Apixaban (Eliquis) has been approved to prevent stroke and thrombus formation in patients with atrial fibrillation that isn't caused by a heart valve problem. The drug shouldn't be used if the patient has a prosthetic heart valve or has active pathologic bleeding. As a factor Xa inhibitor anticoagulant, apixaban decreases thrombin generation and thrombus development. It has no direct effect on platelet aggregation, although platelet aggregation is altered indirectly because apixaban decreases thrombin formation and thrombin is needed for platelets to clump. Apixaban lengthens the time it takes to clot, which is measured using the active partial thromboplastin time, prothrombin time, and international normalized ratio. However, changes in these values are small, highly variable, and not considered useful in monitoring the anticoagulant effect of apixaban. The drug's labeling doesn't offer any suggestions on how to use laboratory tests to monitor the effectiveness of the drug.
In clinical trials apixaban was found to be more effective than warfarin at decreasing the risk of hemorrhagic stroke and ischemic stroke with hemorrhagic conversion. The two drugs were similarly effective at reducing the risk of purely ischemic stroke. Apixaban was also found to be more effective at reducing the risk of systemic embolism than warfarin, while producing significantly fewer major bleeding episodes. When apixaban was compared with aspirin, it was found to be significantly superior in reducing the risk of stroke and systemic embolus, although there were more episodes of bleeding with apixaban than with aspirin. Sudden discontinuation of apixaban increases the risk of clots and stroke, although its anticoagulant effects will persist for 24 hours because of the drug's long half-life.
Like all anticoagulants, apixaban can produce bleeding, which may be severe. Coadministration of antiplatelet agents, fibrinolytics, heparin, or aspirin increases the risk of bleeding, as does chronic nonsteroidal antiinflammatory drug use. Caution must be used if these drugs are necessary.
Apixaban is a substrate of both the cytochrome P-450 (CYP) system's CYP3A4 isoenzyme and permeability glycoprotein (P-glycoprotein). When inhibitors of CYP3A4 and P-glycoprotein are given concurrently with apixaban, circulating levels of apixaban will rise, increasing the risk of bleeding. If inducers of CYP3A4 and P-glycoprotein are given concurrently with apixaban, circulating levels of apixaban will decrease, increasing the risk of stroke. There is no known antidote to overdosage from apixaban; it's therefore important to assess for potential drug interactions that would increase the risk of adverse effects. Nurses should use an electronic database to identify drugs that will produce these interactions with apixaban.
Patient education should include the signs of excessive bleeding with instructions to notify the prescriber immediately if they are noted. Patients should be instructed to take the drug twice daily. They should also be warned not to stop taking apixaban suddenly because that will increase their risk of stroke. For this reason it's important that they not allow their prescription to run out. If apixaban must be stopped suddenly, the nurse should consult the prescriber to ensure that adequate anticoagulant medication is prescribed.
For complete prescribing information, see http://1.usa.gov/WiQanY.