[Prevention of irinotecan hydrochloride-induced diarrhea by oral administration of Lactobacillus casei strain Shirota in rats].

Irinotecan hydrochloride is an inhibitor of DNA topoisomerase I enzyme by its main active metabolite SN-38. However, irinotecan-induced severe diarrhea has often limited its more widespread use. We assessed the effect of oral administration of Lactobacillus casei strain Shirota (LcS) on irinotecan-induced diarrhea in rats. Rats in the LcS group were administered LcS (1.64 x 10(11) cfu/0.5 g/3 mL saline) orally for 28 days. Fourteen days later, irinotecan was given for 4 days (100 mg/kg i. p.). Control group rats were administered 3 mL saline orally for 28 days together with irinotecan, as in the LcS group. As a result, LcS significantly inhibited the weight decrease due to irinotecan and the food intake was greater than in the controls. The delayed diarrhea symptoms induced by irinotecan also seemed to be improved. Although we cannot conclude why LcS improved the side effect of irinotecan, LcS might inhibit beta-glucuronidase activity, which is produced by intestinal flora and plays a key role in the development of irinotecan-induced delayed diarrhea. Further investigations including this issue are warranted.