Carbetocin at elective Cesarean delivery: a randomized controlled trial to determine the effective dose.

PURPOSE: The primary objective of our study was to determine the minimum intravenous dose of carbetocin required to produce adequate uterine contraction in 95% of women (effective dose [ED](95)) undergoing elective Cesarean delivery (CD).

METHODS: Eighty term pregnant women with low risk for postpartum hemorrhage (PPH) undergoing elective CD under spinal anesthesia were randomly allocated to receive carbetocin intravenously in doses of 80 μg, 90 μg, 100 μg, 110 μg, or 120 μg upon delivery. The consultant obstetrician evaluated the efficacy of the patient's uterine tone as satisfactory or unsatisfactory. In case of unsatisfactory uterine tone, additional uterotonics were administered as per routine institutional practice. Side effects were monitored during the study period. The main outcome measure was satisfactory uterine tone at two minutes after carbetocin administration.

RESULTS: Satisfactory uterine tone was obtained in 70 subjects (87%) within the dose range of 80-120 μg of carbetocin. It was not possible to calculate the ED(95) of carbetocin due to the even distribution of women with satisfactory uterine tone across all dose groups (P = 0.99). Similarly, the side effects were similar across all dose groups. There was a high overall incidence of hypotension (55%) following the administration of carbetocin.

CONCLUSIONS: In women at low risk for PPH undergoing elective CD, carbetocin doses of 80-120 μg are similarly effective. There is a high incidence of hypotension associated with carbetocin in these doses, and further studies with doses lower than 80 μg are warranted to assess the balance of efficacy and side effects. This trial was registered at www.clinicaltrials.gov (NCT01262742).