The effect of food, vitamin, or mineral supplements on chronic constipation in adults: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Over-the-counter supplements are commonly used to manage chronic constipation; however, their efficacy remains unclear. We aimed to investigate the effect of food, vitamin or mineral supplements on stool output, gut transit time, symptoms, and quality of life in adults with chronic constipation via a systematic review and meta-analysis of randomized controlled trials (RCTs).

METHODS

Studies were identified using electronic databases, backward citation, and hand-searching abstracts. RCTs reporting administration of food supplements (e.g., fruit extract supplements), vitamin or mineral supplements in adults with chronic constipation were included. Studies administering whole foods (e.g., fruits) were excluded. Risk of bias (RoB) was assessed with Cochrane RoB 2.0. Relative risks (RR), mean differences (MD), or standardized mean differences (95% confidence intervals [CI]) were calculated using a random-effects model.

KEY RESULTS

Eight RCTs (787 participants) were included, investigating kiwifruit (n = 3 RCTs), senna (n = 2), magnesium oxide (n = 2), Ziziphus jujuba (n = 1), and Malva Sylvestris (n = 1) supplements. Kiwifruit supplements did not impact stool frequency (MD 0.24 bowel movements/week [-0.32, 0.80]; p = 0.40) or consistency (MD -0.11 Bristol points [-0.31, 0.09], p = 0.29). Overall, 61% responded to senna and 28% to control; however, this did not reach statistical significance (RR 2.78, [0.93, 8.27]; p = 0.07). Overall, 68% responded to magnesium oxide and 19% to control (RR 3.32 [1.59, 6.92]; p = 0.001). Magnesium oxide improved stool frequency (MD 3.72 bowel movements/week [1.41, 6.03]; p = 0.002) and consistency (MD 1.14 Bristol points [0.48, 1.79]; p = 0.0007).

CONCLUSIONS AND INFERENCES

Magnesium oxide supplements are effective at improving cardinal symptoms of chronic constipation. Senna and kiwifruit supplements did not impact symptoms; however, findings were based on a small number of studies. Further research is required to investigate the effect of food supplements (e.g., kiwifruit supplements), as well as their whole food equivalents (e.g., whole kiwifruits) in chronic constipation.

Efficacy and tolerability of 1 L polyethylene glycol plus ascorbic acid with senna versus 2 L polyethylene glycol plus ascorbic acid for colonoscopic bowel preparation: Prospective, randomized, investigator-blinded trial

OBJECTIVES

Low-volume polyethylene glycol plus ascorbic acid (PEG-Asc) reduces the dosage of colonoscopic bowel preparation (BP) solution, but is still poorly tolerated. Adding laxatives to the BP solution reduces the volume of fluid required, without affecting quality. This study aimed to compare 1 L PEG-Asc plus 24 mg senna (1L-PEG/AS) and conventional 2 L PEG-Asc (2L-PEG/A) regimens on BP quality and patient tolerability.

METHODS

A single-center, randomized, investigator-blinded, noninferiority trial was performed between June and August 2022. Outpatients scheduled for colonoscopy were randomized (1:1) to the 1L-PEG/AS or 2L-PEG/A group. The Boston Bowel Preparation Scale (BBPS) was used to evaluate BP quality. Adverse events and tolerability were surveyed using questionnaires.

RESULTS

Overall, 344 patients received 1L-PEG/AS or 2L-PEG/A regimens. The baseline characteristics and adverse events of the two groups were comparable. The 1L-PEG/AS group showed noninferior adequate BP rates compared with the 2L-PEG/A group (88% vs. 89%, P = 1.00); overall BBPS was 7.1 ± 1.5 and 7.2 ± 1.5, respectively (P = 0.39). Higher willingness to repeat the BP was observed in the 1L-PEG/AS group (85% vs. 62%, P < 0.01).

CONCLUSIONS

The 1L-PEG/AS regimen was comparable to the 2L-PEG/A regimen in terms of BP adequacy, requiring lower BP solution volumes, with better patient tolerance. Thus, it may be a suitable alternative to the conventional BP solution for colonoscopy. The Japan Registry of Clinical Trials (jRCT1051220043).

