SummaryWe conducted a study to assess pharmacokinetics of high-dose tranexamic acid for 24 h after administration of the drug in patients undergoing cardiac surgery with cardiopulmonary bypass. High-dose tranexamic acid involved a bolus of 30 mg.kg )1 infused over 15 min followed by a 16 mg.kg.h )1 infusion until chest closure with a 2 mg.kg )1 load within the pump prime. Tranexamic acid followed first-order kinetics best described using a two-compartment model, with a total body clearance that approximated the glomerular filtration rate. Mean plasma tranexamic acid concentrations during the intra-operative period and in the first 6 postoperative hours were consistently higher than the suggested threshold to achieve 100% inhibition and 80% inhibition of tissue plasminogen activator. With recent studies implicating high-dose tranexamic acid as a possible aetiology of postoperative seizures following cardiac surgery, the minimum effective yet safe dose of tranexamic acid in high-risk cardiac surgery needs to be refined. Tranexamic acid, a synthetic antifibrinolytic, is a lysine derivative that competitively inhibits the activation of plasminogen, thereby reducing the conversion of plasminogen to plasmin, an enzyme that degrades fibrin clots, fibrinogen, and other plasma proteins, including the procoagulant factors V and VIII [1]. At higher doses, tranexamic acid directly inhibits plasmin activity [2][3][4][5]. Tranexamic acid thus inhibits fibrinolysis, a putative mechanism of bleeding after cardiopulmonary bypass (CPB) [6]. Hence, this compound is routinely used during cardiac surgery procedures involving CPB, to reduce blood loss [1][2][3][4][5]. Tranexamic acid is considered to have a good safety profile. However, this has been challenged recently as several studies have found an association between high-dose tranexamic acid administration and an increased incidence in postoperative