- Gan cao
- sweet root
For Patients & Caregivers
Bottom Line: Licorice may be helpful in treating peptic ulcers, but it has not been shown effective in treating cancer.
In traditional Chinese medicine, licorice is often used in herbal formulas to harmonize the effects of other herbs. Experiments in animals and humans show licorice can mimic the effects of steroid hormones such as aldosterone and estrogen. The substance in licorice that scientists think is responsible for these effects is called glycyrrhizin. However, because glycyrrhizin causes undesirable side effects, it is often removed from licorice products during processing.
Physiologic activity has also been reported for several other compounds in licorice. Isoflavone compounds also mimic estrogens in the human body, and can kill several strains of bacteria and viruses on contact. Other compounds act as blood thinners and inhibit the process of inflammation. In humans, the compound, carbenoxolone, has been used to treat stomach and esophageal ulcers with positive effects. Scientists think that it increases blood flow to and amount of mucus lining the stomach.
- To treat bronchitis and chest congestion
No scientific evidence supports this use.
- To relieve constipation
This claim is not backed by research.
- To treat gastrointestinal disorders such as peptic ulcers
A substance in licorice called carbenoxolone decreased pain and heartburn and increased healing in patients with peptic ulcers, but major side effects (e.g., edema or fluid accumulation, low potassium, and high blood pressure) were reported.
- To treat hepatitis
Clinical trials in Japan have used a licorice extract (containing glycyrrhizin) to treat hepatitis B and C, and have shown that glycyrrhizin reduces liver disease. However, there is no proof that deglycyrrhizinated licorice would have the same effect.
- To reduce inflammation
Studies in animals support this use, but there is no proof from clinical trials that this effect occurs in humans.
- To relieve menopausal symptoms
Studies in animals show that licorice has estrogenic effects, and some of the components of licorice bind estrogen receptors. Human data are lacking.
- To treat microbial infections
Studies in animals suggest that licorice has anti-microbial activity, but human data are lacking.
- To treat prostate cancer
No scientific evidence supports this use. Licorice is an ingredient in PC-SPES, which has been studied in patients with prostate cancer.
This study was done to find out the efficacy and safety of STW 5-II, an herbal preparation, in releiving dyspepsia. The formula contains extracts of licorice root, matricaria flower, peppermint leaves, caraway, lemon balm, and bitter candy tuft. One hundred and twenty patients with functional dyspepsia were randomly assigned to 4 treatment groups and treated over a 12-week period. Patients received either STW 5-II or placebo for 8 weeks. Treatment during the last 4-week period was determined based on symptom relief in patients. Results showed that STW 5-II greatly improved symptoms of dyspepsia compared to a placebo. However, since STW 5-II contains other herbs, the extent to which licorice contributes to relieving dyspeptic symptoms is not clear from this study.
- You take cardiac glycosides (Licorice may increase their effects and cause toxicity).
- You take insulin (Licorice may have additive effects, possibly causing low blood levels of potassium and high levels of sodium retention in the body).
- You take warfarin or other blood thinners (Licorice may increase the risk of bleeding).
- You take MAO-inhibitors (MAO-Is) (Licorice may have additive effects).
- You take daunorubicin: Licorice intake can result in increased intracellular concentration of daunorubicin, which may increase its toxic effects.
- You are taking drugs that are substrates of Cytochrome P450 3A and 2D6 (Licorice may increase the risk of side effects of these drugs).
- You are taking Cyclosporine: Licorice greatly reduced the oral bioavailability of cyclosporine by activating P-gp and CYP3A4, which can make it less effective.
- You are taking Cortisol acetate:Licorice increased cortisol availability in tissues, which may increase its side effects.
- High blood pressure
- Muscle pain
- Cardiac arrhythmias
- Sodium retention
- Hypokalemia (low blood levels of potassium)
- Pseudo-hyperaldosteronism (causing low blood levels of potassium and high sodium retention)
- Decreased libido in men
- Suppression of scalp sebum secretion
- Thrombocytopenia (low blood platelet count)
For Healthcare Professionals
Licorice, derived from the root of the plant, has been used as a flavoring and sweetening agent. This herb is also an important component of traditional Chinese medicine used to detoxify and to enhance or balance the effects of other components in herbal formulas; and as a tonic, expectorant and a demulcent in Ayurveda. A number of compounds including glycyrrhizin are thought to account for its biologic activity.
