Effects of intravenous pamidronate therapy on Paget's disease of bone.

Pamidronate is a second generation bisphosphonate that has been used in Europe for the treatment of Paget's disease of bone for several years. It relieves pain and reduces bone turnover in Paget's disease. To assess the effects of pamidronate on Paget's disease of bone, the authors treated 28 patients, aged 45 to 87, with longstanding Paget's disease for a period of 4-18 months. Parameters measured included pain and serum alkaline phosphatase, urinary hydroxyproline, and ionized calcium concentrations. Patients were organized into two groups. Patients in the first group had initial alkaline phosphatase concentrations below 215 U/L, which decreased to normal after one dose of pamidronate. Patients in this group also experienced symptomatic improvement. Patients in the second group had initial alkaline phosphatase values greater than 240 U/L, which did not normalize after 2-11 pamidronate infusions. More patients in this latter group did not report symptomatic improvement. Patients in the second group also had a higher incidence of hypocalcemia. It is concluded that there is a clear relation between initial alkaline phosphatase level in Paget's disease and response to treatment with pamidronate. The authors' current protocol for treating patients with pamidronate is based on this relation. Because pamidronate proved most effective when used in mild Paget's disease, therapy probably should be instituted early in the course of disease.