The compatibility of oxytocin and tranexamic acid injection products
when mixed for co-administration by infusion for the treatment of
postpartum haemorrhage: an in vitro investigation
Abstract
Objective: To investigate the compatibility of oxytocin and tranexamic
acid injection products when mixed for the purpose of co-administration
by intravenous infusion. Population or Sample: Oxytocin and tranexamic
acid were collected from hospitals taking part in a multicentre
postpartum haemorrhage treatment (E-MOTIVE) trial in Kenya, Nigeria,
Tanzania, and South Africa. Methods: The compatibility of two sentinel
products of oxytocin injection and tranexamic acid injection in 200mL
infusion bags of both 0.9%w/v saline and Ringer’s Lactate was assessed.
We analysed all tranexamic acid -oxytocin combinations, and each
evaluation was conducted for up to 6hrs. Subsequently, the compatibility
of multiple tranexamic acid products with reference oxytocins products
when mixed in 0.9%w/v saline over a period of 1 hour was investigated.
Results: We found a significant interaction between certain oxytocin and
tranexamic acid products after mixing them in vitro and observing for 1
hour. The interaction substantially impacted oxytocin content leading to
reduction in concentration (14.8% - 29.0%) immediately on mixing (t=0
minutes). In some combinations, the concentration continued to decline
throughout the stability assessment period. Oxytocin loss was observed
in 7 out of 22 (32%) combinations tested. Conclusions: In a clinical
setting, mixing oxytocin and tranexamic acid may result in an
underdosing of oxytocin, compromising care in an emergency
life-threatening situation. The mixing of oxytocin and tranexamic acid
injection products for co-administration with IV infusion fluids should
be avoided until the exact nature of the interaction and its
implications are understood.