Ethamsylate 250 mg, Tranexamic Acid 250 mg Tablets

Tranexamic acid is a synthetic lysine amino acid derivative, which diminishes the dissolution of hemostatic fibrin by plasmin. In the presence of tranexamic acid, the lysine receptor binding sites of plasmin for fibrin are occupied, preventing binding to fibrin monomers, thus preserving and stabilizing fibrin’s matrix structure.

The antifibrinolytic effects of tranexamic acid are mediated by reversible interactions at multiple binding sites within plasminogen. Native human plasminogen contains 4 to 5 lysine binding sites with low affinity for tranexamic acid (K d= 750 µmol/L) and 1 with high affinity (K d= 1.1 µmol/L). The high affinity lysine site of plasminogen is involved in its binding to fibrin. Saturation of the high affinity binding site with tranexamic acid displaces plasminogen from the surface of fibrin. Although plasmin may be formed by conformational changes in plasminogen, binding to and dissolution of the fibrin matrix is inhibited.

Absorption — After a single oral administration of 1300 mg of tranexamic acid tablets, the peak plasma concentration (C max) occurred at approximately 3 hours (T max). The absolute bioavailability of tranexamic acid tablets in women aged 18‑ 49 is approximately 45%. Following multiple oral doses (1300 mg tablets three times daily) administration of tranexamic acid tablets for 5 days, the mean C maxincreased by approximately 19% and the mean area under the plasma concentration-time curve (AUC) remained unchanged, compared to a single oral dose administration (1300 mg). Plasma concentrations reached steady state at the 5th dose of tranexamic acid tablets on Day 2.

The mean plasma pharmacokinetic parameters of tranexamic acid determined in 19 healthy women following a single (1300 mg) and multiple (1300 mg tablets three times daily for 5 days) oral dose of tranexamic acid tablets are shown in Table 3.

Effect of food : Tranexamic acid tablets may be administered with or without food. A single dose administration (1300 mg) of tranexamic acid tablets with food increased both C maxand AUC by 7% and 16%, respectively.

Distribution — Tranexamic acid is 3% bound to plasma proteins with no apparent binding to albumin. Tranexamic acid is distributed with an initial volume of distribution of 0.18 L/kg and steady-state apparent volume of distribution of 0.39 L/kg.

Tranexamic acid crosses the placenta. The concentration in cord blood after an intravenous injection of 10 mg/kg to pregnant women is about 30 mg/L, as high as in the maternal blood.

Tranexamic acid concentration in cerebrospinal fluid is about one tenth of the plasma concentration.

The drug passes into the aqueous humor of the eye achieving a concentration of approximately one tenth of plasma concentrations.

Elimination — Most elimination post intravenous administration occurred during the first 10 hours, giving an apparent elimination half-life of approximately 2 hours. The mean terminal half-life of tranexamic acid is approximately 11 hours. Plasma clearance of tranexamic acid is 110-116 mL/min.

Metabolism — A small fraction of the tranexamic acid is metabolized.

Excretion — Tranexamic acid is eliminated by urinary excretion primarily via glomerular filtration with more than 95% of the dose excreted unchanged. Excretion of tranexamic acid is about 90% at 24 hours after intravenous administration of 10 mg/kg.

Pediatric Patients — Tranexamic acid tablets are indicated for females of reproductive age (not approved for use in premenarcheal girls). In a randomized, single dose, two-way crossover study of two dose levels (650 mg and 1,300 mg), pharmacokinetics of tranexamic acid was evaluated in 20 female adolescents (12 to 16 years of age) with heavy menstrual bleeding. The C maxand AUC values after a single oral dose of 650 mg in the adolescent females were 32 – 36% less than those after a single oral dose of 1,300 mg in the adolescent females. The C maxand AUC values after a single oral dose of 1300 mg in the adolescent females were 20 – 25% less than those in the adult females given the same dose in a separate study. [See Use in Specific Populations (8.4)]

Patients with Renal Impairment — The effect of renal impairment on the disposition of tranexamic acid tablets has not been evaluated. Urinary excretion following a single intravenous injection of tranexamic acid declines as renal function decreases. Following a single 10 mg/kg intravenous injection of tranexamic acid in 28 patients, the 24-hour urinary fractions of tranexamic acid with serum creatinine concentrations 1.4 – 2.8, 2.8 – 5.7, and greater than 5.7 mg/dL were 51, 39, and 19%, respectively. The 24-hour tranexamic acid plasma concentrations for these patients demonstrated a direct relationship to the degree of renal impairment. Therefore, a lower dosage is needed in patients with renal impairment [see Dosage and Administration (2.2) ].