Antifertility effect of the implant containing 16-methylene-17 alpha-acetoxy-19-norprogesterone (ST-1435)
Abstract
The silastic capsules containing ST-1435 (0.5, 1, 2, 4, 6 or 8 mg) showed "burst effect" with a peak value of 4-15 micrograms.h-1 after incubation in vitro. A constant release rate was gradually approached within 1-2 wk. After the capsules were subcutaneous implanted or vaginally administrated, the rats manifested diestrus within 24-48 h. The normal estrus cycles and fertility were restored as soon as the release rate of implants decreased to 10 micrograms.d-1 in vitro. ST-1435 did not inhibit the superovulation induced by PMSG and HCG in immature female rats, but blocked the ovulation induced by LHRH in mature rats.
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