Table 1.
Summary of key preclinical studies of stimulant laxative toxicity (bisacodyl, senna).
| Citation | Study design | Duration | Key endpoints | Key findings | Conclusion |
|---|---|---|---|---|---|
| Genotoxicity/mutagenicity studies | |||||
| Heidemann et al., 1993 34 | Genotoxicity tests in vitro and in vivo on crude senna, senna extract, sennosides, rhein, and aloe-emodin | Not applicable |
In vitro tests: mouse spot test; CA in vivo; Ames/Salmonella sp.; Ames/E. coli; HGPRT; CA/CHO; MLA In vivo tests: CA/rat; MNT/rat; MNT/mouse; mouse spot test Ex vivo tests: UDS/rat |
Fructus sennae: negative (mouse spot; CA rat; MNT rat) Senna extract: positive (SAL; CHO); negative/equivocal (HGPRT) Sennosides: negative (SAL and E. coli/CHO/ML); negative (MNT mice) Rhein: negative (SAL; CHO); negative/equivocal (ML); negative in mouse MNT Aloe-emodin: positive (SAL; CHO), one positive and two negative tests (HGPRT); negative (mouse spot; CA/rat; MNT/mouse; rat UDS) |
Senna extracts and aloe-emodin were genotoxic in some in vitro tests; no genotoxic effect in in vivo tests Crude senna, sennosides, and rhein* were not genotoxic in in vitro or in vivo conditions |
| Mengs, 1988 35 | Mutagenicity testing of sennosides | Not applicable | Ames test (Salmonella typhimurium; E. coli); MLA; CHO; MNT | No effects (max concentration or dose) in the Ames test (5000 µg/plate), MLA (5000 µg/ml nonactivation; 1000 µg/ml with activation); CHO (5000 µg/ml nonactivation; 4000 µg/ml with activation); MNT (2500 mg/kg) | The sennosides tested were not mutagenic in the test systems employed |
| Brusick and Mengs, 1997 36 | Review article of genotoxic risk of senna [senna extract; sennosides (A, B, C, D)]; rhein; crude senna; aloe-emodin | Not applicable |
In vitro tests: Ames/Salmonella sp.; Ames/E. coli; MLA; HGPRT assay; CA/CHO; rat hepatocyte UDS; cell transformation (C3H/M2 cells) In vivo tests: MNT/rat; CA/rat bone marrow; somatic cell mutation/mouse; UDS/rat hepatocyte; MNT/mouse; CA/rat bone marrow metaphase |
Sennosides: negative (five tests) Rhein: negative (four tests); one test was equivocal (MLA) Senna extract: positive (Ames; CA); negative (HGPRT) Crude senna: negative (three in vivo tests) Aloe-emodin: positive in all in vitro tests (except in one HGPRT experiment); negative (four in vivo tests) |
Therapeutic doses of senna laxative produced in healthy human volunteers: aloe-emodin not detected in plasma (lower limit of quantification 0.5 mg/ml), using same assumptions for effects in rodents results in human safety margins for somatic genotoxicity of ~20,000 |
| NTP, 2001 37 | Genotoxicity studies on emodin | Not applicable |
In vitro tests: Ames/Salmonella sp; CA/CHO In vivo tests: MNT/rat bone marrow erythrocytes; MNT/mouse bone marrow erythrocytes; MNT/mouse peripheral blood erythrocytes |
Emodin was mutagenic in S. typhimurium strain TA100 with S9 activation (not in strain TA98 ± S9) CA was seen in CHO cells ± S9 Negative tests: rat bone marrow MNT; mouse bone marrow, and peripheral blood erythrocytes |
Mutagenicity potential did not result in carcinogenesis (see NTP, 2001 below) |
| Stoll et al., 2006 31 | Mutagenicity testing of bisacodyl | Not applicable | Micronucleus test: SHE test | Micronucleus test: no effect on percent PCEs SHE: No change in transformation frequency at any dose level |
Bisacodyl has no mutagenic potential |
| Inflammation, morphology, nerve damage | |||||
| Saunders et al., 1977 38 | Impact of bisacodyl on upper jejunum sections from humans, and jejunal, ileal, colonic areas in rats | Not applicable | Net water transport LM and EM of colon samples |
Bisacodyl induced net water secretion (p < 0.01) in human intestinal segments In rats: concentration-related inhibition of water absorption in all regions by bisacodyl; LM – focal alterations in surface absorptive cells; EM: mucosal damage |
Laxative effect of bisacodyl may be related to water absorption inhibition Morphological changes may be related to how bisacodyl decreases water transport |
| Carcinogenicity studies | |||||
| Lydén-Sokolowski et al., 1993 39 | Rat carcinogenicity study with a purified senna extract (sennosides) in drinking water | 2 years Daily doses consumed: 0, 5, 15, and 25 mg/kg |
Tumors – specifically GI tract, liver, kidneys, and adrenals | No treatment-related effects in macroscopic findings No differences in microscopic findings (high-dose group versus controls) No treatment-related increase in neoplasms |
There was no relationship between long-term administration of purified senna extract and tumor development of the GI tract, liver, kidneys, and adrenals of rats |
| Siegers et al, 1993 40 | To evaluate the tumorigenic potential of sennosides and aloin alone and their tumor-promoting potential in an established murine model of colorectal tumorigenesis (DMH) | 20 weeks DMH 20 mg/kg SC for 10 weeks. Sennosides 0.03% in diet (equivalent to 100 mg/kg/day – mild laxative effect) Aloin 0.03% in diet |
