Anti-nidatory effect of vaginally administered (Ala8,13, 18)-magainin II amide in the rhesus monkey.

The hypothesis that timed application of a potent anti-microbial, anti-tumor agent like magainin peptides can inhibit blastocyst implantation was examined in the present study using the rhesus monkey as the primate model. Incidence of pregnancy, vaginal bleeding patterns, serum levels of progesterone, estrogen and monkey chorionic gonadotropin were examined following vaginal administration of (Ala8,13,18)-magainin II amide, a synthetic analogue of magainin 2, via tampon during days 20 to 26 of mated cycles. Implantation occurred in two out of three animals following administration of 0.25 mg magainin, while administration of 0.5 mg (Ala8,13,18)-magainin II amide resulted in inhibition of implantation in all females with no change in lengths of treatment cycles, and subsequent cycles. It appears from the present study that, besides being a local microbicidal agent, intravaginal administration of (Ala(8,13,18))-magainin II amide is a potential anti-implantation strategy for intercepting pregnancy.