Flanax/Flanax Forte Drug Interactions

Due to the high plasma protein-binding of naproxen, patients simultaneously receiving hydantoins should be closely monitored for adjustment of dose if required. Interactions have not been observed in clinical studies with Flanax/Flanax Forte and anticoagulants or sulfonylureas, but caution is advised, since interaction has been seen with other nonsteroidal agents of this class.
The natriuretic effect of furosemide has been reported to be inhibited by some drugs of this class. Inhibition of renal lithium clearance leading to an increase in plasma lithium concentration has been reported also.
Flanax/Flanax Forte and other NSAIDs can reduce the antihypertensive effect of propranolol and other β-blockers.
Probenecid given concurrently increases naproxen plasma levels and extends its plasma half-life significantly.
Concomitant administration of Flanax/Flanax Forte and methotrexate should be done with caution, because naproxen has been reported among other NSAIDs to reduce the tubular secretion of methotrexate in an animal model and thus, possibly enhance its toxicity.
It is suggested that Flanax/Flanax Forte therapy be temporarily discontinued 48 hrs before adrenal function tests are performed, because it may artificially interfere with some tests for 17-ketogenic steroids. Similarly, it may interfere with some urinary assays of 5-hydroxyindole acetic acid.