The effects of metergoline combined with PGF2 alpha treatment on luteal function and gestation in pregnant bitches.
1995
Gerstenberg C. | Nothling J.O.
This study was designed to determine the nature of the antiluteotrophic effect of metergoline on pregnant bitches, the occurrence of clinically evident side-effects, and the efficacy of PGF2alpha in initiating abortion after a course of metergoline therapy. Starting on Days 18 to 20 after the onset of diestrus, 8 adult pregnant beagle bitches were treated twice daily with 0.4 to 0.5 mg/kg po metergoline for 5 d. After receiving no treatment for the next 5 d, metergoline administration was repeated for a further 3 d, followed by twice-daily intramuscular injections of dinoprost tromethamine at 250 microgram/kg. There was an overall trend for the plasma progesterone concentration to decrease during the first and second course of metergoline therapy and to rise during the intervening period of no treatment. None of the bitches aborted during or after the first 5 d of metergoline administration. No side-effects were evident during the metergoline therapy. After pretreatment with metergoline a mean of 4.8 injections of PGF2alpha was necessary to ensure complete abortion. All abortions were rapid and uneventful, except for the usual side-effects associated with PGF2alpha. The plasma progesterone concentration at the onset of PGF2alpha treatment was positively correlated to the number of PGF2alpha injections needed to complete the abortion process. The plasma progesterone concentration was < 8 nmol/l for several days as a result of metergoline therapy in 6 of the 8 bitches. Only 1 bitch, however, aborted before PGF2alpha therapy was initiated. In the other 7 bitches PGF2alpha appeared to be necessary for abortion. The results suggest that the effect of metergoline has to be considered incompletely luteolytic at the doses used in this study. Even prolonged suppression of luteal function in early to mid-gestation, however, did not cause abortion without the previously documented luteolytic and/or ecbolic effects of PGF2alpha.
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