The Fate of [14C]Saccharin in Man, Rat and Rabbit and of 2-Sulphamoyl[14C]benzoic Acid in the Rat

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Abstract
1. [14C]Saccharin administered orally was excreted entirely unchanged by rats on a normal diet and by rats on a 1% and 5% saccharin diet for up to 12 months. Some 90% dose was excreted in 24 h, about 70–80% in urine and 10–20% in faeces. No metabolite was detected in the excreta by chromatography or reverse isotope dilution. No 14CO2 was found in the expired air and no 14CO32- or 2-sulphamoylbenzoic acid in the urine. 2. When [14C]saccharin was injected into bile-duct cannulated rats kept on a normal diet or on a 1% saccharin diet for 19 and 23 months, 0.1–0.3% dose appeared in the bile in 3 h and no more at 24 h after dosing. Most of the saccharin was excreted in the urine, 0.6% appearing in the faeces. 3. [14C]Saccharin given orally to rabbits kept on untreated water and on water containing 1% saccharin for 6 months was excreted unchanged, 60–80% in 24 h, with 70% in urine and 3–11% in faeces. 4. [3-14C]Saccharin taken orally was excreted unchanged mainly in urine (85–92% in 24 h) by 3 adult humans both before and after taking 1 g of saccharin daily for 21 days. No metabolite of saccharin was found. 5. When [14C]saccharin was administered orally to pregnant rats on the 21st day of gestation only at most 0.6% of dose entered the foetuses. The 14C cleared more slowly from the urinary bladder than from other maternal or foetal tissues. 6. Saccharin was not metabolized in vitro by liver microsomal preparations or faecal homogenates from rats kept on a normal diet or on a 1% saccharin diet for two years. 7. 2-Sulphamoyl[14C]benzoic acid given orally to rats was excreted unchanged more slowly than saccharin. It was not cyclized to saccharin in vivo.