Antireproductive effect of a potent LHRH antagonist (Nal-Lys antagonist:antide) during early pregnancy in the rat

Abstract Effects of a potent third generation LHRH antagonist [Nal-Lys antagonist:antide] have been observed during the first half of pregnancy in rats. A daily dose of 40 μg or above, when administered from day 8 of pregnancy, suppressed serum progesterone levels within 48 h and by day 12 there was complete absence of live fetuses. Lower doses of antide (10–20 μg) reduced progesterone levels in circulation but were unable to induce abortion consistently in all treated rats. Administration of 150 or 300 μg of antide once on day 8 suppressed the progesterone levels within 24 h. Only a dose of 300 μg was effective in completely interfering with gestation by day 12 with no observable live fetuses.