[13-week oral toxicity study of lactitol (NS-4) in rats followed by 5-week recovery test].

Twenty male and 20 female Slc : SD rats were orally given lactitol, a hepatic encephalopathy drug, for 13 weeks at doses of 0, 0.625, 2.5 or 10 g/kg/day. A 5 week recovery test was conducted after the discontinuation of the drug treatment. Soft stool and decreased food consumption were seen in the 2.5 and 10 g/kg groups. In the 10 g/kg group, there were diarrhea, soiled fur, abdominal distention, salivation, piloerection, decreased body weight gain and increased water consumption. Urinalysis showed decreased urine volume and K+ excretion in the 10 g/kg group. In this dose group, biochemical examination showed decreased ALP, total cholesterol, triglyceride, glucose, Ca, Na+, Cl- and total protein. In the pathological examination, the cecum weight was increased in all dose groups. In the 2.5 and 10 g/kg groups, cecum distention with mucosal hyperplasia was observed. The adrenal weight was increased in the 10 g/kg group and hypertrophy of zona fasciculata of adrenal gland were seen in the 2.5 and 10 g/kg groups. The thymic weight was decreased in the 10 g/kg group. Ophthalmoscopic and hematologic examinations failed to reveal any drug induced changes. The increased cecum weight in the 0.625 g/kg group was regarded as toxicologically insignificant because of the failure of the association with any clinical or morphological findings. The above mentioned changes were satisfactorily reversible except for those in the cecum. Based on the results obtained, the NOAEL of this study was suggested to be 0.625 g/kg/day.