American Gastroenterological Association-American College of Gastroenterology Clinical Practice Guideline: Pharmacological Management of Chronic Idiopathic Constipation

INTRODUCTION

Chronic idiopathic constipation (CIC) is a common disorder associated with significant impairment in quality of life. This clinical practice guideline, jointly developed by the American Gastroenterological Association and the American College of Gastroenterology, aims to inform clinicians and patients by providing evidence-based practice recommendations for the pharmacological treatment of CIC in adults.

METHODS

The American Gastroenterological Association and the American College of Gastroenterology formed a multidisciplinary guideline panel that conducted systematic reviews of the following agents: fiber, osmotic laxatives (polyethylene glycol, magnesium oxide, lactulose), stimulant laxatives (bisacodyl, sodium picosulfate, senna), secretagogues (lubiprostone, linaclotide, plecanatide), and serotonin type 4 agonist (prucalopride). The panel prioritized clinical questions and outcomes and used the Grading of Recommendations Assessment, Development, and Evaluation framework to assess the certainty of evidence for each intervention. The Evidence to Decision framework was used to develop clinical recommendations based on the balance between the desirable and undesirable effects, patient values, costs, and health equity considerations.

RESULTS

The panel agreed on 10 recommendations for the pharmacological management of CIC in adults. Based on available evidence, the panel made strong recommendations for the use of polyethylene glycol, sodium picosulfate, linaclotide, plecanatide, and prucalopride for CIC in adults. Conditional recommendations were made for the use of fiber, lactulose, senna, magnesium oxide, and lubiprostone.

DISCUSSION

This document provides a comprehensive outline of the various over-the-counter and prescription pharmacological agents available for the treatment of CIC. The guidelines are meant to provide a framework for approaching the management of CIC; clinical providers should engage in shared decision making based on patient preferences as well as medication cost and availability. Limitations and gaps in the evidence are highlighted to help guide future research opportunities and enhance the care of patients with chronic constipation.

Optimization and Validation of Dispersive Liquid-Liquid Microextraction for Simultaneous Determination of Aflatoxins B1, B2, G1, and G2 in Senna Leaves and Pods Using HPLC-FLD with Pre-Column Derivatization

Dispersive liquid-liquid microextraction (DLLME) was optimized for the simultaneous extraction of aflatoxins (AFB1, AFB2, AFG1, and AFG2) from powdered senna leaves and pods. Detection was performed using high-performance liquid chromatography with fluorescence detection (HPLC-FLD) and pre-column derivatization. The parameters affecting the DLLME extraction efficiency were evaluated. Chloroform (200 µL) was used as an extraction solvent, 500 µL of distilled water was used as a dispersive solvent, and the extraction was performed at pH 5.6 with no salt added. The optimized method was validated using leaves and pods according to the European Commission guidelines. The linear range for all aflatoxins was 2-50 µg/kg, with values for regression coefficients of determination exceeding 0.995. The recoveries of spiked senna leaves and pods were in the ranges of 91.77-108.71% and 83.50-102.73%, respectively. The RSD values for intra-day and inter-day precisions were in the ranges of 2.30-7.93% and 3.13-10.59%, respectively. The limits of detection and quantification varied in the ranges of 0.70-1.27 µg/kg and 2.13-3.84 µg/kg, respectively. The validated method was successfully applied for the quantification of aflatoxins in 60 real samples of dried senna leaves and pods.

Implementation of a Constipation Action Plan for Patients Discharged From a Pediatric Hospitalist Service

OBJECTIVE

The objective of this study was to determine the effect of a pharmacist-led constipation action plan on the rate of health care utilization.

METHODS

We conducted a prospective research study of patients 2 to 18 years of age admitted to a pediatric hospitalist service for constipation. A study pharmacist developed a patient-specific constipation action plan for each enrolled patient. Data were collected from the electronic medical record, patient/caregiver interview, and follow-up phone calls completed by a pharmacist. The primary outcome was to determine the effect of a pharmacist-led constipation action plan on the rate of health care utilization.

RESULTS

Twenty-seven patients were enrolled in the study. Median (range) age was 9 (2-18) years. Health care utilization of the entire study population decreased from approximately 8.7 encounters per month prior to implementation to approximately 3 encounters per month after implementation. Patients also reported an increase in daily bowel movements from approximately 1 per day prior to implementation to 2 per day post implementation.

CONCLUSIONS

Health care utilization appeared to decrease after implementation of a patient-specific, pharmacist-led constipation action plan.

