Effect of oral misoprostol, alone or in combination with aglepristone, on mid-term pregnancy termination in cats

This study aimed to determine the efficacy and safety of oral misoprostol (MIS) administration in the induction of mid-term pregnancy termination in cats.

Twenty-eight cats that were pregnant for 30-40 days were allocated to four groups. The aglepristone (AGL) group (n = 7) received 10 mg/kg SC aglepristone q24h for two consecutive days. In the AGL+MIS group (n = 7), AGL (as administered in the AGL group) and MIS (200 µg/cat PO q12h until the start of abortion) were administered. The MIS200 (n = 7) and MIS400 groups (n = 7) received MIS (200 or 400 µg/cat misoprostol, respectively) alone PO q12h until the start of abortion. Blood samples were collected at the start of treatment (d0), 4 days after the start of treatment (d4) and on the day of complete abortion/end of administration (dA/d7).

The efficacy of the treatment was 71.4% in the AGL group, 100% in the AGL+MIS group, 0% in MIS200 group and 57.4% in MIS400 group (P = 0.004). No significance was found in relation to the interval from treatment to the start/end of abortion and the duration of abortion in all groups. The most observed side effect was vomiting in both groups administered MIS, particularly in the MIS400 group (56.7%). Progesterone (P4) concentrations were reduced during the abortion, but not to basal levels, in all groups. P4 concentrations were significantly lower at dA/d7 in the MIS400 group compared with the AGL and AGL+MIS groups (P = 0.002).

The results obtained from this study showed that low doses of MIS do not induce abortions in cats but increase the effect of AGL. Although higher doses could terminate pregnancies, this also causes intense unwanted side effects. Therefore, the use of MIS alone as an abortifacient in cats is not recommended. For mid-term pregnancy termination in cats, the combination of misoprostol and aglepristone provides a more effective abortifacient than using either of them alone.