Intravenous tranexamic acid concentrations between 10 mg/L and 15 mg/L appear to result in substantial inhibition of fibrinolysis, and concentrations between 5 mg/L and 10 mg/L may be partly inhibitory, according to a study published in Blood Coagulation & Fibrinolysis.

Researchers investigated the minimal concentration of tranexamic acid needed in the blood to inhibit fibrinolysis in an effort to determine whether different routes of administration may be possible in settings where intravenous injection is not possible. They conducted a systematic review of tranexamic acid pharmacodynamics studies conducted prior to November 2017. The search included all in vitro or in vivo studies involving the relationship between tranexamic acid blood or plasma concentrations and any reliable measure of fibrinolysis.

A total of 21 studies (20 in vitro and 1 in vivo) were included. One clinical trial measured tranexamic acid levels and fibrinolysis in surgical patients’ blood and 4 studies employed clotting models or fibrin plates. In 16 of the 20 in vitro studies, tranexamic acid was added to blood or plasma drawn from healthy volunteers or commercial sources.

The authors concluded that tranexamic acid concentrations of 10 mg/L to 15 mg/L may be suitable targets for pharmacokinetic studies. However, tranexamic acid concentrations above 5 mg/L may also be effective.

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These findings may inform future pharmacokinetic studies investigating the bioavailability of tranexamic acid through subcutaneous, oral, or intramuscular administration, the researchers noted. They further theorized that achieving therapeutic levels of tranexamic acid via alternative routes could pave the way for prehospital management of patients with trauma and postpartum hemorrhage.

Reference

1. Picetti R, Shakur-Still H, Medcalf RL et al. What concentration of tranexamic acid is needed to inhibit fibrinolysis? A systematic review of pharmacodynamics studies [published online January 9, 2019]. Blood Coagul Fibrinolysis. doi: 10.1097/MBC.0000000000000789