Effect of promethazine on double tetracycline bone labeling in old mice.

Twenty-five-month-old female B6AF1 mice were injected intramuscularly (i.m.) with declomycin (75 mg/kg) 50 days and 2 days, or 20 days and 2 days, before sacrifice, and cross-sections of their femoral shafts were examined quantitatively for areas of tetracycline fluorescence. Two groups of mice received promethazine HCl in their drinking water (12 mg/dl) for 1 year, and the control groups were untreated. It was found that: the number of discrete areas of cortical and endosteal tetracycline deposition was increased slightly in the groups given promethazine; the length of the endosteal and cortical tetracycline deposits were 2-3 times greater, respectively, in the promethazine treated groups; and the distance between the cortical tetracycline deposits and the endosteum was 2.5 times greater in the promethazine groups. These results support the view that net bone deposition in osteopenic old mice is enhanced by promethazine.