Objective: To compare the efficacy and safety of tiludronate and etidronate at the same dosage (400 mg/day) for the treatment of active Paget's disease of bone.
Methods: We studied 234 patients with radiologic lesions characteristic of Paget's disease of bone and serum alkaline phosphatase (AP) concentrations at least twice the upper limit of normal, in a prospective, randomized, double-blind, multicenter clinical trial lasting 6 months. Patients were randomly allocated into 1 of 3 treatment groups: tiludronate for 3 months followed by placebo for 3 months, tiludronate for 6 months, or etidronate for 6 months. Serum AP levels and urinary hydroxyproline excretion were measured at baseline and after 3 months and 6 months. Patients with a reduction of at least 50% in the serum AP concentration were considered to be responders.
Results: After 3 months, the proportion of responders was higher in the tiludronate group (57.4%) than in the etidronate group (13.9%) (P < 0.0001). In the etidronate group, this percentage was lower among patients who had received previous treatment with a bisphosphonate (2.3%) than among those who had not (28.6%) (P < 0.01). Previous bisphosphonate treatment was not associated with response in the tiludronate group. After 6 months, the proportion of responders did not differ between the 2 tiludronate groups (60.3% and 70.1%), but was lower in the etidronate group (25.3%) (P < 0.0001). There was a higher proportion of patients with treatment-resistant disease (< 25% reduction of serum AP) in the etidronate group (51.9%) than in the tiludronate 3-month group (17.9%) or the tiludronate 6-month group (19.5%) (P < 0.0001). Gastrointestinal disturbances were more common, and occurred earlier, with tiludronate, but they were mostly mild, requiring no treatment.
Conclusion: Tiludronate at 400 mg/day for 3 months or 6 months is more effective than the same dosage of etidronate for 6 months in the treatment of Paget's disease.