Herb & supplement monograph

Hu Zhang Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated June 2026

What is this page for?

First and foremost: how Hu Zhang interacts with medications. The heart of this page is the interaction list — every drug Hu Zhang is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Hu Zhang is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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On this page

Hu Zhang Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Hu Zhang drug interaction appears low for most people. None of the listed interactions are rated major, and nearly all rest on lab or animal findings rather than effects confirmed in people.

Interactions deserving the most attention

The combination we watch most closely is Hu Zhang with anticoagulant or antiplatelet drugs, because its resveratrol content may add a mild blood-thinning effect, and even a theoretical bleeding risk matters with these closely monitored medicines. One small human study also found that resveratrol raised levels of a muscle relaxant cleared by a particular liver enzyme, so a modest effect on some medications is plausible. Animal research suggests Hu Zhang could raise levels of the seizure medicine carbamazepine, though this has not been seen in humans.

What the rest of the list means

The long list of interacting medications looks daunting, but it mostly reflects one theory repeated many times: resveratrol might slow enzymes the body uses to clear many drugs. Almost all of these predictions come from lab studies, and in one human trial a predicted effect on a major drug-clearing enzyme did not lead to any meaningful changes in people's medications.

Check your medications against Hu Zhang

Based on HelloPharmacist’s Hu Zhang interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Hu Zhang

828 medications have a known interaction with Hu Zhang, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Hu Zhang using our pharmacist-reviewed interaction data.

AI summaries are generated from our Hu Zhang interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Hu Zhang combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Hu Zhang affects

Every type of medication (drug category) Hu Zhang is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 7 drug categories Hu Zhang interacts with

Anticoagulant/antiplatelet DrugsCytochrome P450 1a2 (cyp1a2) SubstratesCytochrome P450 2c19 (cyp2c19) SubstratesCytochrome P450 2e1 (cyp2e1) SubstratesCytochrome P450 3a4 (cyp3a4) SubstratesEstrogensCarbamazepine (tegretol)

Anticoagulant/Antiplatelet Drugs

Theoretically, hu zhang might increase the risk of bleeding when taken with anticoagulant or antiplatelet drugs.
Hu zhang contains the constituent resveratrol. Resveratrol seems to have antiplatelet effects.

Likelihood Possible Evidence D

Cytochrome P450 1A2 (Cyp1A2) Substrates

Theoretically, hu zhang might increase levels of drugs metabolized by CYP1A2.
Hu zhang contains the constituent resveratrol. In vitro research shows that resveratrol might inhibit the CYP1A2 enzyme. This interaction has not been reported in humans.

Likelihood Possible Evidence D

Cytochrome P450 2C19 (Cyp2C19) Substrates

Theoretically, hu zhang might increase levels of drugs metabolized by CYP2C19.
Hu zhang contains the constituent resveratrol. In vitro research shows that resveratrol might inhibit the CYP2C19 enzyme. This interaction has not been reported in humans.

Likelihood Possible Evidence D

Cytochrome P450 2E1 (Cyp2E1) Substrates

Theoretically, hu zhang might increase levels of drugs metabolized by CYP2E1.
Hu zhang contains the constituent resveratrol. In vitro research shows that resveratrol might inhibit the CYP2E1 enzyme. Also, a pharmacokinetic study shows that taking resveratrol 500 mg daily for 10 days prior to taking a single dose of chlorzoxazone 250 mg increases the maximum concentration of chlorzoxazone by about 54%, the area under the curve of chlorzoxazone by about 72%, and the half-life of chlorzoxazone by about 35%. Chlorzoxazone is used as a probe drug for CYP2E1.

Likelihood Possible Evidence D

Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, hu zhang might increase levels of drugs metabolized by CYP3A4.
Hu zhang contains the constituent resveratrol. In vitro research shows that resveratrol might inhibit the CYP3A4 enzyme. However, a clinical study in adults with NAFLD found that adding resveratrol 3000 mg daily for 8 weeks did not necessitate dose adjustments to any established medications metabolized by CYP3A4.

Likelihood Possible Evidence D

Estrogens

Theoretically, hu zhang might competitively inhibit the effects of estrogen replacement therapy.
In vitro research shows that hu zhang might have estrogenic activity.

Likelihood Possible Evidence D

Carbamazepine (Tegretol)

Theoretically, hu zhang might increase the effects and adverse effects of carbamazepine.
In animals, blood and tissue levels of carbamazepine were increased when given in combination with hu zhang. It is thought that increased levels of carbamazepine are due to cytochrome P450 3A4 (CYP3A4) inhibition. This interaction has not been reported in humans.

Likelihood Possible Evidence D

Monograph

Hu Zhang: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed June 2026 ·

The bottom line

Hu Zhang (Japanese knotweed root) is a traditional Chinese herb that is one of the richest natural sources of resveratrol and emodin. Some lab and early human research looks interesting for inflammation and heart health, but high-quality evidence in people is limited. Talk to your pharmacist or doctor before using it, and avoid it during pregnancy and breastfeeding.

Scientific name: Reynoutria japonica
Family: Polygonaceae
Part used: Root and rhizome
Common forms: Capsules, tablets, powder, tincture, dried root for tea (decoction), standardized resveratrol extracts

People commonly use it for

Source of resveratrol
Heart and circulation support
Inflammation
Liver and digestive complaints (traditional)
Cough and respiratory symptoms (traditional)
Skin and joint conditions (traditional topical use)

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Generally used in traditional medicine, but human safety data for supplements are limited and its emodin content may cause digestive upset.

PregnancyInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Hu Zhang is the dried root and rhizome of Reynoutria japonica, the plant also known as Japanese knotweed. It is native to East Asia and has been used for a long time in traditional Chinese medicine. The plant now grows widely around the world and is often considered an invasive weed in Europe and North America.

In traditional practice, Hu Zhang has been used for problems with the joints, skin, liver, lungs, and digestion. Today it is best known in the supplement world as one of the most concentrated natural sources of resveratrol, the same compound found in grapes and red wine. Many resveratrol products on the market are actually made from Hu Zhang root.

It is sold as capsules, powders, tinctures, and as a dried root used to make tea. It may be used alone or combined with other herbs.

How it works

Hu Zhang contains several active compounds. The two most studied are resveratrol and a group of substances called emodin and other anthraquinones. It also contains polyphenols and a related compound called polydatin (a form of resveratrol).

In laboratory and animal studies, resveratrol acts as an antioxidant and may affect pathways involved in inflammation, blood vessel function, and cell signaling. Emodin has shown anti-inflammatory and possible antimicrobial effects in the lab, but it can also act as a natural laxative.

It is important to understand that most of these mechanisms come from test-tube and animal research. How well they apply to people taking the herb by mouth is still unclear, partly because resveratrol is not absorbed very well by the body.

Effectiveness

Does Hu Zhang work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 11 uses evaluated

11 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

For Hu Zhang, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 11 conditions — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Allergic rhinitis (hay fever)