Disclosed is the unexpected finding that enantiomers of phenothiazines, preferably the (+) enantiomer of promethazine, are particularly effective in inhibiting the bone resorbing cells, osteoclasts, thus providing new uses and methods for reducing bone loss and, e.g., treating periodontitis and osteoporosis. The invention provides a range of such uses, methods, medicaments and associated compositions and kits.
