Structure-function relationships of factor Xa inhibitors: implications for the practicing clinician

Probable rivaroxaban-induced erythema multiforme in children: A case report

Background: Limited data exists on the use of rivaroxaban for the treatment of pediatric patients. This report presents a case of probable rivaroxaban-induced Erythema Multiforme in Children. Case Summary: A female patient aged 5.5 years with antiphospholipid syndrome (APS) was administered oral rivaroxaban tablets 2.5 mg twice a day for 16 days. Subsequently, the patient developed a slight itching sensation on both feet and buttocks without an apparent cause. The following day, erythema multiforme appeared across the body in a scattered pattern. The erythema presented higher than the skin surface and partially merged into areas of the skin. Following an increase in the extent and degree of the erythema, all oral medications were ceased. Treatment with dexamethasone sodium phosphate injection, mometasone furoate cream, and mucopolysaccharide polysulfate cream resulted in an improvement of erythema multiforme. The erythema diminished and did not deteriorate subsequent to changing from rivaroxaban tablets to warfarin sodium tablets, and receiving nadroparin calcium injection.

In Vitro Antithrombotic, Hematological Toxicity, and Inhibitor Studies of Protocatechuic, Isovanillic, and p-Hydroxybenzoic Acids from Maclura Tricuspidata (Carr.) Bur

In blood coagulation, circulating platelets and coagulation factors are crucial for the primary process because thrombi are generated by fibrin clotting with fibrinogen, thrombin, FXIIIa, and platelet activation. Therefore, strategies to reduce the activity of key coagulation factors, or interfere with their functions and delay the activation of platelets can be used as important tools to suppress excessive blood clot formation and platelet hyperactivation. This study examined the antithrombotic activity and hematological toxicity of PA, IVA, and 4-HA isolated from M. tricuspidata (Carr.) Bur in several in vitro experiments and inhibitor assays. We found that PA, IVA, and 4-HA attenuated the formation of fibrin polymers/clots and degraded the blood clots. These compounds inhibited the activities of procoagulant proteases and fibrinoligase, and prolonged the coagulation time. There was a significant reduction in platelet function and ATP or serotonin levels in thrombin-activated platelets. An inhibitor study showed that PA exhibited a mixed inhibition type for thrombin, an uncompetitive inhibition type for FXa, and a non-competitive inhibition type for FXIIIa and IVA, while 4-HA exhibited an uncompetitive inhibition type for thrombin and non-competitive inhibition type for FXa and FXIIIa. These three compounds (up to 50 μg/mL) were not toxic to blood cells.

Factor Xa inhibitors: critical considerations for clinical development and testing

The selection of factor (F) X and its activated protease FXa for targeted inhibition to prevent and treat thrombotic conditions is based on an understanding of coagulation biochemistry, sequential steps that occur on tissue factor bearing cells and the interface of coagulation proteins, platelets, mononuclear cells and the nuclear constituents of inflammatory cells. The goal for developing direct oral FXa inhibitors was to achieve rapid, selective, predictable, safe and effective anticoagulation across a broad group of patients expected to derive benefit. The history and development in patient care are exemplars of knowledge, translation and collaboration between the public and private sectors.

Direct-Acting Oral Anticoagulants and Their Reversal Agents-An Update

Background: Over the last ten years, a new class of drugs, known as the direct-acting oral anticoagulants (DOACs), have emerged at the forefront of anticoagulation therapy. Like the older generation anticoagulants, DOACs require specific reversal agents in cases of life-threatening bleeding or the need for high-risk surgery. Methods: Published literature was searched, and information extracted to provide an update on DOACS and their reversal agents. Results: The DOACs include the direct thrombin inhibitor—dabigatran, and the factor Xa inhibitors—rivaroxaban, apixaban, edoxaban, and betrixaban. These DOACs all have a rapid onset of action and each has a predictable therapeutic response requiring no monitoring, unlike the older anticoagulants, such as warfarin. Two reversal agents have been approved within the last five years: idarucizumab for the reversal of dabigatran, and andexanet alfa for the reversal of rivaroxaban and apixaban. Additionally, ciraparantag, a potential “universal” reversal agent, is currently under clinical development. Conclusions: A new generation of anticoagulants, the DOACs, and their reversal agents, are gaining prominence in clinical practice, having demonstrated superior efficacy and safety profiles. They are poised to replace traditional anticoagulants including warfarin.

Mechanistic Basis for the Differential Effects of Rivaroxaban and Apixaban on Global Tests of Coagulation

Rivaroxaban and apixaban are both small molecules that reversibly inhibit factor Xa. Compared with rivaroxaban, apixaban has minimal effects on the prothrombin time and activated partial thromboplastin time. To investigate this phenomenon, we used a factor Xa-directed substrate in a buffer system. Although rivaroxaban and apixaban inhibited factor Xa with similar K _i values at equilibrium, kinetic measurements revealed that rivaroxaban inhibited factor Xa up to 4-fold faster than apixaban ( p  < 0.001). Using a discontinuous chromogenic assay to monitor thrombin production by prothrombinase in a purified system, rivaroxaban was 4-fold more potent than apixaban (K _i values of 0.7 ± 0.3 and 2.9 ± 0.5 nM, respectively; p  = 0.02). Likewise, in thrombin generation assays in plasma, rivaroxaban prolonged the lag time and suppressed endogenous thrombin potential to a greater extent than apixaban. To characterize how the two inhibitors differ in recognizing factor Xa, inhibition of prothrombinase was monitored in real-time using a fluorescent probe for thrombin. The data were fit using a mixed-inhibition model and the individual association and dissociation rate constants were determined. The association rates for the binding of rivaroxaban to either free factor Xa or factor Xa incorporated into the prothrombinase complex were 10- and 1,193-fold faster than those for apixaban, respectively, whereas dissociation rates were about 3-fold faster. Collectively, these findings suggest that rivaroxaban and apixaban differ in their capacity to inhibit factor Xa and provide a plausible explanation for the observation that rivaroxaban has a greater effect on global tests of coagulation than apixaban.

Probable Rivaroxaban-Induced Full Body Rash: A Case Report

INTRODUCTION

Rivaroxaban is a novel oral anticoagulant with several indications, one of which is for stroke prevention in nonvalvular atrial fibrillation. We present a case of probable rivaroxaban-induced rash.

CASE SUMMARY

A 79-year-old female with a medical history of atrial fibrillation experienced a stroke, after which she was prescribed rivaroxaban 20 mg. After several days, she developed a rash requiring admission to the emergency department and several days of treatment. The rash resolved and she was switched from rivaroxaban to apixaban and did not experience any adverse drug events.

DISCUSSION

Onset of symptoms occurred within days of rivaroxaban initiation. The patient had no allergy history and never reported a similar reaction while on concurrent home medication regimen. The resolution of rash and toleration of apixaban suggest a rivaroxaban-specific reaction. The mechanism of this rash is currently unclear.

CONCLUSION

We report one of the first cases of probable rivaroxaban-induced rash, whereas the patient tolerated apixaban. Further investigation is warranted, but prescribers should be cognizant of this potential issue when choosing a factor Xa inhibitor for anticoagulation.