Actionable Intelligence
Compound: glycyrrhizin (glycyrrhizic acid; the study used glycyrrhizic acid monoammonium). Source study: Ohnishi et al., J Clin Biochem Nutr 2026, 79(1): 104-110.
1. The Translational Protocol
Human Equivalent Dose, body surface area normalisation
FDA guidance formula:
HED (mg/kg) = Animal dose (mg/kg) x (Animal Km / Human Km)
Km values from the FDA table: mouse Km = 3, human (60 kg adult) Km = 37.
Step by step:
- Animal dose in the study: 15 mg/kg, oral gavage, three times per week
- Km ratio: 3 / 37 = 0.081
- HED per administration: 15 x 0.081 = 1.22 mg/kg
- For a 60 kg adult: 1.22 x 60 = 73 mg per dose
- For a 70 kg adult: 1.22 x 70 = 85 mg per dose
- For a 80 kg adult: 1.22 x 80 = 97 mg per dose
- Weekly exposure for a 70 kg adult: 85 x 3 = 256 mg per week
- Averaged daily exposure: 256 / 7 = 36.5 mg per day, equal to 0.52 mg/kg per day
Cross-check against the human no-effect level. The Scientific Committee on Food identifies a NOAEL of 2 mg/kg body weight per day, roughly 130 mg per person per day, from the Bijlsma and van Gelderen human volunteer work, and sets a provisional upper limit of 100 mg per day of glycyrrhizic acid from all sources.
- On an averaged daily basis: 0.52 against a NOAEL of 2 mg/kg/day, a margin of about 3.8 fold
- On a dosing-day basis: 1.22 against 2 mg/kg/day, a margin of about 1.6 fold
That is a thin margin for a chronic protocol, and it is a margin against an endocrine effect that has no therapeutic upside. The 85 mg per dose figure sits just under the 100 mg per day advisory ceiling, so a person taking this three times a week is operating at roughly one third of the regulatory ceiling on average and at 85 percent of it on dosing days.
Salt-form note: the study used glycyrrhizic acid monoammonium (molecular weight about 840) rather than the free acid (about 822). The correction is under 3 percent and does not change any conclusion.
Caveat on the method itself: BSA normalisation is a first-in-human starting-dose heuristic from FDA guidance. It does not account for the species difference that matters most here, which is that rodents are markedly less sensitive to 11-beta-HSD2 inhibition than humans are. The true human-equivalent risk at this dose is higher than the arithmetic suggests.
Guidance for industry: estimating the maximum safe starting dose in initial clinical trials for therapeutics in adult healthy volunteers, FDA (2005), A simple practice guide for dose conversion between animals and human (2016), Opinion of the Scientific Committee on Food on glycyrrhizinic acid and its ammonium salt (2003)
Pharmacokinetics
-
Oral bioavailability of glycyrrhizin as such: poor. Glycyrrhizin is barely absorbed intact from the gastrointestinal tract. It requires hydrolysis by intestinal bacterial beta-glucuronidase to 18-beta-glycyrrhetinic acid, which is then almost completely absorbed. This is the single most important PK fact for anyone reading the mechanism section, because the systemic species is glycyrrhetinic acid, not the HMGB1-binding parent molecule.
-
Absorption of the metabolite: near complete once formed, but formation is microbiome dependent. Gut microbiome perturbation changes glycyrrhizic acid bioavailability in rats.
-
Tmax: highly variable. After a 600 mg oral dose the circulating glucuronide metabolite peaked anywhere from 1.5 to 39 hours later, reflecting the bacterial activation step and enterohepatic recycling.
-
Elimination: slow and multi-peaked. Plasma concentrations show several peaks over roughly 50 hours from enterohepatic recirculation, and complete elimination of glycyrrhetic acid takes several days. Only 0.31 to 0.67 percent is excreted in urine; elimination is predominantly biliary.
