Leflunomide as Metabolite Drug Level
Label Mnemonic: TERI
Epic Lab Code: LAB3489
Downtime Form: A-1a Miscellaneous Request
Commercial Mail-out Laboratory
5231 RCP
356-8593
Specimen(s):
Serum
Specimen Instructions:
Draw blood no sooner than 12 hours (trough value) after last dose.
Collection Medium:
Red top tube 5 mL (Clot Activator)
Minimum:
Preferred Minimum: 1.0 mL serum from red top tube
Rejection Criteria:
Gross Hemolysis and Lipemia.
Delivery Instructions:
Deliver to laboratory immediately after collection.
Turn Around Time:
2-5 days upon receipt at reference laboratory
Reference Range:
Therapeutic: >40 mcg/mL
Elimination: <0.020 mcg/mL
Interpretive Data:
Therapy: clinical targets for serum teriflunomide (leflunomide metabolite) concentrations are still being determined, but levels >40 mcg/mL appear to correlate with better outcome.

Elimination: serum concentrations <0.020 mcg/mL (20 ng/mL) are preferred to minimize potential teratogenesis for patients considering pregnancy.
Comments:
Useful For:
Therapeutic monitoring of patients actively taking leflunomide

Assessment of elimination in patients requiring enhanced elimination of the drug
Methodology:
High Turbulence Liquid Chromatography–Tandem Mass Spectrometry (HTLC- MS/MS)
CPT Code:
82542