PIP: Dr. Arnold Gillespie (January 15, p.150) indicates that uterine contractions can be enhanced if oxytocin is given after previous exposure to prostaglandin E2 (PGE2). Brummer showed by in vitro experiments that after exposure to the PGE2, but not to the PGF2alpha, human myometrial strips exhibited an enhanced response to oxytocin. We report here preliminary results on the abortifacient effect of a combined treatment with PGF2alpha and oxytocin. The combined treatment, administered extraamniotically by means of a Foley catheter introduced between the fetal membranes and the uterine wall through the cervical canal, was given to 32 women admitted to the hospital for termination of midtrimester pregnancies. A dose of 0.5 mg PGF2alpha (Astra) was given hourly to 20 women. Higher doses (0.75-2.0 mg) were used if the uterine contractions were weak or lacking. 9 women received a mixture containing 0.5 mg of PGF2alpha and 1 I.U. of oxytocin, and 3 women received 3 I.U. of oxytocin alone. In the PGF2 alpha group of 20 patients, abortion was complete in 7 and incomplete in 10 cases. 3 failures were encountered. The trial was considered a failure if uterine contractions stopped in spite of continuous and increased dosage. In the group of 9 women who received a mixture of PGF2alpha and oxytocin, there was no failure. Abortion was complete in 5 and incomplete in 4 cases. Of the 3 women who received oxytocin only, 1 aborted and 2 failed. Uterine contractions were present in all 3 cases. The mean dose of PGF2alpha required for an abortion was 26.1 mg in the PG group, while that in the combined PGF2alpha and oxytocin group was 15.2 mg. 2 of 3 failures in the PG group were successfully treated with an intravenous oxytocin infusion (5 I.U./hour), which caused uterine contractions when PG had no further effect. Hysterotomy was needed in 1 case, where a bicornuate uterus was found at the operation. Extraamniotic oxytocin alone caused uterine contractions in all 3 cases included in the trial, although abortion was achieved in only 1 case. The 2 failures in the oxytocin group were treated with extraamniotic PG. In the total series of 32 cases, hysterotomy was not required in 31 (97%) if both PG and oxytocin were used. PGF2alpha and oxytocin have a contractile effect on the uterus in vivo during midtrimester. Whether the effects of these 2 drugs are additive or potentiative is now being studied.