Exploring cardiac effects after oxytocin 2.5 IU or carbetocin 100 µg: A randomised controlled trial in women undergoing planned caesarean delivery.

BACKGROUND: Oxytocin can stimulate release of myocardial biomarkers troponin I and T, prolong QTc and induce ST-depression. OBJECTIVE: To explore cardiac changes after either intravenous carbetocin or oxytocin. STUDY DESIGN: Exploratory phase 4 randomised controlled trial. SETTING: Obstetrics units of Oslo University Hospital, Norway between September 2015 and May 2018. PARTICIPANTS: Forty healthy, singleton pregnant women aged 18 to 50 years at gestational age at least 36 weeks with a planned caesarean delivery. INTERVENTIONS: Participants were randomised to receive either oxytocin 2.5 IU or carbetocin 100 µg immediately after delivery. MAIN OUTCOME MEASURES: The primary endpoint was the assessment of troponin I within 48 h of study drug administration. Troponin I and T, and creatine kinase myocardial band assessments were measured before spinal anaesthesia (baseline), and again at 4, 10 and 24 h after delivery. QTc, ST-depression and relative increase in heart rate were recorded from start of study drug administration to 10 min after delivery. All adverse events were monitored. RESULTS: Compared with the carbetocin group, higher troponin I levels were observed in the oxytocin group at 4 h and 10 h after delivery. For both treatment groups, an increase from baseline in troponin I and T was most pronounced at 10 h after delivery, and it had begun to decline by 24 h. QTc increased with time after administration of both study drugs, with a mean maximum increase of 10.4 ms observed at 9 min (P   <  0.001). No statistical differences were observed in QTc ( P  = 0.13) or ST-depression ( P  = 0.11) between the treatment groups. CONCLUSIONS: Oxytocin 2.5 IU and carbetocin 100 µg caused a similar increase in QTc. The trial was underpowered with regards to ST-depression and the release of myocardial biomarkers and these warrant further investigation. Data from this trial will inform a larger phase 4 trial to determine potential drug differences in troponin release. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02528136.

A study protocol for the cardiac effects of a single dose of either oxytocin 2.5 IU or carbetocin 100 µg after caesarean delivery: a prospective randomized controlled multi-centre trial in Norway.

Background: Both oxytocin and carbetocin are used to prevent uterine atony and post-partum haemorrhage after caesarean delivery in many countries, including Norway. Oxytocin causes dose-dependent ST-depression, troponin release, prolongation of QT-time and arrythmia, but little is known about myocardial effects of carbetocin. We have previously demonstrated comparable vasodilatory effects of oxytocin and carbetocin and are now undertaking a Phase 4 trial to investigate whether carbetocin causes similar changes to myocardial markers compared with oxytocin. Methods: Our randomized controlled trial will be conducted at three obstetrics units at Oslo University Hospital and Akershus University Hospital, Norway. Planned enrolment will be of 240 healthy, singleton pregnant women aged 18 to 50 years undergoing planned caesarean delivery. Based on pilot study data, each participant will receive a one-minute intravenous injection of either oxytocin 2.5 IU or carbetocin 100 µg during caesarean delivery. The prespecified primary outcome is the change from baseline in high-sensitive troponin I plasma concentrations at 6-10 hours after study drug administration. Secondary outcomes include uterine tone grade at 2.5 and five minutes after study drug administration, adverse events for up to 48 hours after study drug administration, estimated blood loss within eight hours of delivery, need for rescue treatment and direct/indirect costs. Enrolment and primary analysis are expected to be completed by the end of 2021. Discussion: Women undergoing caesarean delivery should be assessed for cardiovascular risk particularly as women with an obstetric history of pregnancy induced hypertension, gestational diabetes mellitus, preterm birth, placental abruption, and stillbirth are at increased risk of future cardiovascular disease. Any additional ischaemic myocardial risk from uterotonic agents will need to be balanced with the benefit of reducing the risk of postpartum haemorrhage. Any potential cardiotoxicity difference between oxytocin and carbetocin will help inform treatment decisions for pregnant women. Registration: Clinicaltrials.gov NCT03899961 (02/04/2019).