Pamidronate infusions for the treatment of Paget's disease of bone.

Effective pamidronate dosages in Paget's disease of bone have not yet been determined. We prospectively compared two pamidronate dosages (60 mg and 120 mg) in 26 patients whose baseline alkaline phosphatase level was at least two-fold the upper limit of normal. Pamidronate was given as three-hour infusions of 60 mg each. Follow-up was two years. The two groups were comparable at baseline except for higher alkaline phosphatase and hydroxyproline levels in the group treated with 120 mg pamidronate. Efficacy on laboratory parameters was greater in the higher dosage group. Osteocalcin levels showed little change. In both dosage groups, alkaline phosphatase levels fell significantly versus baseline, and the difference persisted throughout the two-year follow-up. Urinary hydroxyproline excretion remained significantly reduced versus baseline during the first 12 months and rose subsequently. A return to normal of the two study parameters six months after treatment was associated with longer duration of the biologic treatment response. A survival curve analysis confirmed this finding and suggested that a return to normal of laboratory parameters was predictive of clinical remission. The drug was well tolerated. Adverse effects were mild and similar to those recorded during earlier studies.