LITERATURE REVIEW Deglycyrrhizinated Licorice (DGL) for Gastrointestinal Ulcers: How Can Something So Good Be So Poorly Proven? By Tina Kaczor, ND, FABNO Licorice root has been widely used as herbal medicine dating back to at least 500 BC.1 Traditional applications across diverse cultures include as both a demulcent and an anti-inflammatory, often used to soothe respiratory or gastrointestinal (GI) symptoms. Modern botanical applications of the herb continue this tradition, with recommendations including the treatment of gastric ulcers, bronchitis, cough, and dyspepsia.2 While licorice is indispensable in these and many other herbal applications, it comes with a slight but measurable risk of side effects when used as a whole-root extract. One of the constituents in licorice root is glycyrrhizin, a triterpene glycoside that has been shown to have aldosterone-like effects.3 High doses or chronic consumption of glycyrrhizin from licorice root can create side effects that mimic a hypermineralcorticoid state. Clinically, this presents as electrolyte imbalances, hypertension, and possible cardiac abnormalities. While side effects are not common and risk is further minimized with monitoring of the patient and knowledge of proper dosing, removal of the glycyrrhizin compound eliminates the risk altogether. Today, deglycyrrhizinated licorice (DGL), which is specifically marketed for GI complaints, is a popular over-the-counter supplement. While DGL is popular for relieving gastric irritations, clinical trial support is weak. DGL exemplifies a widely accepted natural agent that “works” when assessed empirically but has yet to meet criteria for inclusion in an evidence-based, conventional medical paradigm. Modern History Modern medical history of licorice root begins in 1946, with the first article about “licorice juice” for gastric ulcers, published by Dutch physician F. E. Revers.4 Two years later he published a report on the use of licorice juice in the treatment of duodenal ulcers.5 While efficacy was demonstrated, side effects of edema, headaches, and cardiac complaints were also observed in these early applications of crude licorice extract. In 1950, J. G. Borst and colleagues proposed that the side effects were due to retention of sodium and water along with increased excretion of potassium and suggested the constituent glycyrrhizin (glycyrrhizinic acid) was to blame.6 By 1952, Revers had tried an extract of licorice with glycyrrhizic acid removed in a patient with peptic ulcer.7 He reported that removal of glycyrrhizin from the licorice extract resulted in the eradication of observed side effects. Reintroduction of whole root consumption in the same patient confirmed the hypermineralcorticoid side effects were indeed due to glycyrrhizin. Support for the Beneficial Effects of DGL Much of the in vitro data on licorice root is on glycyrrhizin, with less information available on the other constituents of licorice. For example, glycyrrhizin and its derivatives have been shown to effectively kill H. pylori strains, including those that are clarithromycin- or metronidazole-resistant. 8 Various flavonoids found in DGL have also been shown to be bactericidal toward H. pylori, and may account for some of the anti-ulcer activity preserved with the removal of glycyrrhizin. 9 In addition, DGL has demonstrated the ability to increase mucin, possibly by increasing the number of mucous secreting cells in the stomach.10 Perhaps the most suggestive evidence supporting DGL’s healing effect of GI mucosa is demonstrated through protection from aspirininduced GI bleeding. Rats given a large dose of DGL (2,000 mg/kg orally) demonstrated a reduction in aspirin-induced gastric lesions when the DGL was coadministered but not when it was given before aspirin ingestion. In this same study, DGL delivered intraperitoneally showed reductions of the gastric lesion scores, implying there may be a systemic component to the therapeutic effect. One human, placebocontrolled crossover study demonstrated that fecal blood loss induced by aspirin (375 mg three times daily) was significantly reduced with coadministration of DGL (175 mg/dose aspirin).11 DGL: Clinical Evidence to Date Four different licorice medicaments are used in clinical studies on ulcerative diseases, and differentiation among them is essential to an accurate review of the literature. The four include crude extracts of the whole plant, DGL combined with other agents (ie, Caved-S), DGL alone, and drug analogs of glycyrrhizin derivatives (eg, carbenoxolone, enoxolone). Many reviews, references, and marketing materials on DGL report on these four forms interchangeably. A closer look at this indiscriminate use of clinical trial data shows