension (FLEX): A randomized trial. JAMA 2006 Dec 27; 296:2927-38.
Comment
These “glass half-full, half-empty” results suggest that women at low risk for fracture may feel comfortable taking a break after 5 years of alendronate treatment. Other women, particularly those with prior fractures or very low bone density, may choose to continue.