| Item |
Information |
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Drug Groups
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approved; investigational |
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Description
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Leflunomide is a pyrimidine synthesis inhibitor belonging to the DMARD (disease-modifying antirheumatic drug) class of drugs, which are chemically and pharmacologically very heterogeneous. Leflunomide was approved by FDA and in many other countries (e.g., Canada, Europe) in 1999. |
| Indication |
For the management of the signs and symptoms of active rheumatoid arthritis (RA) to improve physical function and to slow the progression of structural damage associated with the disease. Has also been used for the prevention of acute and chronic rejection in recipients of solid organ trasnplants and is designated by the FDA as an orphan drug for this use. |
| Pharmacology |
Leflunomide is a pyrimidine synthesis inhibitor indicated in adults for the treatment of active rheumatoid arthritis (RA). RA is an auto-immune disease characterized by high T-cell activity. T cells have two pathways to synthesize pyrimidines: the salvage pathways and the de novo synthesis. At rest, T lymphocytes meet their metabolic requirements by the salvage pathway. Activated lymphocytes need to expand their pyrimidine pool 7- to 8-fold, while the purine pool is expanded only 2- to 3-fold. To meet the need for more pyrimidines, activated T cells use the de novo pathway for pyrimidine synthesis. Therefore, activated T cells, which are dependent on de novo pyrimidine synthesis, will be more affected by leflunomide's inhibition of dihydroorotate dehydrogenase than other cell types that use the salvage pathway of pyrimidine synthesis. |
| Toxicity |
LD50=100-250 mg/kg (acute oral toxicity) |
| Affected Organisms |
| • |
Humans and other mammals |
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| Biotransformation |
Primarily hepatic. Leflunomide is converted to its active form following oral intake. |
| Absorption |
Well absorbed, peak plasma concentrations appear 6-12 hours after dosing |
| Half Life |
2 weeks |
| Protein Binding |
>99.3% |
| Elimination |
The active metabolite is eliminated by further metabolism and subsequent renal excretion as well as by direct biliary excretion. In a 28 day study of drug elimination (n=3) using a single dose of radiolabeled compound, approximately 43% of the total radioactivity was eliminated in the urine and 48% was eliminated in the feces. It is not known whether leflunomide is excreted in human milk.
Many drugs are excreted in human milk, and there is a potential for serious adverse reactions in nursing infants from leflunomide. |
| Distribution |
* 0.13 L/kg |
| References |
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Goldenberg MM: Leflunomide, a novel immunomodulator for the treatment of active rheumatoid arthritis. Clin Ther. 1999 Nov;21(11):1837-52; discussion 1821.
[Pubmed]
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Li EK, Tam LS, Tomlinson B: Leflunomide in the treatment of rheumatoid arthritis. Clin Ther. 2004 Apr;26(4):447-59.
[Pubmed]
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Sanders S, Harisdangkul V: Leflunomide for the treatment of rheumatoid arthritis and autoimmunity. Am J Med Sci. 2002 Apr;323(4):190-3.
[Pubmed]
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Breedveld FC, Dayer JM: Leflunomide: mode of action in the treatment of rheumatoid arthritis. Ann Rheum Dis. 2000 Nov;59(11):841-9. \
[Pubmed]
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Reitzik M, Lownie JF: Familial polyostotic fibrous dysplasia. Oral Surg Oral Med Oral Pathol. 1975 Dec;40(6):769-74.
[Pubmed]
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Herrmann ML, Schleyerbach R, Kirschbaum BJ: Leflunomide: an immunomodulatory drug for the treatment of rheumatoid arthritis and other autoimmune diseases. Immunopharmacology. 2000 May;47(2-3):273-89.
[Pubmed]
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Schattenkirchner M: The use of leflunomide in the treatment of rheumatoid arthritis: an experimental and clinical review. Immunopharmacology. 2000 May;47(2-3):291-8.
[Pubmed]
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Fox RI: Mechanism of action of leflunomide in rheumatoid arthritis. J Rheumatol Suppl. 1998 Jul;53:20-6.
[Pubmed]
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