Effect of plasma exchange on antifactor Xa activity of enoxaparin and serum levetiracetam levels.

PURPOSE: The effect of therapeutic plasma exchange (TPE) on antifactor Xa activity in a patient treated with enoxaparin and levetiracetam is reported.

SUMMARY: A 52-year-old woman was treated with levetiracetam and prophylactic enoxaparin while receiving TPE to manage respiratory failure due to anti-MDA5 antibody-associated interstitial lung disease (ILD) with dermatomyositis. Due to a scant amount of evidence regarding the management of these medications in TPE, therapeutic monitoring principles were used to assess the effect TPE had on these medications. A pre-TPE antifactor Xa activity level and levetiracetam serum assay, a post-TPE antifactor Xa activity level and levetiracetam serum assay, levetiracetam serum assays at 1 and 6 hours after the patient received her next dose, and a levetiracetam assay of the waste plasma from the TPE were collected for therapeutic drug monitoring and pharmacokinetic calculations. Utilizing standard population pharmacokinetic data, the expected antifactor Xa activity without TPE was 0.14 IU/mL. This concentration was significantly higher than the undetectable concentration (<0.1 IU/mL) that was drawn immediately after TPE, suggesting significant removal of antifactor Xa activity. The measured levetiracetam level did not significantly differ from the expected post-TPE levetiracetam level that was calculated using patient-specific pharmacokinetic data.

CONCLUSION: In a patient receiving TPE to manage anti-MDA5 antibody ILD associated with dermatomyositis and a prior seizure, TPE significantly altered enoxaparin antifactor Xa activity as evidenced by the undetectable antifactor Xa activity level drawn after TPE. Alternatively, TPE had a minimal effect on the clearance of levetiracetam as evidenced by the post-TPE level and fraction elimination of only 5% of total body stores.