that they are not equivalents, and extrapolation of studies using agents containing glycyrrhizin or glycyrrhizin-like compounds are not relevant when compiling trial data on DGL. Crude extracts of licorice are a traditional use of the plant and led to the initial interest of Revers and others in proving its therapeutic use for ulcers. Since the crude extract contains glycyrrhizin, and glycyrrhizin has been shown to heal ulcerative lesions as a single agent, the efficacy of licorice crude extract can be assumed to be at least partly due to the glycyrrhizin content. DGL by definition is lacking glycyrrhizin; therefore its efficacy in ulcerative complaints must be proven independently from data on crude extracts. Carbenoxolone (Biogastrone™), a synthetic analogue of the biologically active metabolite of glycyrrhizin, β-glycyrrhetinic acid, is an approved drug in the United Kingdom and Europe for ulcers and aphthous stomatitis. Carbenoxolone and the newer analogue, enoxolone, both have a well-documented risk of inducing symptoms of a hypermineralcorticoid state. The induction of side effects with a ©2009 Natural Medicine Journal 1(3), November 2009 | Page 1 glycyrrhetinic acid analogue is to be expected, as glycyrrhizin and its metabolites have long been identified as the agents inducing these side effects.5 As synthetic analogues of the very constituent that was removed from DGL, there should be no extrapolation of clinical trial data derived from carbenoxolone or enoxolone as support or repudiation of DGL’s efficacy in ulcerative complaints. That leaves clinical trials with DGL as a single agent or DGL in combination with other compounds as the only relevant trials in an assessment of the clinical evidence. While trials of DGL as a single agent are ideal, the majority of published trials are on a combination product, Caved-S, in which DGL comprises 42% of the weight of each capsule. The components of Caved-S are DGL (380 mg), bismuth subnitrate (100 mg), aluminium hydroxide gel (100 mg), magnesium subcarbonate (200 mg), sodium bicarbonate (100 mg), frangula bark (30 mg), per tablet. It is essential to note that the term DGL is often used synonymously with Caved-S in the primary publications as well as in current reviews and marketing materials. For this reason, the form of the intervention used is included in the table summarizing the available trial data. (Table 1) There have been no new clinical trials on the use of DGL for ulcers in more than 20 years. The trials that have been published on Caved-S and DGL, as a whole, have been criticized for their lack of rigorous design. Most trials were small (the largest trial evaluated 96 patients). Not all trials were blinded, and many did not include a placebo control group, or the placebo was not adequately matched to the intervention group. Further, the natural course of ulcerative disease is one of exacerbation and remission, leading to a significant number of results in which participants experienced improvements regardless of the intervention. This makes a statistically significant improvement in the rate of healing difficult to obtain in trials with small numbers of patients. A comparison of the results derived from these trials provides conflicting results without trend or obvious conclusions able to be drawn. A cursory look at the summary of clinical trials (Table 1) shows no standard dosage, delivery, trial duration, or methodology used in the majority of trials. How efficacy was assessed varied between the trials as well with questionnaires, clinical observation, barium radiography, or endoscopic assessments used. Despite these many shortcomings, the results of some trials are intriguing enough to merit deeper exploration. The most impressive trial demonstrating benefit, published in 1973, enrolled 40 patients with more than six relapses of duodenal ulcer in the prior 12 months. The study clinic was also a surgical clinic, and all patients had been referred to the clinic for consideration of duodenal resection from a community physician. All patients had symptoms of unrelenting vomiting and/or pain on enrollment. Since these patients were severely ill, no placebo was offered; instead two levels of moderate and intense intervention with Caved-S was used. The moderate intervention included 8 tablets 8 times daily for 8 weeks, and intense intervention was 12 tablets 8 times daily for 16 weeks. While none of the patients required surgical intervention in the ensuing year, the cohort consuming the higher dosage for longer duration had significantly fewer symptomatic events during that year as well. Both groups used a dosage of Caved-S significantly higher than most trials, with a total DGL consumption of 4,560 