THE CIRCULATING LEVELS OF OXYTOCIN FOLLOWING INTRAVENOUS AND INTRAMUSCULAR ADMINISTRATION OF SYNTOMETRINE

Abstract

Summary Using a radioinimunoassay for oxytocin, circulating levels of the hormone were measured following intravenous and intramuscular administration of Syntometrine. After intramuscular injection oxytocin appeared in the circulation in as little as 30 seconds and continued to be detectable at levels around 25 pg. per ml. for up to 60 minutes. After intravenous injection there was a rapid rise to a peak of 530 pg. per ml. at one minute. The subsequent decay showed a bi‐exponential pattern, and yielded an average half‐life of 3 minutes for the initial rapid phase of disappearance. Following subcutaneous injection of Syntometrine, circulating oxytocin was found in only one of the two cases studied. After intravenous ergometrine, there was no detectable rise in oxytocin levels.