Probenecidside effects

Exacerbation of gout following therapy with probenecid may occur; in such cases colchicine or other appropriate therapy is advisable. Probenecid increases plasma concentrations of methotrexate in both animals and humans. In animal studies, increased methotrexate toxicity has been reported. If probenecid is given with methotrexate, the dosage of methotrexate should be reduced and serum levels may need to be monitored. In patients on probenecid the use of salicylates in either small or large doses is contraindicated because it antagonizes the uricosuric action of probenecid. The biphasic action of salicylates in the renal tubules accounts for the so-called “paradoxical effect” of uricosuric agents. In patients on probenecid who require a mild analgesic agent the use of acetaminophen rather than small doses of salicylates would be preferred. Rarely, severe allergic reactions and anaphylaxis have been reported with the use of probenecid. Most of these have been reported to occur within several hours after re-administration following prior usage of the drug. The appearance of hypersensitivity reactions requires cessation of therapy with probenecid.

Use in Pregnancy: Probenecid crosses the placenta barrier and appears in cord blood. The use of any drug in women of childbearing potential requires that the anticipated benefit be weighed against the possible hazards.

Hypersensitivity to probenecid. Children under 2 years of age. Not recommended in persons with known blood dyscrasias or uric acid kidney stones. Therapy with probenecid should not be started until an acute gouty attack has subsided.