SYSTEMIC ABSORPTION OF 5-AMINOSALICYLIC ACID IN PATIENTS WITH INACTIVE ULCERATIVE-COLITIS TREATED WITH OLSALAZINE AND MESALAZINE

Objective: To compare the systemic load of 5-aminosalicylic acid (5-AS A) as a basis for potential long-term toxicity during treatment in usu al dosage with olsalazine (Dipentum) and one controlled-release mesala zine preparation (Salofalk) in patients with inactive ulcerative colit is. Design: Open, randomized, crossover study. Treatment schedule: Ols alazine 500 mg twice daily for 7 days and mesalazine 500 mg thrice dai ly for 7 days consecutively. Patients: Fifteen patients (12 males/3 fe males) aged between 18-70 years with ulcerative colitis in endoscopica lly confirmed remission for at least one month. Methods: A morning pre dose plasma sample and a 24-h urine collection on days 6 and 7 of each course were obtained from all patients for quantitative determination of 5-ASA and acetyl-5-ASA (Ac-5-ASA) concentrations. High performance liquid chromatography was used and all analyses were performed blindl y on coded samples. Results: Treatment with mesalazine compared with o lsalazine gave significantly higher levels of 5-ASA and Ac-5-ASA in pl asma and urine. Maximum values and ranges of all variables were higher in the mesalazine group than in the olsalazine group. It is noteworth y that there was clear discriminance in the range of urine 5-ASA and A c-5-ASA concentrations after mesalazine and olsalazine treatment. Conc lusion: 1. The mesalazine preparation used, in comparison with olsalaz ine given in usual dosages, causes significantly higher levels of 5-AS A and Ac-5-ASA in plasma and urine in patients with inactive ulcerativ e colitis. 2. The lower systemic load of 5-ASA may reduce the potentia l risk of adverse events and in particular of nephrotoxicity.