Polyethylene Glycol Versus Senna for Bowel Preparation for Colonoscopy in Children: Updated Evidence by a Systematic Review and Meta-Analysis

For colonoscopy, bowel preparation, especially that using polyethylene glycol (PEG) or senna, is performed among children with gastrointestinal disorders; however, it is not fully grounded in evidence. This study reviewed via meta-analyses the approaches to bowel preparation for colonoscopy in children. Electronic databases and trial registries were searched until April 2021. Quality assessment was conducted using the Grading of Recommendations, Assessment, Development, and Evaluation method. In total, three randomized controlled trials (318 patients) were identified. PEG was observed as a preferred protocol of bowel preparation compared with senna (risk ratio [RR] 1.35, 95% confidence interval [CI] 1.05-1.74; I2 = 15%). It was less painful than senna (RR 0.62, 95% CI 0.44-0.87; I2 = 0%). No serious adverse events were noted. Overall, the certainty of the evidence was low to moderate. PEG might be a preferred preparation agent for colonoscopy in children. Given the limited data, more studies are recommended.

Efficacy of Lactulose versus Senna Plus Ispaghula Husk Among Patients with Pre-Dialysis Chronic Kidney Disease and Constipation: A Randomized Controlled Trial

Background

Constipation is a common problem among patients with advanced chronic kidney disease (CKD), leading to a loss of quality of life. Pharmacologic treatments are in common use, but whether lactulose and senna plus ispaghula husk is effecive to treat constipation among patients with pre-dialysis CKD remains unknown.

Objective

The aim of the study was to compare efficacy of lactulose and senna plus ispaghula husk to treat constipation among patients with pre-dialysis CKD.

Methods

A study was conducted among patients with pre-dialysis CKD receiving a diagnosis of constipation by ROME IV criteria. All subjects were randomly assigned to receive either lactulose or senna plus ispaghula husk daily for 14 days. After a 7-day washout period, the patients were switched to the other substance for another 14 days. Primary outcome was complete spontaneous bowel movement (CSBM) weekly, assessed using a stool diary after each laxative. Secondary outcome measure was the change of stool appearance using the Bristol stool form scale (BSFS).

Results

A total of 22 patients underwent randomization. Baseline CSBM and BSFS were 3.4 ± 1.4 and 2.3 ± 1.2 time/week, respectively. At the end of the study, the mean CSBM weekly increased in the lactulose group (mean difference 1.3 ± 1.6, P < 0.001) and the senna plus ispaghula husk group (mean difference 2.1 ± 2.1, P < 0.001) from baseline. Comparing CSBM between lactulose and senna plus ispaghula husk exhibited no significant difference (95% CI -1.2 to 0.06; P = 0.276). BSFS was significantly changed after using ispaghula husk with senna, the mean ± SD of BSFS changed to 1.7 ± 1.8 (p = 0.001) and after use lactulose, the mean ± SD of BSFS changed to 1.6 ± 1.8 (p = 0.001). No significant BSFS change was observed between groups regarding stool appearance. No serious adverse event in either group was found.

Conclusion

Lactulose and senna plus ispaghula husk were similar in efficacy to treat constipation among patients with pre-dialysis CKD.

Trial Registration

Thai Clinical Trials number is TCTR20200818006. Retrospectively Registered 18 August 2020.

Aquaporins Alteration Profiles Revealed Different Actions of Senna, Sennosides, and Sennoside A in Diarrhea-Rats

Senna and its main components sennosides are well-known effective laxative drugs and are used in the treatment of intestinal constipation in the world. Their potential side effects have attracted more attention in clinics but have little scientific justification. In this study, senna extract (SE), sennosides (SS), and sennoside A (SA) were prepared and used to generate diarrhea rats. The diarrhea rats were investigated with behaviors, clinical signs, organ index, pathological examination, and gene expression on multiple aquaporins (Aqps) including Aqp1, Aqp2, Aqp3, Aqp4, Aqp5, Aqp6, Aqp7, Aqp8, Aqp9, and Aqp11. Using qRT-PCR, the Aqp expression profiles were constructed for six organs including colon, kidney, liver, spleen, lung, and stomach. The Aqp alteration profiles were characterized and was performed with Principle Component Analysis (PCA). The SE treatments on the rats resulted in a significant body weight loss (p < 0.001), significant increases (p < 0.001) on the kidney index (27.72%) and liver index (42.55%), and distinguished changes with up-regulation on Aqps expressions in the kidneys and livers. The SS treatments showed prominent laxative actions and down regulation on Aqps expression in the colons. The study results indicated that the SE had more influence/toxicity on the kidneys and livers. The SS showed more powerful actions on the colons. We suggest that the caution should be particularly exercised in the patients with kidney and liver diseases when chronic using senna-based products.

