Bioavailability of orally administered mesna

The bioavailability of orally administered sodium 2-mercaptoethane sulfonate (mesna, Uromitexan drink ampoules) was tested in 18 healthy probands and in 5 tumor patients. Following single oral administration of 20 or 40 mg/kg mesna, 52.4% and 52.6%, respectively, of the dose were excreted in the urine as reactive thiol groups, the remainder as mesna disulfide (dimesna), the only metabolite of mesna; after i.v. injection of 20 mg/kg mesna, 48.7% of the dose administered appeared as thiol groups in the urine. Not until after 13.1 h (20 mg/kg p.o.) and 18.5 h (40 mg/kg p.o.), respectively, concentration drops below the minimum concentration of 100 micrograms/ml presumed to be still reliably protective. However, the elimination pattern and the time when the threshold concentration is reached are subject to marked individual variation. After i.v. administration of 20 mg/kg mesna and 9 times oral administration of 20 mg/kg mesna (the first dose concurrently with the i.v. injection, thereafter every 4 h), or 7 times oral administration of 20 mg/kg mesna (the first dose again concurrently with the i.v. injection, thereafter every 5 h), the percentage of the total dose administered appearing as thiol groups in the urine averaged 41.9% and 37.6%, respectively, up to 17 or 18 h after the last dose. Comparison of periods covering the same time of the day showed the total amount excreted to be higher on day 2 than on day 1.(ABSTRACT TRUNCATED AT 250 WORDS)