PAMIDRONATE DISODIUM IN PAGETS-DISEASE OF BONE

Paget's disease of bone is a relatively common disorder in some countr ies, though virtually unknown in others. Its aetiopathology remains un elucidated, but a viral infection may be involved. The primary biochem ical indicators are increased urinary hydroxyproline excretion (relate d to bone resorption) and elevated serum alkaline phosphatase levels ( related to new bone production); changes in these values are the most widely used measures of response to treatment. Pamidronate has been us ed to treat Paget's disease of bone since the late 1970s. Administrati on may be orally, though poor absorption of the drug in the gut leads to low bioavailability, or by intravenous infusion: both routes are as sociated with good clinical response. The choice of an optimal dose an d intravenous administration regime is still a matter for debate; comp lex regimes involving multiple infusions over several weeks have been shown to produce up to 90% remission rates, but single dose procedures , usually with relatively high doses, are also effective in producing long-term remission. Pamidronate treatment is accompanied by radiologi cal evidence of arrest or reversal of bone lesions, and improved bone texture. Treatment efficacy has also been indicated by improvement or normalization of bone scans. Patients with severe Paget's disease of b one, and patients whose disease has proved refractory to other treatme nt (calcitonin or etidronate, or both of these combined) also generall y respond well to treatment with pamidronate. The primary determinant of response to pamidronate treatment, and also of remission rate and d uration, is the pretreatment severity of disease: this is correlated w ith the initial response to treatment with pamidronate, refractoriness to other treatments, and pretreatment biochemical indices. It is conc luded that, on the basis of available evidence, pamidronate is the tre atment of first choice for Paget's disease of bone, but that further w ork is needed to elucidate the optimal intravenous dose and administra tion regimen.