CPT: 80375
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Test Details


  • A77/1726
  • Arava®
  • Teriflunomide


Leflunomide (Arava®) is a pyrimidine synthesis inhibitor used in the treatment of active rheumatoid arthritis. The drug is available in oral doses containing 10, 20, or 100 mg of active drug. Arava® is an isoxazole immunodulatory agent which inhibits dihydroorotate dehydrogenase (an enzyme involved in de novo pyrimidine synthesis) and has antiproliferative activity. Following oral administration, leflunomide is metabolized to an active metabolite, A77-1726 (teriflunomide), which is responsible for essentially all of its activity in vivo. Peak levels of this metabolite occurred 6 to 12 hours after dosing, with a long half-life (about two weeks).


Liquid chromatography/tandem mass spectrometry (LC/MS-MS)

Specimen Requirements




1 mL

Minimum Volume

0.5 mL (Note: This volume does not allow for repeat testing.)


Red-top tube. Do not use a gel-barrier tube. The use of gel-barrier tubes is not recommended due to slow absorption of the drug by the gel. Depending on the specimen volume and storage time, the decrease in drug level due to absorption may be clinically significant.


Serum must be separated from cells within 45 minutes of collection and transferred to a plastic transport tube. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions


Stability Requirements



Room temperature





6 months

Causes for Rejection

Serum separator tube; nonfrozen sample; gel-barrier tubes

Clinical Information


Brent RL. Teratogen update: Reproductive risks of leflunomide (Arava); a pyrimidine synthesis inhibitor: Counseling women taking leflunomide before or during pregnancy and men taking leflunomide who are contemplating fathering a child. Teratology. 2001 Feb; 63(2):106-112. 11241434
Physicians' Desk Reference. 66th ed. Montvale, NJ: Thompson PDR; 2012.


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
070021 Leflunomide Metabolite (ARAVA) 38901-5 070022 Leflunomide Metabolite (ARAVA) ng/mL 38901-5

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