Leflunomide Metabolite

Teriflunomide, Arava, Aubaigo

Test Codes

EPIC: LAB1231951, Beaker: LEFLUNOMIDE, Quest: 18865

Department

Send Outs

Specimen Collection Criteria

Collect (preferred specimen): One plain Red-top tube.
Also acceptable: One Sodium Heparin (green-top) or Lithium Heparin (green-top).

Not Acceptable: Serum separator tubes (SST) or Plasma separator tubes (PST).

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transfer serum to plastic transport tube and maintain at room temperature (20-26°C or 68-78.8°F) prior to transport.

Preparation for Courier Transport

Transport: 1.0 mL serum or plasma, room temperature (20-26°C or 68-78.8°F)). (Minimum: 0.5 mL)

Rejection Criteria

• Serum Separator (SST) tubes.
• Specimens not collected and processed as indicated.

In-Lab Processing

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transfer serum to plastic transport tube and maintain at room temperature (20-26°C or 68-78.8°F) prior to transport.

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 5 days
Refrigerated (2-8°C or 36-46°F): 14 days
Frozen (-20°C/-4°F or below): 30 days

Laboratory

Sent to Quest Diagnostics, Wood Dale, IL.

Performed

Tuesday, Thursday, Saturday.
Results available in 2-4 days.

Reference Range

Mean steady state plasma concentrations of teriflunomide from patients on daily dosages of 5, 10, or 25 mg of leflunomide were 8,800, 18,000 and 63,000 ng/mL, respectively. It is recommended that women of childbearing potential who discontinue leflunomide therapy undergo the cholestyramine drug elimination procedure. This procedure includes verification that plasma levels of teriflunomide are less than 20 ng/mL by two separate tests at least 14 days apart.

Test Methodology

Chromatography/Mass Spectrometry.

Clinical Utility

Leflunomide Metabolite - Leflunomide is an immunosuppressant medication used in the treatment of rheumatoid arthritis. Leflunomide is rapidly and extensively metabolized to teriflunomide, which is the active form of the medication. Steady state plasma concentrations in patients receiving recommended daily dosages: up to 63,000 ng/mL. It is recommended that all women of childbearing potential who discontinue leflunomide and women receiving treatment who wish to become pregnant undergo the cholestyramine drug elimination procedure. This procedure includes verification that plasma levels of teriflunomide are less than 20 ng/mL by two separate tests at least 14 days apart.

CPT Codes

80193
LOINC:  Teriflunomide 44828-2

Contacts

Last Updated

11/19/2025