In vitro and animal data show that licorice has antibacterial (2)(27), antiviral (48), anticancer (3)(4)(28)(29), anti-inflammatory (30), and hepatoprotective (49) properties.
Licorice also demonstrated estrogenic effects (7)(8)(10), reduced cardiotoxicity associated with doxorubicin (31) and improved the antitumor effects of cyclophosphamide (32). However, these effects have not been confirmed in humans.
Licorice demonstrated effectiveness in reducing dyspepsia (1) and hyperlipidemia (33) in clinical studies.
Glycyrrhizin has been reported to bind to glucocorticoid and mineralocorticoid receptors and exerts its effect via inhibition of 11b-hydroxysteroid dehydrogenase (12). Licorice can reduce serum testosterone by inhibiting 17-hydroxysteriod dehydrogenase (35)(36). Licorice contains isoflavones and other constituents that have estrogen receptor modulating activities (8)(10). The flavone and liquiritigenin components selectively activate ER-alpha (11).
Licorice demonstrated chemopreventive effects by modulating expression of the Bcl-2/Bax proteins, which act as apoptotic regulatory factors (3) and via inhibiting carcinogenesis (4).
In another study, licorice inhibited P-glycoprotein (P-gp), resulting in increased intracellular concentration of the chemo agent daunorubicin, which is a substrate of P-gp (34).
The most common side effect of licorice is hypokalemic hypertension, which occurs secondary to inhibition of 11beta-hydroxysteroid dehydrogenase, a renal enzyme, responsible for converting cortisol to cortisone. This inhibition results in enhancing the mineralocorticoid effects of cortisol (36) that include sodium retention and excretion of potassium.
Administration of licorice after meals delays the time (Tmax) to peak concentration, but does not affect maximum concentration (Cmax) or area-under-the-curve (AUC) (13). Elimination half-life is approximately 5 hours following intravenous administration (14). Primary route of excretion is via bile (15).
Reported: Hypertension (16)(45), lethargy, muscle pain, sodium retention, hypokalemia (17)(18)(19)(20)(26)(40)(41), adrenal crisis (21), ventricular fibrillation (22), cardiac arrythmias (23), carpal tunnel syndrome (24), glycyrrhizic acid poisoning (25), leukoderma (42) and thrombocytopenia (43) have been reported following use of licorice.
Cardiac glycosides: Licorice may potentiate toxicity (24).
Insulin: Licorice may have a synergistic effect possibly causing hypokalemia and sodium retention with concomitant use (38) .
Anticoagulants: Licorice may increase the metabolism and clearance of warfarin (19).
MAO-inhibitors (MAO-I): Licorice may potentiate activity of MAO-Is (37)(8)
P-Glycoprotein (P-gp) substrates: Licorice inhibited P-gp, resulting in increased intracellular concentration of the chemo agent daunorubicin, which is a substrate of P-gp (34).
Cytochrome P450 substrates: Glycyrrhizin, a major ingredient of licorice, induces CYP3A (39) and CYP2D6 (44), and can affect the intracellular concentration of drugs metabolized by this enzyme.
Cyclosporine: Licorice greatly reduced the oral bioavailability of cyclosporine by activating P-gp and CYP3A4 (46).
Cortisol acetate:Licorice increased cortisol availability in tissues in the hours following oral Cortisone acetate administration (47).
Madisch A, et al. Treatment of Functional Dyspepsia with a Herbal Preparation. A Double- Blind, Randomized, Placebo-Controlled, Multicenter Trial. Digestion 2004;69:45-52.
This study was aimed at determining the efficacy and safety of STW 5-II, an herbal preparation which contains icorice root as one of the major ingredients as well as matricaria flower, peppermint leaves, caraway, lemon balm, and bitter candy tuft. One hundred and twenty patients with functional dyspepsia were randomly assigned to 4 treatment groups and treated over a 12-week period. Patients received either STW 5-II or placebo for 8 weeks. Treatment during the last 4-week period was determined based on symptom relief in patients. The primary outcome measure was the standardized gastrointestinal symptom score (GIS). There was a significant decrease in GIS in patients treated with STW 5-II compared to those on placebo during the first 4 weeks. Symptoms improved further in patients who continued treatment during the second 4 weeks. After 8 weeks, 43.3% patients on active treatment and 3.3% patients on placebo reported total symptom relief. The authors suggest that STW 5-II significantly improves symptoms of dyspepsia as compared to a placebo. However, since STW 5-II contains other herbs, the extent to which licorice contributes to relieving dyspeptic symptoms is not clear from this study.