EFFECT OF FLUNIXIN MEGLUMINE ON ENDOGENOUS PROSTAGLANDIN-F2-ALPHA SECRETION DURING CLOPROSTENOL INDUCED-ABORTION IN MARES

Objective-To determine the relative role of endogenous prostaglandin F -2 alpha (PGF(2 alpha) secretion in cloprostenol-induced abortion in m ares that no longer require luteal progesterone secretion for maintena nce of pregnancy, and to evaluate the ability of a prostaglandin cyclo oxygenase inhibitor (flunixin meglumine) to prevent cloprostenol-induc ed abortion. Design-The effect of flunixin meglumine on PGF(2 alpha) S ecretion and outcome of pregnancy was compared between mares treated w ith cloprostenol only and mares treated with cloprostenol plus flunixi n meglumine. Animals-Five pregnant mares, aged 4 to 15 years, of light -horse type. Procedure-Cloprostenol (250 mu g) was administered at 24- hour intervals to 5 pregnant mares. Flunixin meglumine (500 mg, IV) wa s administered at 8-hour intervals starting 15 minutes before the firs t cloprostenol administration. Hourly blood samples were analyzed for 15-ketodihydro-PGF(2 alpha) progesterone, and estrogen concentrations. Previously reported data on cloprostenol-induced abortion in 6 pregna nt mares treated daily with cloprostenol only were used as historic co ntrols. Results-The mean (+/- SEM) interval from first cloprostenol ad ministration to fetal expulsion 56.4 (+/- 13.7) hours and number of cl oprostenol administrations 3.2 (+/- 0.6) in the 5 flunixin meglumine-t reated mares were not significantly different, compared with values fo r 6 pregnant mares treated daily with cloprostenol only, 48.6 (+/- 5.6 ) hours and 2.8 (+/- 0.2) cloprostenol administrations. Flunixin meglu mine did not inhibit endogenous PGF(2 alpha) secretion. Prostaglandin F-2 alpha secretion rates on the day before and day of fetal expulsion were similar in both groups. Conclusion-Flunixin meglumine at a dosag e of 500 mg/animal, administered IV every 8 hours, is ineffective in m odulating uterine PGF(2 alpha) secretion during cloprostenol-induced a bortion. Clinical Relevance-Flunixin meglumine is ineffective in the m odulation of prostaglandin-induced uterine PGF(2 alpha) secretion and, therefore, does not offer a viable alternative for the prevention of abortion in mares at risk of abortion because of systemic illness.