Leflunomide

TEST: 070021
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CPT: 80299
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Synonyms

  • A77/1726
  • Arava®
  • Teriflunomide

Expected Turnaround Time

4 - 9 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Related Documents

Specimen Requirements

Specimen

Serum

Volume

1 mL

Minimum Volume

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

Container

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.

Collection

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

Freeze

Stability Requirements

Temperature

Period

Room temperature

Unstable

Refrigerated

Unstable

Frozen

6 months

Causes for Rejection

Serum separator tube; nonfrozen sample; gel-barrier tubes

Test Details

Use

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).

Limitations

This test was developed and its performance characteristics determined by LabCorp. It has not been cleared or approved by the Food and Drug Administration.

Methodology

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

References

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.

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