Inhibitory effect on bone formation and calcification exerted by the anti-inflammatory drug ibuprofen. An experimental study on adult rat with fracture.

The anti-inflammatory drug ibuprofen (2-(4-isobutylfenyl)propionic acid) was administered to adult male rats for 10 weeks in daily oral doses of 16 mg. Fractured and unfractured tibias were studied during 4 to 10 weeks' treatment by the use of microradiography, fluorescence labelling and biochemistry. New bone formation was observed to be inhibited on endosteal surfaces of the tibia when treated with ibuprofen, which also diminished the amount of cortical bone (almost significantly). However, the bone area and the new bone formation of periosteal callus and on periosteal surfaces of tibia was not influenced by the treatment. The chemical composition of fractured and unfractured bone was significantly altered and showed a reduced ratio of hydroxyproline/nitrogen as well as an inhibition of calcification of bone matrix with a reduced calcium/nitrogen ratio followed by an increased ratio of hexosamine/DNA and RNA-ribose/DNA after treatment with ibuprofen. The inhibition of new bone formation and calcification of bone in adult rat exerted by ibuprofen may be explained as a direct effect on bone-forming cells on endosteal bone surfaces.