Pharmacokinetics, safety, and efficacy of combination treatment with methotrexate and leflunomide in patients with active rheumatoid arthritis.
OBJECTIVE
To examine the safety and pharmacokinetics of and clinical response to leflunomide, a de novo pyrimidine synthesis inhibitor, when administered to patients with active rheumatoid arthritis (RA) who have been receiving long-term methotrexate therapy.


METHODS
This was an open-label, 52-week study in which 30 patients with RA that remained active despite therapy with methotrexate at 17+/-4 mg/week (mean +/- SD) for > or =6 months were given leflunomide, 10-20 mg/day. Patients were assessed for adverse effects, pharmacokinetic measurements of leflunomide and methotrexate, and clinical response by American College of Rheumatology (ACR) 20% response criteria.


RESULTS
Twenty-three patients completed 1 year of treatment. No significant pharmacokinetic interactions between leflunomide and methotrexate were noted. This combination therapy was generally well tolerated clinically, with the exception of elevations of liver enzyme levels. Seven patients withdrew from the treatment regimen: 2 withdrawals were voluntary, 3 were due to persistent elevation of plasma transaminase levels, and 2 were due to lack of efficacy. Of the patients, 16 (53%) met ACR 20% response criteria. Two met ACR criteria for remission after 1 year.


CONCLUSIONS
The combination of methotrexate and leflunomide has therapeutic potential in RA.
Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
M E
ME
Weinblatt
J M
JM
Kremer
J S
JS
Coblyn
A L
AL
Maier
S M
SM
Helfgott
M
M
Morrell
V M
VM
Byrne
M V
MV
Kaymakcian
V
V
Strand
D000328:Adult; D000410:Alanine Transaminase / Q000097:blood; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000188:drug therapy*; D001219:Aspartate Aminotransferases / Q000097:blood; D003967:Diarrhea / Q000139:chemically induced; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D007555:Isoxazoles / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D000077339:Leflunomide; D008099:Liver / Q000201:enzymology; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008875:Middle Aged; D009325:Nausea / Q000139:chemically induced; D010349:Patient Compliance; D016896:Treatment Outcome
D000894:Anti-Inflammatory Agents, Non-Steroidal; D007555:Isoxazoles; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D000077339:Leflunomide; D008727:Methotrexate