Effect of flunixin meglumine on endogenous prostaglandin F2α secretion during cloprostenol-induced abortion in mares

Abstract

Abstract Objective To determine the relative role of endogenous prostaglandin F2α (pgf2α secretion in cloprostenol-induced abortion in mares that no longer require luteal progesterone secretion for maintenance of pregnancy, and to evaluate the ability of a prostaglandin cyclooxygenase inhibitor (flunixin meglumine) to prevent cloprostenol-induced abortion. Design The effect of flunixin meglumine on pgf2α secretion and outcome of pregnancy was compared between mares treated with cloprostenol only and mares treated with cloprostenol plus flunixin meglumine. Animals Five pregnant mares, aged 4 to 15 years, of light-horse type. Procedure Cloprostenol (250 μg) was administered at 24-hour intervals to 5 pregnant mares. Flunixin meglumine (500 mg, iv) was administered at 8-hour intervals starting 15 minutes before the first cloprostenol administration. Hourly blood samples were analyzed for 15-ke-todihydro-pgf2α, progesterone, and estrogen concentrations. Previously reported data on cloprostenol-induced abortion in 6 pregnant mares treated daily with cloprostenol only were used as historic controls. Results The mean (± sem) interval from first cloprostenol administration to fetal expulsion 56.4 (± 13.7) hours and number of cloprostenol administrations 3.2 (± 0.6) in the 5 flunixin meglumine-treated mares were not significantly different, compared with values for 6 pregnant mares treated daily with cloprostenol only, 48.6 (± 5.6) hours and 2.8 (± 0.2) cloprostenol administrations. Flunixin meglumine did not inhibit endogenous pgf2α secretion. Prostaglandin F2α secretion rates on the day before and day of fetal expulsion were similar in both groups. Conclusion Flunixin meglumine at a dosage of 500 mg/animal, administered iv every 8 hours, is ineffective in modulating uterine pgf2α secretion during cloprostenol-induced abortion. Clinical Relevance Flunixin meglumine is ineffective in the modulation of prostaglandin-induced uterine pgf2αsecretion and, therefore, does not offer a viable alternative for the prevention of abortion in mares at risk of abortion because of systemic illness.