Mesalamines are slow-release formulations of 5-aminosalicylic acid (5-ASA) and 
are effective as primary treatment and maintenance therapy in inflammatory bowel 
disease. Interstitial nephritis is a recognized side effect. We report two cases 
of biopsy-confirmed interstitial nephritis in patients being treated with 5-ASA. 
Both had a trial of steroid therapy. One patient had partial recovery of renal 
function but the other patient was in chronic renal failure and likely was 
approaching the need for dialysis. Interstitial nephritis is an under-recognized 
complication of 5-ASA therapy. Early identification and withdrawal of this drug 
can lead to a partial or complete reversal of renal dysfunction.