Bisphosphonate resistance in Paget's disease of bone.
OBJECTIVE
To determine whether resistance to one bisphosphonate predicts resistance to another bisphosphonate.


METHODS
One hundred patients with Paget's disease were treated with intravenous (IV) pamidronate. The initial dose was 120 mg, followed by further doses of 240 mg, until either biochemical remission was achieved or a total dose of 1 gm was given. Biochemical remission was defined as an alkaline phosphatase level within the reference range. Patients whose disease failed to respond to pamidronate were then treated with alendronate for 6 months. Patients whose disease failed to respond to alendronate were given either tiludronate for 3 months, or clodronate for 6 months.


RESULTS
Sixteen of the 100 patients treated with pamidronate failed to achieve a biochemical response despite a cumulative dose of 1 gm. Of the 16 nonresponders, 1 died of an unrelated cause, and the remaining 15 patients were treated with alendronate. In 2 of these patients, the treatment was changed to another bisphosphonate because of gastrointestinal intolerance to alendronate. Of the remaining 13 patients, 9 (69%) achieved full biochemical remission. In 4 other patients, both pamidronate and alendronate therapy were unsuccessful (1 patient responded to tiludronate, tiludronate therapy was unsuccessful in 1, clodronate was unsuccessful in 1, and 1 patient elected to receive no further treatment). Of the 2 patients who could not receive alendronate because of gastrointestinal intolerance, 1 achieved normalization with tiludronate, and a repeat course of pamidronate was unsuccessful in the other. In total, 73% of patients in whom initial treatment with IV pamidronate was unsuccessful responded to a change in bisphosphonate treatment.


CONCLUSIONS
Failure to achieve biochemical normalization is likely to be specific to the individual drug rather than indicative of bisphosphonate class resistance.
Joshua
Fred
F
Royal Newcastle Hospital, Pacific Street, Newcastle, New South Wales 2300, Australia.
Epstein
Martin
M
Major
Gabor
G
D000368:Aged; D000369:Aged, 80 and over; D019386:Alendronate / Q000008:administration & dosage; D000469:Alkaline Phosphatase / Q000032:analysis; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage*; D004002:Clodronic Acid / Q000008:administration & dosage; D004164:Diphosphonates / Q000008:administration & dosage*; D004351:Drug Resistance; D006801:Humans; D007275:Injections, Intravenous; D008875:Middle Aged; D010001:Osteitis Deformans / Q000188:drug therapy*; D000077268:Pamidronate
D000893:Anti-Inflammatory Agents; D004164:Diphosphonates; D004002:Clodronic Acid; C058651:tiludronic acid; D000469:Alkaline Phosphatase; D000077268:Pamidronate; D019386:Alendronate