ARUP's Laboratory Test Directory

Leflunomide Metabolite, Serum or Plasma : 2007460
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Additional Technical Information
  


Mnemonic: LEFLUMETSP

Methodology: High Performance Liquid Chromatography/Mass Spectrometry
Performed: Tue, Fri
Reported: 1-6 days
Specimen Required: Patient Prep: Timing of specimen collection: Predose (trough). Obtain specimen 12 - 24 hours after last dose.

Collect: Plain red. Also acceptable: Lavender (EDTA), pink (K2EDTA), green (sodium heparin), or gray (sodium fluoride).

Specimen Preparation: Separate from cells within 2 hours of draw. Transfer 1 mL serum or plasma to an ARUP Standard Transport Tube. (Min: 0.2 mL)

Storage/Transport Temperature: Refrigerated. Also acceptable: Room temperature or frozen.

Unacceptable Conditions: Whole blood. Potassium oxalate or separator tubes.

Stability (collection to initiation of testing): Ambient: 7 days; Refrigerated: 17 days; Frozen: 90 days
Reference Interval:
Therapeutic Range Greater than 40.000 µg/mL
Toxic Level Not well established.

Interpretive Data: Therapeutic and toxic ranges are not well established. Concentrations greater than 40.000 µg/mL tend to correlate with improved patient outcome. A proposed therapeutic range is 50.000 - 100.000 µg/mL. Adverse reactions to Leflunomide, such as diarrhea, hypertension, and liver toxicity, do not correlate well with serum drug concentrations. Leflunomide has a potential risk for teratogenesis. For women being treated with Leflunomide who desire to become pregnant, enhanced drug elimination should be performed until plasma teriflunomide concentrations are lower than 0.020 µg/mL on two separate tests taken at least 14 days apart.

See Compliance Statement B: www.aruplab.com/CS
CPT Code(s): 80299
Cross References: Arava® (Leflunomide (Teriflunomide), Serum or Plasma)