mg/day in the high-dose group.12 In another trial by W. Larkworthy and colleagues, the intervention closely matched the above intervention of over 4 g daily, except it used DGL as a single agent and there was a mastication group to see if chewing conferred any benefit.13 This trial, which assessed patients endoscopically, did not show statistical difference in the healing of ulcers between the intervention and placebo groups. This may be due to the suggestion of five meals per day for all study participants. This frequency of eating increased the salivation of all participants, which has been independently proven to have an anti-ulcer effect.14 Further trials assessing the efficacy of these high doses are warranted to definitively answer the question of statistically significant effects of DGL. As an aside, Larkworthy and colleagues suggest that further trials must include endoscopic assessment, as symptoms do not always correlate with healing of ulcers. This suggests that licorice’s painrelieving abilities should be assessed separately from its ability to visibly increase the rate of healing in future trials. Why is there such a lack of trials in the past 20 years? With the advent of H2 blockers in the late 1970s and early 1980s, the medical management of ulcers changed dramatically, followed by the even more dramatic shift toward use of antibiotics after the widespread acceptance of the role of H. pylori in ulcer etiology in most patients in the 1990s. DGL was no longer being studied for up-front application in the healing of ulcers, but as maintenance therapy alone or with H2 blockage agents. Caved-S was demonstrated to be equivalent to cimetidine in the prevention of relapse in a two-year follow up study undertaken by A. G. Morgan and colleagues.15 Another study in 1987 showed DGL decreased the rate of relapse in patients taking ranitidine for gastric ulcers.16 The introduction and widespread usage of the proton pump inhibitors (such as omeprazole) further clouds the issue. This drug class has a more powerful acid suppression effect than the older class of H2 blockers, and there is no data on the use of DGL with proton pump inhibitors. Nevertheless, cumulatively the data suggest DGL may have a role in protecting the erosion of mucosa and decreasing relapse; therefore it deserves continued consideration for adjunctive management in these patients. Conclusion Deglycyrrhizinated licorice (DGL) is specifically used to promote the healing of ulcers and reduce ulcer-related symptoms. While it appears to be efficacious in this regard, the only clinical trials published using DGL as a treatment are poorly designed and/or were conducted more than 20 years ago. Well-designed, larger clinical trials may be helpful to delineate optimal dosage of DGL, as well as to determine which patient populations can derive the most benefit. Meanwhile, the incentive for the continued use of DGL will remain the anecdotal relief of symptoms—a strong impetus for both the clinician and the patient experiencing pain. Tina Kaczor, ND, FABNO, is a naturopathic physician board certified in naturopathic oncology. She received her naturopathic doctorate from National College of Natural Medicine, and completed her residency in naturopathic oncology at Cancer Treatment Centers of America in Tulsa, Okla. Dr. Kaczor received undergraduate degrees from the State University of New York at Buffalo. She is the current president of the Oncology Association of Naturopathic Physicians and secretary of the American Board of Naturopathic Oncology. She is adjunct faculty at National College of Natural Medicine as well as the Helfgott Research Institute in Portland, Ore. She has been published in several peer-reviewed journals and is the Medical Editor of the Natural Medicine Journal. 1 Shibata S. A drug over the millennia: pharmacognosy, chemistry, and pharmacology of licorice. Yakugaku Zasshi. 2000;120(10):849-862. 2 Blumenthal M. The ABC Clinical Guide to Herbs. Austin, TX: American Botanical Council; 2003:282-287. 3 Asl MN, Hosseinzadeh H. Review of pharmacological effects of Glycyrrhiza sp. and its bioactive compounds. Phytother Res. 2008;(6):709-724. 4 Revers FE. Does succus of licorice have a healing effect on the stomach ulcer? therapy. Ned Tijdschr Geneeskd. 1946;90:135-137. ©2009 Natural Medicine Journal 1(3), November 2009 | Page 2 5 Revers FE. The treatment of gastric ulcer and duodenal ulcer with licorice succus. therapy. Ned Tijdschr Geneeskd. 1948:92;2968-2973. 11 Rees WD, Rhodes J, Wright JE, Stamford LF, Bennett A. Effect of deglycyrrhizinated liquorice on gastric mucosal damage by aspirin. Scand J Gastroenterol. 1979;14(5):605-607. 