A Cochrane review included 11 RCTs involving a total of 2635 women . Use of carbetocin (a long-acting synthetic oxytocin analogue) resulted in a reduction in the need for therapeutic uterotonic agent for those who underwent caesarean section (RR 0.62, 95% CI 0.44 to 0.88; 4 trials, n=1173 ) compared to oxytocin , but not for vaginal delivery (1 trial). Carbetocin also reduced the need for uterine massage in both caesarean and vaginal deliveries (RR 0.54, 95% CI 0.37 to 0.79; 2 trials, n=739 and RR 0.70, 95% CI 0.51 to 0.94; 1 trial, n=160 respectively). There was a trend towards a lower risk of postpartum haemorrhage (PPH) with carbetocin compared to oxytocin for participants who underwent caesarean delivery (RR 0.55; 95% CI 0.31 to 0.95; 3 low quality trials, n=820) but not in vaginal delivery.
Comparison between carbetocin and syntometrine showed a lower mean blood loss in women who received carbetocin compared to syntometrine (mean difference (MD) -48.84 ml; 95% CI -94.82 to -2.85; 4 trials, n=1030). There was no statistically significant difference in terms of the need for therapeutic uterotonic agents, but the risk of adverse effects were lower in the carbetocin group: nausea (RR 0.24; 95% CI 0.15 to 0.40; 4 trials, n=1030); vomiting (RR 0.21; 95% CI 0.11 to 0.39; 4 trials, n=1030).
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment, inadequate intention-to-treat adherence), by imprecise results (few patients and wide confidence intervals), and by possible publication bias (pharmaceutical company sponsored trials).