The effect of intrauterine administration of prostacyclin on the contractility of the non-pregnant uterus in vivo.

Prostacyclin was infused into the uterus of non-pregnant women either during early menstruation or in the secretory phase of the cycle. A dose of 5 micrograms/min produced little systemic effect and caused a significant decrease in uterine activity on Days 1 and 2 of the menses whereas 0.5 microgram/min did not. However, when dysmenorrhoeic pain and increased uterine activity were produced by infusion of PGF2 alpha during the secretory phase, PGI2 neither decreased the activity nor the pain. This indicates that PGI2 does not cause uterine relaxation by blocking the action of PGF2 alpha.