Promethazine inhibits osteoclastic bone resorption in vitro
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Updated: Oct 21, 2026

A Novel in vivo Gene Transfer Technique and in vitro Cell Based Assays for the Study of Bone Loss in Musculoskeletal Disorders
Published on: June 8, 2014
1Ciba-Geigy Ltd., Research Department, Basel, Switzerland.
Abstract:
Several studies have shown that promethazine can reduce age-related osteopenia in mice. Furthermore, prolonged treatment with promethazine (50 mg/day) increases bone mineral content in the lumbar spine in post-menopausal women with osteopenia. However, the mechanism of action of promethazine has not been elucidated. The present study shows that promethazine HCl (0.01-10 microM) dose-dependently inhibits bone resorption by isolated rat osteoclasts in the bone slice assay with an IC50 of approximately 1 microM. Since these concentrations are likely to be achieved in vivo, it is suggested that the beneficial effect of promethazine on osteopenia is at least partly due to a direct inhibitory effect on osteoclast activity.
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