Carbetocin vs. Oxytocin: In-vitro Myometrial Contractions With and Without Oxytocin Pre-treatment

Overview

The purpose of this study is to compare the ability of an isolated sample of uterine muscle tissue (in a tissue bath) to contract in the presence of various drugs. The drugs studied–uterotonics–are typically used to contract the uterus when a pregnant patient continues to bleed after delivery. Oxytocin is an old standard, but seems to suffer from a desensitization phenomenon. Carbetocin, a similar drug, has recently been suggested to clinicians as a replacement for oxytocin directly after certain types of Cesarean section.

The investigators will be testing isolated uterine muscle samples after pre-treatment with oxytocin OR nothing (control) to increasing concentrations of oxytocin OR carbetocin. Contractile measures will be measured and compared between all groups. The investigators hypothesize that oxytocin pre-treatment will reduce contractions in both oxytocin- and carbetocin-induced contractions, and oxytocin and carbetocin will induce different patterns of contractions.

Study Type

  • Study Type: Interventional
  • Study Design
    • Allocation: Non-Randomized
    • Intervention Model: Parallel Assignment
    • Primary Purpose: Treatment
    • Masking: None (Open Label)
  • Study Primary Completion Date: March 2012

Detailed Description

Postpartum hemorrhage (PPH) is a major cause of maternal mortality and morbidity. In 80% cases of PPH, the primary cause is failure of the uterus to contract after delivery of the baby, which then requires further treatment of the mother with uterotonic drugs (drugs used to contract uterus and thus prevent bleeding).

Patients participating in this study will be asked to donate a very small sample of uterine tissue during Cesarean section, which will be tested in the laboratory for the ability to contract in response to the uterotonics oxytocin and carbetocin. We will seek to better understand the effects of these drugs by comparing their contractile capability in isolated uterine tissue.

Interventions

  • Drug: Oxytocin
    • Oxytocin, 10-10mol/L to 10-5mol/L; solution made in double-distilled autoclaved water and then tested in physiological salt solution.
  • Drug: Carbetocin
    • Carbetocin, 10-10mol/L to 10-5mol/L; solution made in double-distilled autoclaved water and then tested in physiological salt solution.

Arms, Groups and Cohorts

  • Active Comparator: No drug pre-treatment
    • A control sample from each patient (no uterotonic drug will be applied during pre-treatment) will be measured concurrently with samples pre-treated with oxytocin. Controls will undergo the same dose response of oxytocin or carbetocin after pre-treatment period as the groups given oxytocin for pre-treatment.
  • Active Comparator: Drug pre-treatment
    • A sample from each patient will be pre-treated with oxytocin 10-5mol/L. These samples will undergo the same dose response of oxytocin or carbetocin after pre-treatment period as the groups given no drug for pre-treatment (controls).

Clinical Trial Outcome Measures

Primary Measures

  • Amplitude of contraction
    • Time Frame: 6-8 hours

Secondary Measures

  • Integrated area under response curve (AUC)
    • Time Frame: 6-8 hours
  • Basal tone
    • Time Frame: 6-8 hours
  • Frequency of contraction
    • Time Frame: 6-8 hours

Participating in This Clinical Trial

Inclusion Criteria

  • Gestational age 37-41 weeks
  • Non-laboring patients, not exposed to exogenous oxytocin
  • Patients requiring primary or first repeat Cesarean section
  • Cesarean section under spinal anesthesia

Exclusion Criteria

  • Patients who require general anesthesia
  • Patient who had previous myometrial surgery or more than one previous Cesarean section
  • Patients with placental anomalies
  • Emergency Cesarean section in labor
  • Patients with multiple pregnancy (twins, etc.)

Gender Eligibility: Female

Minimum Age: N/A

Maximum Age: N/A

Are Healthy Volunteers Accepted: Accepts Healthy Volunteers

Investigator Details

  • Lead Sponsor
    • Samuel Lunenfeld Research Institute, Mount Sinai Hospital
  • Collaborator
    • University of Toronto
  • Provider of Information About this Clinical Study
    • Sponsor
  • Overall Official(s)
    • Mrinalini Balki, MD, Principal Investigator, MOUNT SINAI HOSPITAL

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