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Test ID: FARIX    
Arixtra (Fondaparinux) Level

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Units: mg/L


Test Performed by: BloodCenter of Wisconsin

                             638 N 18th Street

                             Milwaukee, WI 53233-2121

Interpretation Provides information to assist in interpretation of the test results

Interpretive comments:  Dosing protocols for Arixtra have been validated by empiric clinical trials. The relationship between pharmacokinetic parameters and efficacy or safety (bleeding) has not been reported, nor have guidelines for target fondaparinux levels been published in the medical literature. Drug elimination half-life is approximately 17-21 hours in normal individuals, but is prolonged in patients with renal insufficiency. "Mean observed" drug levels are available from patients enrolled in clinical trials. In patients receiving daily injections of 2.5 mg (for DVT prophylaxis),  the observed steady state mean peak level observed approximately 3 hours after injection was approximately 0.45 mg/L, with the

observed minimum mean steady state plasma level of approximately 0.17 mg/L before the next dose. In patients receiving 5-10 mg Arixtra (for treatment of DVT or pulmonary embolism), the observed mean steady state peak level averaged approximately 1.23 mg/L approximately 3 hours after injection, with the observed minimum mean steady state plasma concentration at 0.58 mg/L before the next dose.  (Data taken from prescribing information for Arixtra, and from GlaxoSmithKline informational materials.)