Background: In previous studies, the choice of doses of tranexamic acid was empirically defined as no pharmacokinetic study had been conducted in haemorrhagic caesarean section.
Objective: The objective was to build a pharmacokinetic model in patients receiving a single 0.5, 1 or 2 g intravenous bolus.
Method: A preliminary monocentric open study was performed in the Lille centre. Blood samples and one urinary sample were collected in the 6 h following the injection. Nine patients were included. Tranexamic acid concentration was measured using liquid chromatography system coupled with tandem mass spectrometry. We used Monolix 2019R1 for population pharmacokinetic modelling. A structural model was constructed followed by the investigation of potential covariates.
Results: Data were best described with a two-compartment model with a double first-order elimination from the central compartment. The model was improved when the variable ideal weight per dose was affected as a covariate for the apparent volume of distribution. Assuming a dose of 1 g and a height of 160 cm, the pharmacokinetic parameters were estimated at 10.26 L.h-1 for total clearance, 11.5 L for the volume of the central compartment, 15.8 L for the volume of the second compartment, a diffusional clearance of 30.36 L.h-1 , and a urinary excretion fraction of 25.8%.
Conclusions: The population pharmacokinetic model of tranexamic acid in haemorrhagic caesarean section was successfully established in our tiny sample of patients. The results of this preliminary TRACES pharmacokinetic study suggested that elimination of tranexamic acid is partially non urinary in contrast with healthy patients.
Keywords: Caesarean section; Intravenous; Pharmacokinetics; Postpartum haemorrhage; Tranexamic acid.
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