Systemic uptake of 5-aminosalicylic acid from olsalazine and eudragit L coated mesalazine in patients with ulcerative colitis in remission

Aminosalicylates are used to maintain remission in patients with ulcerative colitis. Since there are potential systemic side effects of 5-aminosalicylic acid (5-ASA) and long term treatment is necessary for maintenance therapy preparations with low rates of absorption in the small intestine would be optimal for this indication. In this trial olsalazine (Dipentum(R)), a 5-ASA dimer, and an eudragit L coated mesalazine preparation (Salofalk(R)) were compared. Patients and methods: Fifteen patients with ulcerative colitis in clinical and endoscopical remission were randomized in a cross over design. They either received 2 x 2 capsules of olsalazine 250 mg or 3 x 2 tablets mesalazine 250 mg, these being the doses recommended for maintenance therapy. After a five days equilibration period morning pre-dose serum samples and 24 hour urine were collected on two consecutive days and analyzed for 5-ASA and acetylated 5-ASA. Subsequently, patients were crossed over to receive the alternative preparation and were evaluated after five days correspondingly. Results: Uptake of 5-ASA from mesalazine was significantly higher than from olsalazine (p < 0.0001). Plasma concentrations of 5-ASA were 3.4 times and of acetyl-5-ASA 3.2 times higher after mesalazine administration than after olsalazine. The same applies to the 24 hour 5-ASA and acetyl-5-ASA urinary excretion (median: 3.2 versus 1.0 mmol/24 hr) as well as to the percentage of administered dose (32.4 versus 17.7%). All patients finished the trial and no major systemic side effects occured with either preparation. Conclusion: Systemic uptake of 5-ASA from olsalazine was significantly lower than from eudragit L coated mesalazine. Therefore, olsalazine is less likely to produce side effects and seems to be especially suited for maintenance therapy in ulcerative colitis.