Abstract
Absorption, metabolism and excretion of lactitol were studied in rats and dogs after intravenous or oral administration of 14C-lactitol.
1. After intravenous administration, almost all the radioactivity in plasma was due to the unchanged form. 14C-Lactitol was eliminated from plasma with half-lives of 0.352 hr in rats and 0.594 hr in dogs.
2. After oral administration, the plasma levels of radioactivity reached maximum level 6.0 hr in rats and 9.3 hr in dogs, then decreased slowly. Most of the radioactivity was due to metabolites of 14C-lactitol, and the unchanged form was hardly detected in plasma. Systemic availabilities, based on plasma concentration of 14C-lactitol, were 1.69% in rats and 2.72% in dogs.
3. After oral administration to rats, plasma levels of radioactivity increased proportionally to administered dose (10 ?? 1000 mg/kg). There were no clear differences in plasma radioactivity between male and female rats.
4. After oral administration to rats, most of radioactivity was present as the unchanged form in the small intestine, but as metabolites such as sorbitol and volatile substances (probably short chain fatty acids) in the cecum. Therefore, it is suggested that lactitol is greatly metabolized in rat cecum by intestinal microflora.
5. After intravenous administration to rats and dogs, most of the administered radioactivity was excreted in urine as the unchanged form. After oral administration to rats, the excretion of radioactivity within 168 hr was 5.1, 16.1 and 65.0% of dose into urine, feces and expired air, respectively.
6. The protein binding of lactitol in vitro was investigated in rat, dog and human serum, but it was not bound to serum protein at the concentration range of 0.5 to 50 μg/ml.
