Although no pharmacokinetic interaction appears to occur between
methotrexate and
leflunomide elevated liver
enzyme levels have been seen.
The UK manufacturers say that concurrent use is not advisable. The US manufacturers say that if concurrent use is undertaken, monitoring should be increased to monthly intervals. Close liver
enzyme monitoring is also recommended if switching between these drugs, and colestyramine or activated charcoal washout should be performed when switching from
leflunomide to
methotrexate.