DRUG INTERACTIONS
Coadministration of Drugs that Affect Hemostasis
Since there is an increased risk of bleeding with Xigris, caution should be employed when Xigris is used with other drugs that affect hemostasis [see Warnings and Precautions and Clinical Pharmacology].
Coadministration of Prophylactic Heparin
Heparin for venous thromboembolism (VTE) prophylaxis may be coadministered with Xigris [see Warnings and Precautions and Clinical Studies]. No dosage adjustment of Xigris is recommended when coadministered with prophylactic heparin [see Clinical Pharmacology].
Interference with Coagulation Assays
Xigris has minimal effect on the prothrombin time (PT). Prolongation of the activated partial thromboplastin time (APTT) in patients with severe sepsis receiving Xigris may be due to the underlying coagulopathy, the pharmacodynamic effect of Xigris, and/or the pharmacodynamic effect of other concurrent medications. The effect of Xigris on the APTT assay is dependent on the reagent and instrument used to perform the assay and the time that elapses between sample acquisition and assay performance. Drotrecogin alfa (activated) present in a plasma sample will be gradually neutralized by endogenous inhibitors. Due to these biological and analytical variables, the APTT should not be used to assess the pharmacodynamic effect of Xigris. The interpretation of sequential determination of the PT and/or APTT should take these variables into consideration.
Because Xigris may affect the APTT assay, drotrecogin alfa (activated) present in plasma samples may interfere with one-stage coagulation assays based on the APTT (such as factor VIII, IX, and XI assays). This interference may result in a measured factor concentration that is lower than the actual concentration. Drotrecogin alfa (activated) present in plasma samples does not interfere with one-stage factor assays based on the PT (such as factor II, V, VII, and X assays).
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