-
Practical consequence: a “three times a week” schedule does not produce washout between doses. Effective exposure is closer to continuous than intermittent, which matters because the mineralocorticoid effect is cumulative, and because the intermittent-dosing rationale that makes rapamycin tolerable does not transfer here.
-
Single clean half-life value: not available in the sources retrieved. The literature reports multi-compartment behaviour rather than a single terminal half-life. Treat any single number you see quoted with suspicion.
Intestinal bacterial hydrolysis is indispensable to absorption of 18-beta-glycyrrhetic acid after oral administration of glycyrrhizin in rats (1994), Bioavailability study of glycyrrhetic acid after oral administration of glycyrrhizin in rats (1996), The effect of gut microbiome perturbation on the bioavailability of glycyrrhizic acid in rats (2025), Analysis and pharmacokinetics of glycyrrhizic acid and glycyrrhetinic acid in humans and experimental animals (1994), Hazard assessment of glycyrrhizic acid from liquorice, VKM Report 2018:09
Safety and Toxicity
Acute toxicity (LD50). Oral LD50 in rats is 14.2 g/kg (males) and 18.0 g/kg (females). In mice it exceeds 7.5 g/kg for both sexes. Glycyrrhizate salts in mice span 1,220 to 12,700 mg/kg. Acute toxicity is effectively a non-issue; this compound does not kill by overdose at anything resembling a supplement dose.
Chronic toxicity. A 96-week mouse study at up to 407 mg/kg showed no evidence of chronic toxicity or tumourigenicity. Short-term rat studies showed minor red cell and hepatic enzyme changes with a no-effect level of 0.31 to 0.63 g extract/kg. The organ toxicity profile is benign. The problem is not organ toxicity, it is endocrine.
NOAEL, the number that actually governs use: 2 mg/kg body weight per day in humans, roughly 130 mg per person per day, from human volunteer studies, based on potassium depletion as the endpoint. The SCF’s provisional upper intake limit is 100 mg per day. Pharmacokinetic modelling predicts roughly 4 per 10,000 exposed people will show pseudohyperaldosteronism symptoms at that 100 mg per day limit, and the SCF explicitly flags that subgroups including hypertensives and people with genetic 11-beta-HSD2 variants are not protected by it.
Phase I and controlled human safety data. These exist, and they are informative because they come from a licensed pharmaceutical product rather than from supplement use.
- A double-blind randomised placebo-controlled phase I/II trial of intravenous glycyrrhizin in chronic hepatitis C was conducted and published in 1999.
- Stronger Neo-Minophagen C is a licensed intravenous glycyrrhizin preparation in Japan and elsewhere for abnormal hepatic function in chronic liver disease. Each 2 mL ampoule delivers 4 mg glycyrrhizin; the daily regimen is 40 to 60 mL, that is 80 to 120 mg glycyrrhizin intravenously per day, maximum 100 mL, that is 200 mg.
- Registration-dossier clinical data for that product report hypokalaemia in 7.5 percent and hypertension in 4.4 percent of treated hepatic-disease patients.
- Listed serious adverse reactions: pseudoaldosteronism with severe hypokalaemia, hypertension, sodium and fluid retention, oedema; hypokalaemic myopathy; rhabdomyolysis (reported with oral preparations); rare shock.
- Contraindications: aldosteronism, myopathy, hypokalaemia, prior hypersensitivity.
Read that in context. At an intravenous dose roughly in the same range as the calculated HED, in a monitored clinical population, roughly 1 in 13 patients develops hypokalaemia and roughly 1 in 23 develops hypertension. That is your real-world adverse event rate. It is not rare.
Meta-analytic human effect at or above 100 mg per day: systolic blood pressure +5.45 mmHg (95 percent CI 3.51 to 7.39), diastolic +3.19 mmHg (95 percent CI 0.10 to 6.29), plasma potassium −0.33 mmol/L (95 percent CI −0.42 to −0.23), across 18 studies and 337 subjects, with dose-response correlation r squared 0.55 systolic and 0.65 diastolic.
