INHIBITION OF FRACTURE-HEALING BY INDOMETHACIN IN RATS

Abstract. The effect of indomethacin (2 mg/kg/day) on the healing of closed unimmobilized femoral fractures was examined in rats. A standard femoral fracture was produced in 205 male adolescent rats, and three different experiments were done. In a long‐term experiment, the rats were treated with either indomethacin or placebo for 29 days and fracture healing followed for a maximum of 91 days. In two short‐term experiments, the rats were treated with either indomethacin or placebo for a week and followed for a maximum of 122 days. The effect of age was studied in one experiment. Indomethacin plasma levels were about 1 μg/ml in the indomethacin‐treated animals. In the long‐term experiment, indomethacin inhibited fracture healing (P< 0·006) and increased the angulation between the femur fragments. In the short‐term experiments indo‐methacin inhibited fracture healing (P< 0·033) and increased the interfragmentary angle as well as fracture instability. All untreated fractures healed within 10 weeks in younger rats (210 g), whereas only 44% healed in older rats (295 g). Copyright © 1979, Wiley Blackwell. All rights reserved