Colorectal tumors Hepatic and nephrotoxicity |
No. of tumor-bearing animals: senna only 0/20; senna + DMH 7/19; DMH alone 10/19; aloin alone 1/20; aloin + DMH 7/20 Incidence and growth of colorectal tumors were not affected by senna or aloin DMH-induced hepatotoxic and nephrotoxicity effects, which were enhanced by aloin but not senna |
DMH-induced colorectal tumors were not impacted by aloin or sennoside-enriched diets Aloin- and sennoside-fed mice had no significant changes in hepato- or nephrotoxicity |
| NTP, 2001 37 | Rat and mouse carcinogenicity studies with emodin via the die | 2 years Rat study: 0, 280, 830, or 2500 ppm emodin Mouse study: 0, 160, 312, or 625 ppm emodin in males and 0, 312, 625, or 1250 ppm emodin in females |
Tumors | Rat study: Zymbal gland carcinoma (three females, 2500 ppm), which exceeded current historical controls (equivocal finding); negative trends in mononuclear cell leukemia Mouse study: low incidences of renal tubule adenoma and carcinoma in male mice (one of each in the 312 and 625 ppm groups; rare tumor in male mice, possible association with emodin) |
No evidence of carcinogenic activity of emodin in male rats and female mice; equivocal evidence of carcinogenic activity in female rats and male mice |
| Borrelli et al., 2005 41 | Carcinogenicity study of senna pod extract in rats | 2 years Positive control AOM Senna pod extract (by gavage): 30 or 60 mg/kg on 6 days/week |
Tumors | Colon ACF and colon tumors: not present in controls or either dose of senna; present in all groups dosed with AOM; significantly decreased in AOM + senna pod extract versus AOM alone | Senna is devoid of carcinogenic potential in rats; senna may act as an anti-tumoral agent against colon carcinogenesis |
| Mitchell et al., 2006 42 | Rat carcinogenicity study with senna | 2 years Senna at 0, 25, 100, and 300 mg/kg/day (oral gavage) |
Tumors | Increased tubular basophilia and epithelial hypertrophy in the kidneys No alterations in the colonic nervous plexus or increase of cell proliferation in the large intestine No treatment-related neoplastic changes were observed in any organ examined |
Senna is not considered to be carcinogenic after daily administration for 2 years at doses up to 300 mg/kg/day in rats |
| Surh et al., 2013 43 | To assess carcinogenicity of senna in a haplo-insufficient mouse model | 40 weeks Senna fed in the diet at 0, 100, 300, 3000, 10,000 ppm |
Tumors | Significant increases in epithelial hyperplasia (males, females): cecum 10,000 ppm 22/25 and 19/25; colon 3000 ppm 3/24 (not significant) and 7/25, 10,000 ppm 25/25 and 25/25; rectum 10,000 ppm 1/25 and 1/25 (not significant) | Large intestine is the major target of senna-induced toxicity in wild-type and p53+/− mouse models No neoplastic changes seen |
| Borrelli et al, 2001 44 | Subchronic carcinogenic study in rats – to assess ability of bisacodyl and cascara in inducing ACF and tumors in the colon. | 13 weeks Positive control AOM Bisacodyl: 4.3 or 43 mg/kg/day on 6 days/week ± AOM Cascara: 140 or 420 mg/kg/day on 6 days/week ± AOM |
ACF and tumors in the colon | Both doses bisacodyl + AOM did not modify ACF appearance but increased number of crypts/focus versus AOM alone Cascara (both doses) + AOM – no increase in ACF or crypt/focus versus AOM alone AOM alone induced colon tumors as expected Neither bisacodyl nor cascara at either dose (absence of AOM) induced tumors Compared with AOM alone, low-dose bisacodyl and both cascara doses + AOM had no effect on tumors Compared with AOM alone, high-dose bisacodyl + AOM significantly increased number of tumors ~10-fold (of the nine rats in this group, 78% had tumors) |
When bisacodyl, at either dose, was given without AOM initiating treatment, there was no evidence of tumor development Bisacodyl has a possible promoting effect on colon rat carcinogenesis, particularly at diarrheal dose Cascara had no promoting or initiating activity at a laxative and diarrheagenic dose |
Sennosides are active components of senna; rhein is the active metabolite of senna; (aloe)-emodin is an anthraquinone (stimulant laxative). A more complete summary of these studies is available in Supplemental Table 1.
ACF, aberrant crypt foci; AOM, azoxymethane; CA, chromosome aberration test; CHO, Chinese hamster ovary cells; DMH, 1,2-dimethylhydrazine; EM, electron microscopy; GI, gastrointestinal; HGPRT, hypoxanthine-guanine phosphoribosyl transferase; LM, light microscopy; MLA, mouse lymphoma assay; MNT, micronucleus test; NTP, National Toxicology Program; PCE, polychromatic erythrocyte; ppm, parts per million; SAL, Salmonella test; SHE, Syrian hamster embryo test; S9, supernatant of liver homogenate; UDS, unscheduled DNA synthesis.