Reviewed: Wei L, Luo Y, Zhang X, et al. Topical therapy with rhubarb navel plasters in patients with chronic constipation: Results from a prospective randomized multicenter study. J Ethnopharmacol. January 2021;264:113096. doi: 10.1016/j.jep.2020.113096.

Chronic constipation (CC) involves dysfunctional colonic stool movement and miscommunication within the anorectal neuromuscular apparatus and gut-brain axis, among other factors. A low-fiber diet, older age, dehydration, lack of exercise, and some drugs/medical procedures can increase the risk of CC. World prevalence of CC is 11-17%, with higher rates in Western nations. CC is prevalent in primary care settings and can impair patient quality of life and affect health systems financially. Remedies include a high-fiber diet, increased fluid intake, and various laxative agents. Adverse effects (AEs) and poor clinical responses can lead some patients to seek alternatives.

In traditional Chinese medicine (TCM), navel plasters (NPs) often are used for topical application of herbal preparations. With its thin epidermis, weak barrier function, and high concentration of blood vessels and nerves, the umbilical area is ideal for transdermal absorption. NPs allow patients to avoid the bitter taste of many oral medicines, circumvent the gastrointestinal tract, and do not disturb electrolyte balance.

Rhubarb (da huang; Rheum spp., Polygonaceae) roots, rhizomes, and stems are used in TCM for CC and other conditions. First recorded for medical use in China in the Shen Nong Ben Cao Jing, a medical text compiled during the Han Dynasty (206 BCE–220 CE), rhubarb is found in the Chinese, Korean, Japanese, and European pharmacopeias, among others. It often is used for pancreas protection.

Rhubarb root has been shown in previous studies to reduce inflammation, regulate intestinal flora, improve food tolerance, and relieve gastrointestinal dysfunction in critically ill patients. Clinical studies report that rhubarb supplementation can improve several defecation parameters and may be beneficial in intra-abdominal hypertension. Rhubarb NPs have been reported effective in relieving constipation in clinical practice, but this is the first prospective, randomized, placebo-controlled, multicenter clinical trial of their efficacy in CC, according to the authors.

The study was conducted at six hospitals in the People’s Republic of China from September 2016 to October 2017. Of 505 patients (18-85 years old) who were invited to participate, 374 agreed and were randomly assigned to either the rhubarb (n = 200) group or placebo (n = 174) group. Participants were blinded to their assigned agent until the end of the study; researchers were not. Inclusion was based on diagnosed constipation according to Rome III criteria. The authors excluded patients who had an abdominal mass or intestinal cancer, navel skin irritation or damage, mental or psychiatric diagnoses, or known hypersensitivity to study materials. Patients who were undergoing or scheduled to undergo general anesthesia within one week before or after the study, or who were pregnant or lactating, also were excluded.

Demographic characteristics were collected and patients’ Cleveland Constipation Score (CCS) and Bristol Stool Scale (BSS) were assessed at baseline. CCS was reassessed at study’s end, and BSS and AEs were recorded daily. Two or three nurses on each ward were trained to apply NPs. Participants who were hospitalized during their study participation were seen daily to monitor safety.

Rhubarb (R. officinale) root from Sichuan Province, China, was dried, powdered, and identified taxonomically by Kangmei Pharmaceutical Company (Shenzhen, China). High-performance liquid chromatography showed the powder’s main ingredients to be anthraquinones, including aloe-emodin, rhein, emodin, chrysophanol, and physcion. “Flour,” otherwise unidentified, was combined with food coloring for a placebo powder with a color like that of rhubarb. NPs with 1 g rhubarb or placebo powder were each mixed with 1 g honey made from lychee (Litchi chinensis, Sapindaceae) flowers and attached to patients’ navels with acupoint stickers (no supplier given) for six hours daily for eight days. The honey came from Nanning Quanjian Bee Farm (Guangxi, China).

The primary outcome measure was the “defecation condition” scored via CCS from day one to eight, with higher scores indicating more severe symptoms. Secondary outcome measures included fecal traits assessed daily via BSS and 24-hour defecation frequency. Of the 374 participants, 32 lacked data for baseline or one or more follow-ups (19 in rhubarb group, 13 in placebo group) and were excluded, leaving 342 participants (181 in rhubarb group, 161 in placebo group) for the per-protocol analysis. There were no significant differences between groups at baseline in demographic characteristics or in CCS, BSS, use of combined medications, feeding tube diet, patient autonomy, or underlying diagnoses. Participants’ mean age was 67.8 years, and 44.7% were women.

After eight days, the rhubarb group had significantly lower CCS compared to the placebo group (P < 0.05) and significantly greater defecation function compared to baseline (P < 0.001). No significant between-group difference was seen in number of defecations on days one through four or day seven, with significant differences on days five, six, and eight (P < 0.05 for each). From day five through eight, the rhubarb group had better scores for fecal morphology compared to placebo (P < 0.05 for each). All objective and subjective parameters improved in the rhubarb group over baseline and placebo. Study groups were stratified by age (< 50, 50-75, and > 75 years), and constipation relief was greater in participants under 75 years old (P < 0.05). It is unclear from the study if acupressure was a component of the treatment, based on the use of acupoint stickers in the application process.

AEs were reported for both rhubarb (e.g., nausea, vomiting, and diarrhea) and NPs (e.g., local blisters), but no serious AEs occurred in this study, with no significant difference between groups. A few participants in the rhubarb group reported transient diarrhea or abdominal pain.

The authors acknowledged that the study was limited by its single-blind design and short duration. It is also possible that the honey, which has been used medicinally for millennia, may have had some type of therapeutic effect.

The authors concluded: “[W]ith all clinical outcome parameters (CCS, defecating frequency, and BSS) demonstrating impressive symptom relief and improved quality of life, our results suggest that the rhubarb/honey navel plaster combination could be a promising candidate for the treatment of chronically constipated patients.”