MESALAZINE-ASSOCIATED INTERSTITIAL NEPHRITIS

Background. When used for oral treatment of inflammatory bowel disease , Asacol (a coated form of mesalazine = 5-aminosalicylic acid) can cau se interstitial nephritis. The spectrum of severity, frequency of occu rrence and the best renal function test to detect this complication ar e not known. The value of immunosuppression in addition to drug withdr awal is similarly undetermined. Methods. Four cases of interstitial ne phritis which occurred in association with oral Asacol treatment are p resented and a further 12 cases who received similar treatment are rev iewed. Clinical trials published previously were scrutinized to assess the frequency of impaired renal function. Results. The available evid ence suggests that renal impairment of any severity may occur in up to 1 in 100 patients, but that clinically significant interstitial nephr itis occurs in less than 1 in 500 patients. This is most reliably dete cted by an elevated serum creatinine concentration. If the diagnosis o f nephrotoxicity is delayed until 18 months after commencement of medi cation, restoration of renal function, which is seen on withdrawal of medication alone up to 10 months, does not occur and there is no evide nce to date to indicate that addition of immunosuppression confers any significant advantage at this later stage. Conclusions. It is suggest ed that serum creatinine concentration should be measured each month f or the first 3 months of treatment, 3-monthly for the remainder of the first year and annually thereafter. The use of concurrent immunosuppr essive therapy may necessitate extension to the period of intensive mo nitoring. Any elevation of serum creatinine which cannot be related to a relapse of inflammatory bowel disease should prompt immediate withd rawal of Asacol and related medications and substitution of alternativ e therapy. Neither the lack of urinary abnormalities on routine testin g nor the absence of clinical or laboratory features of drug allergy c an be relied upon to rule out interstitial nephritis during oral thera py with these drugs.