The short answer
It is not established that Gan cao raises methylprednisolone absorption or blood levels. Licorice-related metabolism findings differ by constituent, product and steroid, while BP and potassium precautions may still matter.
What this answer covers
Oral methylprednisolone with Radix et Rhizoma Glycyrrhizae products such as Gan cao. Species, processing, plant part and glycyrrhizin content require verification.
- Supplement or preparation
- Radix et Rhizoma Glycyrrhizae
- Medication ingredient
- methylprednisolone
Which treatment this applies to
This review concerns oral methylprednisolone tablets such as MEDROL. A brief course and prolonged systemic therapy have different clinical contexts. It does not establish the same interactions for injections, depot esters or skin preparations.
A frequently cited study used another steroid
Oral glycyrrhizin increased exposure to intravenously administered prednisolone in six healthy men. The drug was not methylprednisolone, and the supplement was a defined constituent rather than a Gan cao formula. The result does not establish increased oral methylprednisolone absorption.
Other human metabolism results differ
Repeated glycyrrhizin reduced midazolam exposure in one study, indicating induction rather than inhibition. A separate authenticated G.glabra extract depleted in glycyrrhizic acid did not significantly change the exposure of four probe medicines. These findings make blanket predictions from the word licorice unreliable.
Review the actual product and clinical risk
Bring the species, root/rhizome preparation, processing details and other ingredients. The European assessment cautions that licorice does not inhibit every corticosteroid in the same way and retains BP/potassium concerns. Do not increase or reduce methylprednisolone, or add potassium, based on an assumed blood-level interaction.
Evidence and practical considerations
Absorption & effectiveness
Evidence from prednisolone and CYP probe medicines cannot establish increased methylprednisolone exposure with an unspecified Gan cao preparation.
- Exact scope
- Oral methylprednisolone with Radix et Rhizoma Glycyrrhizae products such as Gan cao. Species, processing, plant part and glycyrrhizin content require verification. with Exact RxNorm 6902 IN methylprednisolone; MEDROL plain oral tablets. Injectable esters, depot formulations and topical products are not assumed equivalent.
- Medication form and route
- Oral
What remains uncertain
- No exact Gan cao-methylprednisolone trial. IV prednisolone, isolated constituents and glycyrrhizic-acid-depleted G.glabra cannot establish the target preparation’s direction or magnitude.
Factors that may matter: Exact oral preparation and dose; Treatment duration and indication; Blood pressure and electrolyte status; Other medicines.
Read the supporting source summaries
Source 1: Current prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed MEDROL methylprednisolone oral tablets.
Describes immune suppression, osteoporosis and calcium excretion; salt retention and potassium loss are less likely with synthetic derivatives except at large doses. Dietary adjustment or potassium supplementation may be necessary in context.
How this applies: Exact ingredient and specified formulation. Exact RxNorm 6902 IN methylprednisolone; MEDROL plain oral tablets. Injectable esters, depot formulations and topical products are not assumed equivalent.
Label does not prove universal deficiency or direct supplement absorption interactions. Dose, duration and formulation matter.
Source 2: Original clinical research
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Six healthy men.
Prednisolone exposure increased and clearance decreased.
How this applies: Applicable only to the stated preparation, route and endpoints; other-drug evidence is indirect.
Abstract-only; different corticosteroid, IV steroid route and isolated constituent, not oral methylprednisolone with Gan cao. No transfer of effect direction or magnitude.
Source 3: Original clinical research
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Sixteen healthy men in a crossover.
Midazolam AUC fell, supporting modest CYP3A induction rather than inhibition.
How this applies: Applicable only to the stated preparation, route and endpoints; other-drug evidence is indirect.
Abstract-only probe drug, not methylprednisolone. Exact root/rhizome preparation and oral dose cannot be inferred.
Source 4: Original clinical research
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Fourteen healthy menopausal/postmenopausal women.
No significant AUC changes in CYP1A2, CYP2C9, CYP2D6 or CYP3A4/5 probes.
How this applies: Applicable only to the stated preparation, route and endpoints; other-drug evidence is indirect.
Abstract-only; defined depleted extract not Gan cao or every licorice product. FullTextXML404 and PMC challenge page were not treated as body access.
Source 5: Final regulatory assessment
ema.europa.eu · Source check Sep 10, 2026
Population: Users of defined G.glabra, G.inflata or G.uralensis root/stolon preparations.
BP elevation, fluid retention and potassium loss; precaution against corticosteroid co-use that could aggravate electrolyte imbalance. Explicitly rejects assuming inhibition of every corticosteroid and notes dexamethasone counterevidence.
How this applies: Preparation-limited electrolyte/BP precaution; steroid-specific counterevidence retained.
Not an exact methylprednisolone combination incidence or universal PK effect. Deglycyrrhizinated products and processed Gan cao preparations differ.
Source 6: Medication terminology
rxnav.nlm.nih.gov · Source check Sep 10, 2026
Population: Terminology.
methylprednisolone is IN.
How this applies: Exact ingredient.
Not clinical evidence.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Sources checked and article drafted. | |
| Research summary published |
Article revision: 59912b0b61931297
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.