[Effect of oral biphosphonates in patients with cystic fibrosis and low bone mineral density]

Abstract

Disturbances in bone mineralization are frequent in cystic fibrosis but few studies have focused on the use of biphosphonates in this indication, and none on the use of oral etidronate. We report our experience using this latter treatment.

Methods: The study was retrospective and included five children and three adults with cystic fibrosis (six males and two females) aged seven to 30 years with Z-scores for lumbar bone density lower than -2 SD after one year of calcium (1 g/day) and vitamin D (900 UI/day and 300,000 UI/6 months) supplementation. All were treated during one year with etidronate: four courses of 15 days (one course per trimester) with doses ranging from 4 to 8 mg/kg per day. Calcium and vitamin D supplementation was continued between the etidronate treatment course. Total body and lumbar bone mineral density (BMD) were measured three times: at the beginning and the end of the year of calcium and vitamin D supplementation and at the end of the year of supplementation plus the four courses of etidronate treatment.

Results: The increase in BMD in absolute value (g/cm2) and in Z-score was significantly higher (P <0.05) after the year of combined supplementation and etidronate treatment (total body g/cm2: 3+/-1%, Z-score: 2+/-1% and lumbar spine g/cm2: 6+/-5%, Z-score: 3+/-4%) than after supplementation alone (total body g/cm2: -1+/-3%, Z-score: -4+/-3% and lumbar spine g/cm2: -1+/-3%, Z-score: -4+/-4%). Supplementation alone improved the total BMD in only one patient and the lumbar BMD in three, whereas after etidronate treatment the total and lumbar BMD were improved in the eight patients. None of the patients presented with side effects that could be attributed to the treatment.

Conclusion: Oral etidronate treatment is well-tolerated and capable of improving bone mineralization in patients with cystic fibrosis. Further work will be necessary to determine the optimal dosage and the optimal frequency for the treatment series.