Liver and kidney signals. Hepatically the signal is favourable, not adverse: glycyrrhizin preparations lower transaminases in chronic liver disease and have been used for decades on that basis. Renally the drug does not appear directly nephrotoxic, but the mineralocorticoid effect causes sodium and water retention and potassium wasting, and severe cases produce hypokalaemic nephropathy and acute kidney injury secondary to rhabdomyolysis. The paper’s claim of renal protection in mice must be set against a documented human renal-endocrine liability.
Hazard assessment of glycyrrhizic acid from liquorice, VKM Report 2018:09, Opinion of the Scientific Committee on Food on glycyrrhizinic acid (2003), Intravenous glycyrrhizin for the treatment of chronic hepatitis C: a double-blind, randomized, placebo-controlled phase I/II trial (1999) (publisher returned 403 on direct fetch; record located via live search), Stronger Neo-Minophagen C assessment report, composition, dosing and adverse reactions, The association between consistent licorice ingestion, hypertension and hypokalaemia: a systematic review and meta-analysis (2017), Liquorice toxicity: a comprehensive narrative review (2023), Final report on the safety assessment of glycyrrhetinic acid and glycyrrhizates, CIR (2007)
CYP450 and transporter interactions
-
CYP3A: modest induction, and it is clinically relevant by bioequivalence criteria. In 16 healthy men in a randomised crossover design, 14 days of glycyrrhizin followed by midazolam on day 15 reduced midazolam AUC from 196.4 to 151.3 ng·h/mL, geometric mean ratio 0.77 (90 percent CI 0.70 to 0.89), Cmax ratio 0.83 (90 percent CI 0.74 to 1.01). The authors called it a modest but clinically relevant induction. Translation: expect roughly a 20 percent reduction in exposure to CYP3A4 substrates.
-
P-glycoprotein: no meaningful effect. Continuous glycyrrhizin did not alter the pharmacokinetics of the P-gp probe substrate talinolol in healthy volunteers.
-
Other CYPs: licorice species and individual constituents inhibit several CYPs in vitro, but the in vitro panel does not predict the in vivo human result, which for CYP3A came out as induction, not inhibition. Do not extrapolate from the in vitro papers.
-
Electrolyte-mediated pharmacodynamic interactions (not CYP, and more important): digoxin (hypokalaemia potentiates digoxin toxicity), loop and thiazide diuretics (additive potassium loss), corticosteroids (glycyrrhetinic acid blocks cortisol inactivation, amplifying steroid effect), antihypertensives (opposed), warfarin, and MAO inhibitors.
Effect of glycyrrhizin on the activity of CYP3A enzyme in humans (2010), PubMed record (2010), Lack of effect of continuous glycyrrhizin administration on the pharmacokinetics of the P-glycoprotein substrate talinolol in healthy volunteers (2012), Cytochrome P450 inhibition by three licorice species and fourteen licorice constituents (2018), Licorice, Merck Manual (drug interactions)
2. Biomarker Verification: what actually verifies target engagement
Separate three questions: is the compound in you, is it hitting the target the paper claims, and is it hitting the target it is actually known to hit.
Tier 1, validated, confirms the known pharmacology (use these):
-
Urinary or salivary cortisol to cortisone ratio. This is the definitive target-engagement marker for glycyrrhetinic acid, because 11-beta-HSD2 inhibition is the one human pharmacodynamic effect that is beyond dispute. A rising ratio means the drug is systemically active. It is also, awkwardly, the marker of the adverse mechanism.
-
Serum potassium. Falls with exposure. Cheap, universal, and the most actionable single number.
-
Plasma renin activity and serum aldosterone. Both suppressed. The signature of pseudoaldosteronism is low renin, low aldosterone, elevated cortisol to cortisone ratio, and rising blood pressure. If you see that pattern you have confirmed engagement and you should stop.
-
Home blood pressure, measured properly over 7 days. Detects the 5 mmHg-scale effect that a single clinic reading will not.
-
ALT and AST. The only human-validated efficacy readout for this compound, and only in people who have elevated transaminases to begin with.