Steady state disposition of 5-aminosalicyclic acid following oral dosing

In 18 healthy volunteers the steady state disposition of 5-aminosalicylic acid (5-ASA, mesalazine, CAS 89-57-6; 500 mg tid) was evaluated following the last oral dose in form of slow release tablets (Salofalk) either containing 500 mg or 250 mg 5-ASA. In none of the pharmacokinetic parameters of 5-ASA characterizing bioavailability (e.g. AUC approximately 6 ug/ml x h; Cmax approximately 1.7 micrograms/ml; tmax approximately 5 h; Cminss approximately 0.5 micrograms/ml; Cavss approximately 0.75 microgram/ml) differences between both forms were observed and the calculated 90% confidence intervals and point estimates indicated bioequivalence. Following the delayed absorption 5-ASA was rapidly eliminated (t1/2 = 1.4 +/- 0.5 h).