Tranexamic Acid

Mechanism

Mechanism of Action

Tranexamic acid is a synthetic antifibrinolytic that acts by inhibiting the enzymatic dissolution of fibrin deposits that stabilize the local hemostatic clot in the spiral arteries of the uterine endometrium.

Endometrial Stabilization Mechanism

Women with idiopathic Abnormal Uterine Bleeding (AUB) have elevated intrauterine levels of tissue plasminogen activators, which prematurely dissolve local clots and prolong shedding hemorrhage. Tranexamic acid is a structural analogue of lysine that competitively binds to the lysine anchoring sites on the plasminogen molecule. This blocks the interaction of plasminogen with fibrin, preventing its transformation into active plasmin and locally stabilizing endometrial clots, reducing menstrual blood loss by more than 40-50% without altering the surrounding plasma factors.

Pharmacokinetics

Pharmacokinetics

• Routes of administration: Oral (for regular menorrhagia) and slow intravenous (for postpartum hemorrhage).
• Absorption: Bioavailability of 35-45% orally, which is not affected by concurrent feeding.
• Distribution: Excellent endometrial tissue diffusion, where it reaches rapid hemostatic therapeutic concentrations locally.
• Excretion: Altered drug eliminated exclusively by active renal filtration (> 95% of the dose excreted through urine in 24 hours). Requires dose reduction and rigorous monitoring in the presence of mild to moderate renal failure.
• Half-life (t_1/2): Approximately 2 to 3 hours after intravenous injection.

Indicators and dose

Indications

• First-line treatment of abnormal uterine bleeding or recurrent idiopathic menorrhagia in women of childbearing potential.
• Prevention and treatment of obstetric hemorrhage in the immediate postpartum (WOMAN trial protocol).

Dosage and Schemes

• Regular menstrual bleeding (Oral gynecological use): 1 g to 1.3 g orally every 8 hours (maximum dose 3.9 g per day) started only on the first day of heavy bleeding and continued for a strict maximum cumulative period of 5 days per menstrual cycle.
• Postpartum Hemorrhage (WOMAN Protocol): 1 g slow IV (diluted in 100 mL of saline solution, infused at a slow rate in an interval of no less than 10 minutes to avoid reflex hypotension) administered preferably in the first 3 hours after delivery; A second dose of 1 g IV may be repeated if bleeding continues after a 30-minute interval.

Pregnancy and Breastfeeding

FDA Category B. Crosses the placental barrier reaching umbilical cord levels similar to maternal levels. It is not associated with fetal teratogenicity in preclinical studies. Its use in pregnancy is reserved exclusively for the control of severe postpartum hemorrhage or retroplacental bleeding in the first and second trimester under specialist judgment. Compatible with breastfeeding safely.

Security

Contraindications

• Personal history or suspicion of underlying active venous or arterial thromboembolic disease (DVT, pulmonary embolism, stroke, myocardial infarction).
• Severe chronic renal failure with creatinine clearance Cl_Cr < 30 mL/min (extreme risk of accumulation).
• Presence of macroscopic hematuria originating in the upper urinary tract (risk of acute ureteral obstruction due to intraluminal coagulation).

Adverse Effects (ADR)

• Gastrointestinal: Mild crampy abdominal pain, nausea and transient osmotic diarrhea (mainly taken orally at high doses).
• Neurological (Rare): Generalized seizures of central origin after massive doses of rapid intravenous infusion.
• Transient visual disturbances: Blurred vision or chromatopsia (rare, discontinue the drug immediately).