Postpartum uterine response to oxytocin and carbetocin.

OBJECTIVE

To obtain quantitative data on uterine contractility postpartum and compare the response of intramuscular oxytocin to carbetocin.

STUDY DESIGN

A prospective study using an intrauterine pressure transducer (IUPT) to measure frequency, amplitude, and duration of contractions following the administration of either oxytocin (10 U) or carbetocin (30 microg).

RESULTS

The IUPT was tolerated by all subjects and generated useful data 90% of the time in most subjects (12/16). Both drugs generated hypertonic uterine activity with contractions of similar duration. However, carbetocin resulted in contractions of sustained higher amplitude and frequency and therefore higher uterine performance as expressed by Montevideo units. This uterotonic effect of carbetocin lasted for 3 hours.

CONCLUSION

IUPT monitoring generated quantitative data on postpartum uterine activity. When compared to high-dose oxytocin, a low dose of carbetocin has a more prolonged effect on uterine activity both in terms of a higher amplitude and frequency of contractions.