Chromogenic Substrate Assay
Used to monitor treatment with Arixtra (fondaparinux) when clinically indicated. Dosing protocols for DVT prophylaxis and treatment of DVT/PE have been validated by empiric clinical trials. Clinical monitoring with Arixtra levels is not necessary for most patients.
Normal individuals have no Arixtra activity.
Expected Therapeutic Ranges:
DVT prophylaxis (Arixtra 2.5mg qd)
3 hours after dose: 0.39-0.50mg/L
Trough: 0.14-0.19 mg/L drawn just prior to next dose.
Treatment of thrombosis (Arixtra 5-10mg qd)
3 hours after dose: 1.20-1.26 mg/L
Trough: 0.46-0.62 mg/L drawn just prior to next dose.
- Factor Xa Inhibition
- Anti-Xa Arixtra
- Chromogenic Xa
- Xa Chromogenic
- Anti-Xa Fondaparinux
- Coagulation Factor Xa Inhibition
- Arixtra Anti-Xa
- Factor 10a Inhibition
- Anti-10a Arixtra
STAT requests for this test will be performed on a STAT basis (supervisory staff approval is not required).
The sample should be drawn 3 hours after injection of drug in order to compare to published peak levels. Collect specimen in a blue top (citrate 3.2%) tube. Mix by inversion. Specimen should arrive at lab within 3 hours of collection; transport at room temperature. Alternatively, centrifuge, aliquot plasma into a plastic vial, and freeze the specimen within 4 hours of collection. Transport frozen specimen on dry ice. Collection of the blood through lines that have been previously flushed with heparin should be avoided. If the blood must be drawn through a VAD (vascular access device), the line should be flushed with 5 mL of saline and the first 5 mL of blood or six dead space volumes of the VAD discarded.