Fracture healing in rats inhibited by locally administered indomethacin.

We studied the inhibitory effect of indomethacin on fracture healing in 135 young, male rats after oral administration compared with local application into the fracture. A closed mid-diaphyseal fracture of the left femur was performed in all the rats. The fractures were not immobilized. In one experiment, half of the animals received indomethacin via a stomach tube (2 mg/kg/day) for 10 days; the controls received only the vehicle. In another experiment, 0.5 mg of indomethacin, contained in a bioerodible polyorthoester gel, was injected into the fracture area in half the rats; in the controls, only the gel was injected. In both experiments, random animals were killed on Days 0, 5, 10, and 20. As assessed by radiographs and manual testing, the same inhibition of fracture healing was found regardless of whether indomethacin was given orally or locally. However, the amount of indomethacin that was applied locally was only one fourth of the total dose given orally; no indomethacin was detected in the serum.