Randomized controlled trial of 3 days fasting and oral senna, combined with mannitol and simethicone, before capsule endoscopy

BACKGROUND AND STUDY AIMS

The approach to small bowel preparation before capsule endoscopy (CE) is still suboptimal.

PATIENTS AND METHODS

One hundred eighty patients were randomly allocated to 3 groups. Patients in Group A took 250 mL 20% mannitol and 1 L 0.9% saline orally at 05:00 hours on the day of the procedure. In Group B the same preparation was taken at 20:00 on the day before, and at 05:00 on the day of CE; in addition, 20 mL oral simethicone was taken 30 minutes before CE. Group C was treated identically to Group B, except that the patients fasted for 3 days and took 3 g senna orally 3 times daily before CE. The length of bowel containing green luminal contents was assessed by ImageJ software and bowel cleanliness was evaluated by computed assessment of the cleansing score.

RESULTS

Cleansing of the whole small bowel and the distal small bowel were significantly different between the 3 groups (χ = 22.470, P = .000; χ = 17.029, P = .000, respectively). There were also significant differences between the 3 groups in the length of small bowel and specifically the length of the distal small bowel containing green luminal contents (χ = 12.390, P = .000, χ = 15.141, P = .000, respectively), but not with regard to the proximal small bowel (χ = 0.678, P = .509).

CONCLUSIONS

Three days fasting and oral senna, combined with 20% mannitol and simethicone, before CE, can reduce the effects of bile on the small bowel and improve small bowel cleansing, especially in the distal small intestine.

Validation of a QuEChERS-based gas chromatographic method for analysis of pesticide residues in Cassia angustifolia (senna)

A simple multi-residue method based on modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) approach was established for the determination of 17 organochlorine (OC), 15 organophosphorous (OP) and 7 synthetic pyrethroid (SP) pesticides in an economically important medicinal plant of India, Senna (Cassia angustifolia), by gas chromatography coupled to electron capture and flame thermionic detectors (GC/ECD/FTD) and confirmation of residues was done on gas chromatograph coupled with mass spectrometry (GC-MS). The developed method was validated by testing the following parameters: linearity, limit of detection (LOD), limit of quantification (LOQ), matrix effect, accuracy-precision and measurement uncertainty; the validation study clearly demonstrated the suitability of the method for its intended application. All pesticides showed good linearity in the range 0.01-1.0 μg mL(-1) for OCs and OPs and 0.05-2.5 μg mL(-1) for SPs with correlation coefficients higher than 0.98. The method gave good recoveries for most of the pesticides (70-120%) with intra-day and inter-day precision < 20% in most of the cases. The limits of detection varied from 0.003 to 0.03 mg kg(-1), and the LOQs were determined as 0.01-0.049 mg kg(-1). The expanded uncertainties were <30%, which was distinctively less than a maximum default value of ±50%. The proposed method was successfully applied to determine pesticide residues in 12 commercial market samples obtained from different locations in India.

Two low-dose bowel-cleansing regimens: efficacy and safety of senna and sodium phosphorus solution for colonoscopy

BACKGROUND

The aim of the present study was to compare the efficacy, adequacy, side effects, and patient compliance of sodium phosphorus (NaP) and senna solutions when preparing the colon before colonoscopy.

METHODS

A total of 137 consecutive patients who were considered for colonoscopy evaluation had randomly received one of two premeditated regimens: 90 mL of oral NaP (NaP group) or 500 mL of 1,000 mg of sennosides A and B calcium +66.6 g of sorbitol (senna group). Patients' compliance with the bowel-cleansing method was determined using a questionnaire prior to the colonoscopic examination. On the other hand, the adequacy of the bowel-cleansing method was evaluated by the colonoscopist who was blind to the bowel-cleansing regimen used prior to the examination of the colon from the rectum to the cecum.