6 Borst JG, Blomhert G, Molhuysen JA, Gerbrandy J, Turner KP, de Vries LA. Excretion of water and electrolytes during a 24-hour period and under influence of licorice extract. Acta Clin Belg. 1950;5(4):405-409. 12 Tewari SN, Wilson AK. Deglycyrrhizinated liquorice in duodenal ulcer. Practitioner. 1973;210(260):820-823. 7 Revers FE. Licorice juice without glycyrrhizinic acid in peptic ulcer therapy. Ned Tijdschr Geneeskd. 1952;96(38):2338-2341. 13 Larkworthy W, Holgate PF, McIllmurray MB, Langman MJ. Deglycyrrhizinised liquorice in duodenal ulcer. Br Med J. 1977;2(6095):1123. 8 Krausse R, Bielenberg J, Blaschek W, Ullmann U. In vitro anti-Helicobacter pylori activity of Extractum liquiritiae, glycyrrhizin and its metabolites. J Antimicrob Chemother. 2004;54(1):243-6. 14 Malhotra SL, Saigal ON, Mody GD. Role of saliva in the aetiology of peptic ulcer. Br Med J. 1965;1(5444):1220-1222. 9 Fukai T, Marumo A, Kaitou K, Kanda T, Terada S, Nomura T. Anti-Helicobacter pylori flavonoids from licorice extract. Life Sci. 2002;71(12):14491463. 15 Morgan AG, Pacsoo C, McAdam WA. Maintenance therapy: a two year comparison between Caved-S and cimetidine treatment in the prevention of symptomatic gastric ulcer recurrence. Gut. 1985;26(6):599-602. 10 van Marle J, Aarsen PN, Lind A, van Weeren-Kramer J. Deglycyrrhizinised liquorice (DGL) and the renewal of rat stomach epithelium. Eur J Pharmacol. 1981;72(2-3):219-225. 16 Morgan AG, Pacsoo C, Taylor P, McAdam WAF. Does Caved-S decrease the gastric ulcer relapse rate during maintenance treatment with ranitidine? Aliment Pharmacol Ther. 1987:1(6); 633-638. Table 1 Chronological Listing of Clinical Trials on DGL And Ulcers Journal Citation Gut. 1968; 9(1):48-51 Form of DGL used Caved-S Dosage Used Duration of Trial 2 tablets, 8 weeks, chewed 3 with times daily 4-week after meals crossover Gut. 1969; 10(4):299302 DGL 380mg/ capsule 2 capsules, 3 times daily after meals 4 weeks Gut. 1971; 12(6):449451 Caved-S 2 tablets, chewed 3 times daily after meals 4 weeks Br Med J. 1971; 3(5773): 501-503 DGL, 380 mg/ capsule 2 capsules, 3 times daily after meals 6 weeks Summary of Design Summary of Outcome Authors’ Conclusions Double-blind randomized controlled trial (RCT) of 6 gastric and 48 duodenal ulcer patients. Crossover was done in all gastric ulcer patients and 15/48 patients with duodenal ulcers. All patients were classified as “good,” “improved,” or “not improved” based on reported pain levels. Radiological imaging was also used before and after intervention. Usage of antacid was recorded in all patients. Double-blind RCT of 33 patients with radiographic evidence of gastric ulcerations greater than 10 mm2. Healing of ulcers was assessed through radiography. Double-blind, placebo-controlled study of 47 patients with active duodenal ulcer for a minimum of 6 months. Inclusion included baseline radiographic evidence of deformed duodenal bulb or ulcer niche as well as abdominal pain. Assessment was through symptom questionnaire. Intervention consisted of 4 weeks of treatment. Multicenter RCT in the United Kingdom. 90 men with recurrent duodenal ulcers. Symptoms assessed through patient reports and practitioner observation, fortnightly. Frequency of alkali medication for symptom relief was also tracked. Serum pepsinogen measured in both groups. Double-blind RCT with control group receiving carbenoxolone. 37 patients with radiographically confirmed gastric ulcers greater than 10mm2. All patients received antacid for 1 week prior to study participation. Assessments were done radiographically. All patients with gastric ulcers achieved symptomatic and radiographic improvements. There was less use of antacid in the Caved-S group and a trend toward improvements in observed symptoms in the duodenal ulcer intervention group. Followup imaging of duodenal ulcer patients suggests a spasmolytic effect of DGL at the level of the duodenal bulb. The group receiving DGL had an average reduction in ulcer size of 76%, versus 34% for the placebo group. No side effects were reported. There was no significant difference in symptom reports between the two groups. Electrolytes, complete blood count, blood urea nitrogen, and urinalysis were unchanged in both groups. No side effects were reported. “Duodenal ulcer patients showed marked improvements, with radiographical improvements in a few cases.” All gastric ulcer patients showed healing of ulcers. There appears to be a spasmolytic effect of DGL in patients with duodenal ulcers. No measurable difference in subjective pain reports. No difference in the amount of alkali medication consumed for symptomatic relief. No difference in practitioner reported observations of patient’s relief of symptoms. No change in serum pepsinogen levels. Br J Clin DGL 2 capsules, 4 weeks The group receiving carbenoxolone had Pract. 