INDOMETHACIN AND UTERINE EVACUATION OF CONCEPTUS IN RATS - POSSIBLE MODE OF ACTION

Indomethacin at a dose of 2.5 mg/kg from day 18 through day 20 of pregnancy was found to extend the duration of gestation for 2-3 days over the control value. Conversely, prostaglandin F2α (PGF2α) at a dose of 2.0 mg/kg on day 18 of pregnancy induced premature parturition. PGF2a given concurrently with indomethacin resulted in neutralisation of the drug action and the animals delivered viable pups as identically recorded in controls. Failure of indomethacin to extend the length of pseudopregnancy in either bilaterally hysterectomized or bilaterally decidualized pseudopregnant rats revealed that the lenthening of the duration of pregnancy caused by indomethacin is not due to an extension of luteal span, but results from relaxation of the uterine smooth musculature. © 1979.