METHOTREXATE AND PROBENECID
Probenecid markedly increases serum methotrexate levels (3- to 4-fold).
A marked increase in both the therapeutic and toxic effects of methotrexate can occur, apparently even with low doses if other risk factors are present (e.g. renal impairment, concurrent NSAIDs). Anticipate the need to reduce the dosage of the methotrexate and monitor the effects well if probenecid is also taken. If this is not possible, avoid the combination.
A marked increase in both the therapeutic and toxic effects of methotrexate can occur, apparently even with low doses if other risk factors are present (e.g. renal impairment, concurrent NSAIDs). Anticipate the need to reduce the dosage of the methotrexate and monitor the effects well if probenecid is also taken. If this is not possible, avoid the combination.