380 mg/ 3 times daily 100% of ulcers either reduce in size or 1972; capsule after meals heal completely. This compared to an 26(12):56385% response in patients receiving DGL. 566 There was no difference in the amount of antacids needed by the two groups throughout the trial. Practitioner. Caved-S 8 tablets, 8 One year Double-blind trial using two different doses None of the patients required surgical 1973; times daily for of Caved-S in 40 duodenal ulcer patients with intervention during the year of follow-up. 210(260): 8 weeks, or unremitting pain and greater than 6 relapses Most of the patients receiving 8 tablets 820-823 12 tablets, 8 in 12 months. Relapse was defined through the daily did have a relapse of symptoms times daily for presence of pain, and relapse-free defined by within the year. Patients receiving 12 16 weeks its absence. All patients had been referred for tablets daily did not suffer relapse. This surgical intervention. difference was statistically significant. Gut. 1973; DGL, 380 2 capsules, 8 weeks, Double-blind, placebo-controlled trial of 68 There was no statistical difference in the 14(9):711- mg/capsule taken orally 3 with patients with radiographically confirmed healing of the intervention group versus 715 times daily 4 week gastric ulcer(s). Assessment was done through placebo. crossradiographic follow-up. over DGL represents a therapeutic alternative to carbenoxolone without the risk of mineral corticoid side effects. There is no advantage to the addition of DGL in symptom management in patients with duodenal ulcers. There is no measurable advantage of DGL over placebo. The difference between carbenoxolone and DGL is statistically not significant. As it has no side effects, DGL represents a safe alternative to carbenoxolone. Higher doses of Caved-S confer a greater protection from relapse of duodenal ulcer symptoms. Caved-S demonstrated efficacy even in patients with severe, relapsing duodenal ulcers who were referred for surgical intervention. The location of the ulcer in the stomach, as well as the initial size, influences the healing time. With these considerations, previous studies showing efficacy may have had placebo groups unmatched to interventional groups. ©2009 Natural Medicine Journal 1(3), November 2009 | Page 3 Br Med J. 1977; 2(6095): 1123 DGL 450 mg/ capsule (Ulcedal) or 450mg/ block chew ing gum Br Med J. DGL 1978; (Ulcedal) 1(6106):148 450 mg/ capsule Gut. 1978; 19(9):779782 DGL (Ulcedal) 450 mg/ capsule 2 capsules, 8 weeks 5 times daily or 2 blocks, chewed for 30 minutes 5 times daily between meals 5 capsules 2 years daily Controlled trial of 34 patients with duodenal ulcers. DGL consumed as capsules or chewing gum versus placebo of either capsules or chewing gum of inert substance. Endoscopy was used to assess efficacy. There was no difference in healing of ulcers between the intervention group vs. placebo. The results do not support the concept of DGL usage in duodenal ulcer. Saliva introduced through chewing did not confer any benefit to healing either. Since symptoms do not correlate with healing, trials should be endoscopically controlled. Double-blind, placebo-controlled trial of 33 Relapse rates were 45% and 59% for the Although the results did not reach patients with healed gastric ulcerations. DGL and placebo groups respectively. This statistical significance, the need for Assessment was through gastroscopy and was not statistically significant. prophylaxis in this patient populabarium imaging every 6 months. Patients were tion lends itself to the use of DGL followed for up to 2 years. given the trend of less recurrence combined with a low toxicity profile. 2 capsules, 4 4 weeks Double-blind RCT of 96 patients with Median percentage change in the ulcer area This trial was designed to show a times daily endoscopy-verified gastric ulcers. Assessment was comparable in both groups. Symptom statistically significant benefit of was through repeat endoscopy and radiological improvement was also comparable in the DGL if there was a doubling of the assessment. Ulcer healing was defined as two groups. Endoscopic and radiographic assumed placebo-healing rate of re-epithelialization of lesion on visualization results had little concordance. 30%. It did not show this; therefore through gastroscopy. Radiographical healing there is no justification for continued was defined as disappearance of the ulcer use of DGL. crater on repeat imaging. Only clinical trials published in English with the full text available in electronic or hard copy are included above. NMJ OCT09 LR ©2009 Natural Medicine Journal 1(3), November 2009 | Page 4
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