RESULTS

Nausea and vomiting complaints were seen more frequently in the NaP group than in the senna group (47 vs 28 and 31 vs 10; P<0.05 and P<0.01, respectively). The response to the question of whether the patients would like to use the same regimen again or not was similar in both groups. The acceptable bowel-cleansing rate was also comparable across both groups. Nevertheless, the number of patients that experienced excellent bowel cleansing in terms of general appraisal of the colonoscopic evaluation was significantly greater in the NaP group than in the senna group (46 vs 25; P<0.001).

CONCLUSION

Although bowel cleansing was better in the NaP group, both cleansing regimens were comparable regarding the admissibility of the preparations for the procedure. The senna regimen is, however, superior to the NaP regimen in terms of application compliance and its side effects, and it may be an effective alternative for cleansing the bowel prior to colonoscopic examination.

Comparative effectiveness of senna to prevent problematic constipation in pediatric oncology patients receiving opioids: a multicenter study of clinically detailed administrative data

CONTEXT

Pediatric oncology patients often receive prolonged courses of opioids, which can result in constipation.

OBJECTIVES

Comparing patients who received senna matched with similar patients who received other oral bowel medications, determine the subsequent risk of "problematic constipation," assessed as the occurrence of the surrogate markers of receiving an enema, escalation of oral bowel medications, and abdominal radiographic imaging.

METHODS

This was a retrospective cohort study of hospitalized pediatric oncology patients less than 21 years of age in 78 children's and adult hospitals between 2006 and 2011 who were started on seven consecutive days or more of opioid therapy and were started on an oral bowel medication within the first two days of opioid therapy. Clinically detailed administrative data were used from the Pediatric Health Information System and the Premier Perspective Database. After performing propensity score matching of similar patients who started senna and who started a different oral bowel medication, Cox regression modeling was used to compare the subsequent hazard of the surrogate markers.

RESULTS

The final matched sample of 586 patients averaged 11.5 years of age (range 0-20 years); 41.8% (n = 245) had blood cancer, 50.3% (n = 295) had solid tumor cancer, and 7.9% (n = 46) had brain cancer. Initiating senna therapy within two days of starting the prolonged opioid course, compared with initiating another oral bowel medication, was significantly associated with a lower hazard during the ensuing five days for receipt of an enema (hazard ratio [HR], 0.31; 95% CI, 0.11-0.91) or undergoing abdominal radiographic imaging (HR, 0.74; 95% CI, 0.55-0.98), was marginally associated with a lower hazard of oral bowel medicine escalation (HR, 0.78; 95% CI, 0.59-1.03), and overall was significantly associated with a lower hazard of the composite end point of problematic constipation (HR, 0.70; 95% CI, 0.56-0.88).

CONCLUSION

Initiating senna therapy, compared with other oral bowel medications, diminishes the subsequent risk of surrogate markers of problematic constipation in this population.

Efficacy and safety of gum chewing in adjunct to high-dose senna for bowel cleansing before colonoscopy: a single-blind randomized controlled trial

BACKGROUND/AIMS

Inadequate bowel cleaning leads to a suboptimal colonoscopic examination. Gum chewing has been reported to have a favorable effect on postoperative bowel functions. We conducted this study to establish if gum chewing added to high-dose senna before colonoscopy promotes bowel cleaning.

PATIENTS AND METHODS

In this randomized controlled study, consecutive outpatients scheduled for elective colonoscopy were randomized into two groups. Group 1 patients (n = 65) used senna solution 150 mL (300 mg senna) the night before colonoscopy. The patients also used sennoside tablet 80 mg daily for 3 days before the colonoscopy. Patients in group 2 (n = 64) were additionally advised to chew sugarless gum half an hour three-times daily after meals for these 3 days. The overall quality of colonoscopy cleaning was evaluated using the Aronchick scale by a single endoscopist who was blinded to the intervention. Difficulty of procedure, patients' tolerance, and adverse events were also evaluated.

RESULTS

A total 129 patients were enrolled in the study. Superior cleaning was found in gum chewing group when compared with other group particularly in the cecum and ascending colon. Cecal intubation time was significantly shorter in the gum-chewing group (8.6 ± 5.1 and 7.1 ± 2.8 min, P = 0.03). Adverse events were more common in group 1 compared to the gum-chewing group.

CONCLUSIONS

Gum chewing enhances colonoscopy bowel preparation quality. Moreover, it is a physiologically sound, safe, and an inexpensive part of the colonoscopy bowel preparation. Gum chewing could be advised in addition to high-dose senna containing bowel preparation.

