Chronic sennoside treatment does not cause habituation and secondary hyperaldosteronism in rats

Rats were treated with sennosides (6 x 10, 6 x 40 or 2 x 30 mg/kg weekly) or with danthron (6 x 500 mg/kg weekly) for 6 months. The laxative effect as measured by faecal wet weight during the first 10 h after treatment increased 3- to 4-fold by the higher sennoside doses (daily or intermittently) and 1- to 3-fold by danthron. The low sennoside dose had no measurable effect except on the 1st day (2 fold) compared with the control group. Mean faecal water content increased from 53% (controls) to 66-79% in rats treated with high sennoside doses and to 57 (1st day) -69% in danthron-treated rats. Serum aldosterone levels and mucosal Na(+)-K(+)-ATPase activities in the small intestine and colon did not change with treatment. There were no signs of habituation or secondary hyperaldosteronism due to sennosides or danthron in spite of chronic diarrhoea over 6 months.