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Apixaban

Test code(s) 94223

Question 1. What is apixaban?

Apixaban (Eliquis®) is an oral factor Xa inhibitor that inhibits thrombin generation, which is critical for clot formation. As an anticoagulant, it is indicated to: 1) reduce the risk of stroke and systemic embolism in patients with nonvalvular atrial fibrillation, 2) prevent deep venous thrombosis (DVT) in patients whom have undergone hip or knee replacement surgery, 3) treat DVT and pulmonary embolism (PE), and 4) reduce the risk of recurrent DVT and PE following initial therapy.1

Question 2. Is routine therapeutic monitoring of apixaban required?

No, apixaban has a highly predictable pharmacokinetic profile. Measurement of the drug’s level may be useful, however, when2:

  • There is a concern regarding patient compliance and adherence.
  • A patient has a very high or low body weight.
  • A patient is pregnant.
  • There is concurrent administration of a strong inducer of P-glycoprotein and CYP3A4 (eg, phenytoin, carbamazepine, phenobarbital, or St. John’s wort).
  • There is concurrent administration of a strong inhibitor of P-glycoprotein and CYP3A4 (eg, azole antimycotics, including ketoconazole, itraconazole, voriconazole, and posaconazole).
  • There is concurrent administration of an HIV protease inhibitor (eg, ritonavir).
  • There is a thrombotic or hemorrhagic event during therapy.
  • A patient has renal or hepatic failure.
  • A patient on apixaban therapy is scheduled for surgery.
  • A patient is elderly.
  • A patient has active cancer.

Question 3. What are the therapeutic ranges for the apixaban assay?

Because apixaban is administered in fixed doses and does not require routine laboratory monitoring, there are no universally established therapeutic ranges. The steady-state peak and trough ranges for various doses are shown below.

Question 4. Which method is used for apixaban measurement?

Apixaban is measured using a modified, chromogenic anti-Xa method. The optical density derived from the patient sample is compared to that of calibrators with known apixaban concentration. The results are reported in ng/mL.

Question 5. How sensitive is the apixaban assay?

The lower limit of detection for the apixaban assay is 30 ng/mL. Trough levels may be below this value; therefore, we suggest samples be collected at the peak (3-4 hours after the last dose).

Question 6. How specific is the apixaban assay?

The assay is not specific for apixaban. It will detect any anti-Xa anticoagulant including unfractionated heparin, low molecular weight heparins (enoxaparin, tinzaparin, dalteparin), rivaroxaban, and fondaparinux.

Question 7. How reproducible is the apixaban assay?

The coefficient of variation (CV) is less than 6%.

Question 8. Does anything interfere with apixaban measurements?

Gross lipemia, icterus, and hemolysis will interfere with apixaban measurement.

References

  1. Eliquis® (apixaban) [package insert]. Princeton, NJ: Bristol-Meyers Squibb Company; 2016.
  2. Cuker A, Siegal DM, Crowther MA, et al. Laboratory measurement of the anticoagulant activity of the non-vitamin K oral anticoagulants. J Am Coll Cardiol. 2014;64:1128-1139.
This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.
Document FAQS.189 Version: 0
Effective 01/16/2017 to present