Absorption of the oral bisphosphonate alendronate in osteoporotic patients with Crohn's disease

The absorption of bisphosphonates from the gut is poor. The question arises whether the absorption of alendronate, and thus its bioavailability, is further altered by the local inflammatory process in patients with Crohn’s disease, thereby potentially affecting clinical outcome when used in the treatment of osteoporosis. To address this question, urinary excretion of alendronate was evaluated 3 months and 6 months after start of treatment with oral alendronate at a dose of 10 mg/day in 19 osteoporotic patients with stable Crohn’s disease, 12 of whom had an intestinal resection. Biochemical parameters of bone turnover and BMD were also measured at start and at 6 months. Thirteen patients had been previously treated with glucocorticoids and five were currently using them. The average 24-h urinary excretion of alendronate was 0.5–0.6% of the dose administered, a figure comparable to that reported for osteoporotic patients without gut pathology. There was a significant decrease from baseline in urine N-telopeptides of collagen cross-links (NTx)/creatinine (60%) associated with an increase in lumbar spine BMD of already 2% after 6 months of treatment. Our data suggest that in patients with Crohn’s disease, alendronate is adequately absorbed from the intestine and retained in the skeleton. This adequacy is confirmed by appropriate suppression of bone resorption and increase in lumbar spine BMD. These data hold significant implications for the clinical management of patients with Crohn’s disease and osteoporosis.