What are the comparative efficacies of alendronate and etidronate in the treatment of osteoporosis?

There are several studies that compare the efficacy of alendronate and etidronate in the treatment of osteoporosis. In these studies, alendronate appears to be superior to etidronate in its ability to inhibit bone resorption.

Beauchesne and Miller compared the efficacy of etidronate and alendronate in a prospective, randomized, double-blind, placebo-controlled clinical trial.¹ The authors mention that no studies have directly compared the efficacy of these two agents, and the results of long-term clinical trials have not been published. Based on the results obtained in clinical trials to date using fractures as an end point, alendronate appears to be the bisphosphonate of choice. However, safety profiles and cost should also be considered when choosing between etidronate and alendronate for the treatment of postmenopausal osteoporosis.

Watts and Becker conducted a multicenter study to determine the response to alendronate therapy in women with postmenopausal osteoporosis who were non-responders to intermittent cyclical etidronate therapy.² The prospective observational study recruited twenty-five women from a university out-patient clinic specializing in the treatment of osteoporosis. Measurements included in the study were bone mineral density of the lumbar spine and proximal femur. Women who were non-responders changed therapy from etidronate to alendronate 10 mg/day, which they received for greater than one year. Bone mineral density increased significantly at the lumbar spine (p<0.0001) and at all hip sites. Changes in bone markers suggest that alendronate causes a more complete suppression of bone resorption and less inhibition of bone formation.

Fairney and colleagues performed a study to determine whether pretreatment with etidronate affected the response to alendronate and whether patients who did not respond to etidronate responded to alendronate.³ After two years of therapy with alendronate 10 mg/day, there was a significant increase in lumbar spine bone mass density compared with baseline (p<0.0001). In 10 patients who were previously taking etidronate and switched to alendronate, there was a significantly better response (p<0.002) in the lumbar spine. Fifteen patients who had no improvement at the femoral neck taking etidronate therapy demonstrated a significant improvement (p<0.004) with alendronate therapy. This study demonstrated that alendronate produces a greater bone density response than etidronate.

In conclusion, alendronate appears to be more efficacious than etidronate in the treatment of osteoporosis. However, cost, adverse effect profile, and potential drug interactions should be considered when selecting an agent.

References:

1. Beauchesne MF and Miller PF. Etidronate and alendronate in the treatment of postmenopausal osteoporosis. Ann Pharmacother 1999; 33: 587-99.
2. Watts NB and Becker P. Alendronate increases spine and hip bone mineral density in women with postmenopausal osteoporosis who failed to respond to intermittent cyclical etidronate. Bone 1999; 24: 65-68.
3. Fairney A, Kyd P, Thomas E, Wilson J. Response to alendronate in osteoporosis after previous treatment with etidronate. Osteoporos Int 2000; 11: 621-25.
4. Sato M, Bryant HU, Iversen P, et al. Advantages of raloxifene over alendronate or estrogen on nonreproductive and reproductive tissues in the long-term dosing of ovariectomized rats. J Pharmacol Exp Ther 1996; 279: 298-305.