Following single-dose administration of 2.25 g balsalazide (three 750 mg capsules) under fasting conditions in healthy subjects, mean urinary recovery of balsalazide, 5-ASA, and N-Ac-5-ASA was 0.2%, 0.22% and 10.2%, respectively.
In a multiple-dose study in healthy subjects receiving a balsalazide dose of two 750 mg capsules twice daily (3 g/day) for 10 days, mean urinary recovery of balsalazide, 5-ASA, and N-Ac-5-ASA was 0.1%, 0%, and 11.3%, respectively. During this study, subjects received their morning dose 0.5 hours after being fed a standard meal, and subjects received their evening dose 2 hours after being fed a standard meal.
In a study with 10 healthy volunteers, 65% of a single 2.25 g dose of balsalazide was recovered as 5-ASA, 4-aminobenzoyl-ß-alanine, and the N-acetylated metabolites in feces, while <1% of the dose was recovered as parent compound.
In a study that examined the disposition of balsalazide in patients who were taking 3 to 6 g of balsalazide daily for more than 1 year and who were in remission from ulcerative colitis, less than 1% of an oral dose was recovered as intact balsalazide in the urine. Less than 4% of the dose was recovered as 5-ASA, while virtually no 4-aminobenzoyl-ß-alanine was detected in urine. The mean urinary recovery of N-Ac-5-ASA and N-acetyl-4-aminobenzoyl-ß-alanine comprised <16% and <12% of the balsalazide dose, respectively. No fecal recovery studies were performed in this population.
All pharmacokinetic studies with balsalazide are characterized by large variability in the plasma concentration versus time profiles for balsalazide and its metabolites, thus half-life estimates of these analytes are indeterminate.