The analgesic effect of pamidronate is not caused by the elevation of beta endorphin level in Paget's disease--a controlled pilot study.

INTRODUCTION: Although an analgesic effect is an essential component of the mode of action of bisphosphonates, its physiological mechanisms are still unclear. Beta-endorphin release plays an important role in the analgesic effect of both calcitonin and raloxifene. As patients with Paget's disease receive large doses of bisphosphonates within relatively short time periods, we examined whether repeated pamidronate infusion therapy would cause measurable change in beta-endorphin levels

MATERIALS & METHODS: Visual analog scale (VAS) scores of pain intensity, beta-endorphin levels, and alkaline phosphatase activity of 11 patients with Paget's disease (7 with the mono- and 4 with the polyostotic form) were determined at baseline, as well as after 3 and 6 infusions (on Days 6 and 12 of treatment, respectively). Eleven untreated patients with Paget's disease (7 with the mono- and 4 with the polyostotic form) served as controls.

RESULTS: It was established that in the course of pamidronate infusion therapy BE levels remained constant, whereas the values in serum alkaline phosphatase and pain intensity scores were significantly reduced.

CONCLUSIONS: Although high-dose pamidronate therapy does mitigate pain substantially (as demonstrated by the reduction of VAS scores), its analgesic action is probably unrelated to the enhancement of beta-endorphin release.