Pharmacokinetic evaluation of rivaroxaban for the treatment of acute coronary syndromes

Rivaroxaban population pharmacokinetic and pharmacodynamic modeling in Iranian patients

WHAT IS KNOWN AND OBJECTIVE

Although predictable pharmacokinetic and pharmacodynamic of rivaroxaban allow fixed dosing regimens without routine coagulation monitoring, there is still the necessity to monitor and predict the effects of rivaroxaban in specific conditions and different populations. The current study was designed and conducted to analyze the rivaroxaban population pharmacokinetics in Iranian patients and establish a pharmacokinetic/pharmacodynamic model to predict the relationship between rivaroxaban concentration and its anticoagulant activity.

METHODS

A sequential nonlinear mixed effect pharmacokinetic/pharmacodynamic modeling method was used to establish the relation between rivaroxaban concentration and anti-factor Xa activity, prothrombin time, and activated partial thromboplastin time (aPTT) as pharmacodynamic biomarkers in a population of sixty-nine Iranian patients under treatment with oral rivaroxaban. Rivaroxaban plasma concentration was quantified by a validated high-performance liquid chromatography-tandem mass spectrometry.

RESULTS AND DISCUSSION

The typical population values (inter-individual variability%) of the oral volume of distribution and clearance for a one-compartment model were 61.2 L (21%) and 3.68 L·h^-1 (61%), respectively. Creatinine clearance and Child-Turcotte-Pugh score were found to affect the clearance. A direct link linear structural model best fitted the data for both prothrombin time and aPTT. The baseline estimates of aPTT and prothrombin time in the population were 35.0 (15%) and 12.6 (2%) seconds, respectively. The slope of the relationship between apTT, prothrombin time, and rivaroxaban concentration was 0.033 (28%) and 0.018 (54%) s·ml·ng^-1 , respectively. The selected model for anti-factor Xa activity consisted of a direct link inhibitory E_max model with Hill coefficient. The maximum level of inhibition (E_max ) was 4 IU·ml^-1 . The concentration of rivaroxaban producing 50% of the maximum inhibitory effect (EC₅₀ ) was 180 (24%) ng·ml^-1 , and Hill coefficient (γ) was 1.44 (108%). No covariates showed a statistically significant effect on PT and activated partial thromboplastin time prolonging properties and anti-factor Xa activity.

WHAT IS NEW AND CONCLUSION

Our results confirmed that pharmacokinetic/pharmacodynamic models similar to those of the other studies describe the relationship between the rivaroxaban concentration and its anticoagulant effect in Iranian patients. However, considerable differences were observed in the parameters of the pharmacodynamics-pharmacokinetic models with the results of other reports that can explain the unpredictable effects of rivaroxaban in some patients.

Naringenin has an inhibitory effect on rivaroxaban in rats both in vitro and in vivo

Food–drug interactions are reported to have some impacts on the pharmacokinetics and pharmacodynamics of various oral drugs. To better understand the effects of naringenin, one natural product in many fruits, on the pharmacokinetics of rivaroxaban, drug–drug interactions (DDIs) between naringenin and rivaroxaban in vitro were investigated in Sprague–Dawley (SD) rat liver microsomes. For the DDIs in vivo, 12 male SD rats were randomly divided into the experimental group and the control group with six rats in each group. Rats in the experimental group were pre‐treated with naringenin (10 mg/kg/day) for 2 weeks before the administration of rivaroxaban (10 mg/kg) by oral gavage, while the rats in the control group were given rivaroxaban (10 mg/kg) only once. The plasma concentration of rivaroxaban in rats was then measured by UPLC‐MS/MS. In vitro data indicated that naringenin could decrease the metabolic clearance rate of rivaroxaban with the IC₅₀ value of 38.89 μM, and exhibited a mixed inhibition to rivaroxaban (Ki =54.91 μM, aKi =73.33 μM, a = 0.74). In vivo data in rats revealed that as compared with that of the control group, the AUC_(0–t) value of rats in the experimental group was increased from 2406.28 ± 519.69 μg/h/L to 4005.04 ± 1172.76 μg/h/L, the C_max value was increased from 310.23 ± 85.76 μg/L to 508.71 ± 152.48 μg/L, and the V_z/F and CL_z/F were decreased from 23.03 ± 4.81 L/kg to 16.2 ± 8.42 L/kg, 4.26 ± 0.91 L/h/kg to 2.57 ± 0.73 L/h/kg, respectively. These data indicated that naringenin had an inhibitory effect on the pharmacokinetics of rivaroxaban in rats, suggesting that the DDIs between naringenin and rivaroxaban might occur when they were co‐administered in the clinic.

Rivaroxaban: a review of its use in acute coronary syndromes

Rivaroxaban (Xarelto(®)) is an orally administered highly selective direct inhibitor of factor Xa that has been approved in many countries to reduce the risk of stroke in patients with atrial fibrillation and for the treatment and prevention of venous thromboembolism. More recently, rivaroxaban at a low dosage of 2.5 mg twice daily, co-administered with aspirin alone or aspirin plus either clopidogrel or ticlopidine, was approved for use in the EU for patients with a recent acute coronary syndrome (ACS). The approval of rivaroxaban in ACS was primarily based on findings of the phase III ATLAS ACS 2-TIMI 51 trial, which showed that after a median of 13.1 months of treatment with rivaroxaban 2.5 mg twice daily (combined with aspirin or aspirin plus either clopidogrel or ticlopidine) there was a statistically significant reduction in the rate of the primary composite endpoint, which was death from cardiovascular causes, myocardial infarction or stroke, compared with placebo. Rivaroxaban 2.5 mg twice daily was also associated with a reduction in all-cause and cardiovascular mortality. There was an increase in the risk of major bleeding and intracranial haemorrhage with rivaroxaban 2.5 mg twice daily compared with placebo; however, there was no increase in the risk of fatal bleeding. Aspirin plus either ticagrelor or prasugrel was not evaluated as background dual antiplatelet therapy in ATLAS ACS 2-TIMI 51 and the safety implications of rivaroxaban used in combination with such therapy are unknown. In conclusion, results of the ATLAS ACS 2-TIMI 51 trial suggest a potentially important role for rivaroxaban 2.5 mg twice daily co-administered with aspirin alone or aspirin plus either clopidogrel or ticlopidine in patients with a recent ACS.

Role of oral factor Xa inhibitors after acute coronary syndrome

Despite an early invasive strategy and the use of dual antiplatelet therapy, patients with acute coronary syndrome (ACS) continue to be at substantial risk for recurrent ischemic events. It is believed that this risk is, at least in part, due to an intrinsic coagulation pathway that remains activated for a prolonged period after ACS. Earlier studies using warfarin showed a reduction in ischemic events, but the overall benefits were offset by increased bleeding complications. Recently, there has been increased interest in the potential role of new oral anticoagulants, some of which target factor Xa, after ACS. Factor Xa is important for the coagulation pathway and also plays a role in cellular proliferation and inflammation. It may thus be an attractive target for therapeutic intervention in ACS. Recently, various oral factor Xa inhibitors have been studied as potential treatment options for ACS. This review will focus on currently available data to evaluate the possible role of factor Xa inhibitors in the management of patients with ACS.