Toxicology and carcinogenesis study of senna in C3B6.129F1-Trp53 tm1Brd N12 haploinsufficient mice

Senna is a pod or leaf of Senna alexandrina P. Mill and is used as a stimulant laxative. In the large intestine, bacterial enzymes reduce sennosides to rhein-9-anthrone, the active form for the laxative effect. To determine the potential toxic effects of senna, a 5-week dose range finding study in the C57BL/6N mouse and a 40-week toxicology and carcinogenesis study in the C3B6.129F1-Trp53 (tm1Brd) N12 haploinsufficient (p53(+/-)) mouse were conducted. In the 5-week study, C57BL/6N mice were exposed to up to 10,000 ppm senna in feed. Increased incidences of epithelial hyperplasia of the cecum and colon were observed in males and females exposed to 5,000 or 10,000 ppm senna. These intestinal lesions were not considered to be of sufficient severity to cause mortality and, thus, in the p53(+/-) mouse 40-week study, the high dose of 10,000 ppm was selected. Significant increases in the incidences of epithelial hyperplasia of the colon and cecum were observed at 10,000 ppm in p53(+/-) males and females, and the incidence of hyperplasia of the colon was significantly increased at 3,000 ppm in females. In conclusion, the large intestine was the major target of senna-induced toxicity in both wild-type and the p53(+/-) mouse model. There was no neoplastic change when senna was administered to p53(+/-) mouse.

Effect of sodium rhein on electrically-evoked and agonist-induced contractions of the guinea-pig isolated ileal circular muscle

1. This study examined the effects of sodium rhein (0.03-30 microM) on the contractions of the isolated circular muscle of guinea-pig ileum induced by acetylcholine (100 nM), substance P (3 nM) and electrical stimulation (10 Hz for 0.3 s, 100 mA, 0.5 ms pulse duration). The effect of sodium rhein was also evaluated on the ascending excitatory reflex using a partitioned bath (oral and anal compartments). Ascending excitatory enteric nerve pathways were activated by electrical field stimulation (10 Hz for 2 s, 20 mA, 0.5 pulse duration) in the anal compartment and the resulting contraction of the guinea-pig intestinal circular muscle in the oral compartment was recorded. 2. Sodium rhein (0.3, 3 and 30 microM) significantly potentiated (52+/-11% at 30 microM) acetylcholine-induced contractions. In the presence of tetrodotoxin (0.6 microM) or omega-conotoxin GVIA (10 nM) sodium rhein (3 and 30 microM) did not enhance, but significantly reduced (49+/-10% and 44+/-8%, respectively, at 30 microM) acetylcholine-induced contractions. 3. Sodium rhein (0.3, 3 and 30 microM) significantly increased (65+/-11% at 30 microM) substance P-induced contractions. In the presence of tetrodotoxin (0.6 microM), omega-conotoxin GVIA (10 nM) or atropine (0.1 microM), sodium rhein (3 and 30 microM) significantly reduced (50+/-10%, 55+/-8% and 46+/-10%, respectively, at 30 microM) substance P-induced contractions. 4. NG-nitro-L-arginine methyl ester (L-NAME, 100 microM) abolished the potentiating effect of sodium rhein on acetylcholine and substance P-induced contractions. At the highest concentration (30 microM), sodium rhein, in presence of L-NAME, reduced the acetylcholine (30+/-6%)- or substance P (36+/-6%)-induced contractions. 5. Sodium rhein (30 microM) significantly potentiated (29+/-9%) the electrically-evoked contractions. L-NAME (100 microM), but not phentolamine, enhanced the effect of sodium rhein. Sodium rhein (30 microM) significantly increased (32+/-9%) the ascending excitatory reflex when applied in the oral, but not in the anal compartment. 6. These results indicate that sodium rhein (i) activates excitatory cholinergic nerves on circular smooth muscle presumably through a facilitation of Ca2+ entry through the N-type Ca2+ channel, (ii) has a direct inhibitory effect on circular smooth muscle and (iii) does not affect enteric ascending neuroneural transmission. Nitric oxide could have a modulatory excitatory role on sodium rhein-induced changes of agonist-induced contractions and an inhibitory modulator role on sodium rhein-induced changes of electrically-induced contractions.