Herb & supplement monograph

Smartweed Drug Interactions, Uses, Safety & More

Medically reviewed by ·Updated July 2026
What is this page for?

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

But these pages have grown well beyond that into a full monograph — what Smartweed 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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Smartweed 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 Smartweed drug interaction appears low for most people, though anyone taking a blood thinner should pay attention. Only a couple of medications are flagged, none rated major, and the sole concern rests on limited, theoretical evidence.

Interactions deserving the most attention

The one interaction worth knowing about involves warfarin (Coumadin). Smartweed naturally contains vitamin K, and warfarin works by blocking vitamin K, so taking the two together could, in theory, make warfarin less effective. Warfarin is a narrow-margin medicine where even small changes in effect can raise the risk of clots, so this pairing deserves respect even though the interaction has not been confirmed in human studies.

What the rest of the list means

Unlike many supplements, Smartweed has a very short interaction profile, which is genuinely reassuring for most people. Keep in mind that the warfarin concern is based on what Smartweed contains rather than on documented problems in people, so it is a sensible precaution rather than a proven effect.

Check your medications against Smartweed

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

Interaction report

Drugs that interact with Smartweed

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

2,830 drugs
WarfarinWarfarin› Warfarin SodiumCoumadin, Panwarfin, Sofarin› "phentolamineOraVerse, Rogitine, Ryzumvi› 6-mercaptopurinePurinethol› Ado-trastuzumab EmtansineKadcyla› AbacavirZiagen› Abacavir Sulfate, Dolutegravir, LamivudineTriumeq› Abacavir, LamivudineEpzicom› AbaloparatideTymlos› AbametapirXeglyze› AbarelixPlenaxis› AbciximabReoPro› AbemaciclibVerzenio› Abiraterone› Abiraterone AcetateYonsa, Zytiga› AbrocitinibCibinqo› AcalabrutinibCalquence› AcamprosateCampral› AcarboseGlucobay, Prandase, Precose› AcebutololRhotral, Sectral› AcenocoumarolSintrom› AcepromazineAtravet› AcetaminophenChildren's Tylenol, Children's Tylenol Meltaways, Tylenol, Tylenol Ex Strength› Acetaminophen, AspirinGemnisyn› Acetaminophen, Aspirin, CaffeineExcedrin, Excedrin Extra Strength, Excedrin Migraine› Acetaminophen, Brompheniramine, PhenylpropanolamineDimetapp Cold and Flu› Acetaminophen, ButalbitalAxocet, Bancap, Bucet, Butex Forte, Esgic CF, Orbivan CF +5 more› Acetaminophen, Butalbital, CaffeineEsgic, Esgic Plus, Fiogesic, Fioricet, Repan, Tecnal +1 more› Acetaminophen, Butalbital, Caffeine, CodeineEsgic with Codeine, Fioricet w/ Codeine› Acetaminophen, Butalbital, CodeineBancap w/ Codeine›
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 Smartweed 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 Smartweed affects

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

All 1 drug category Smartweed interacts with
Warfarin (coumadin)
Warfarin (Coumadin)

Smartweed contains vitamin K. Concomitant use of smartweed might decrease the anticoagulant effects of warfarin, a vitamin K antagonist.

Likelihood Possible Evidence D
Monograph

Smartweed: Uses, Safety & Side Effects

Medically reviewed by · Reviewed July 2026 ·
The bottom line

Smartweed (Persicaria hydropiper) is a peppery wetland plant with a long history in traditional medicine for digestive complaints, bleeding, and skin problems. Modern human studies are very limited, so its benefits are not well proven. Because safety data are thin, it's best to use cautiously and avoid it during pregnancy and breastfeeding.

Smartweed
Scientific name
Persicaria hydropiper
Family
Polygonaceae
Part used
Aerial parts (leaves, stems, and flowering tops); sometimes the whole plant
Common forms
Tea, tincture, liquid extract, dried herb, and topical preparations
People commonly use it for
  • Digestive upset
  • Minor skin irritation
  • Heavy menstrual bleeding (traditional)
  • Wound and bleeding (traditional topical use)
  • Antioxidant and anti-inflammatory support

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

Safety at a glance
OverallUse caution

There is little modern safety data, so use cautiously and talk to a healthcare provider first.

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

Smartweed is a flowering plant in the buckwheat family. Its leaves have a sharp, peppery taste, which is why it is also called water pepper or marshpepper. It grows in wet places like ditches, stream banks, and marshes across North America, Europe, and parts of Asia.

People have used smartweed in traditional medicine for a long time. It has been taken as a tea or tincture for stomach and digestive problems, and it has been applied to the skin for minor irritation, bleeding, and wounds. In some traditions it was also used to help with menstrual bleeding.

Today it is sold mostly as a dried herb, tea, tincture, or liquid extract. It is not a mainstream supplement, and you will not find it in most pharmacies.

Uses & effectiveness

Smartweed is used traditionally for several purposes, but the scientific evidence is weak. Most research comes from laboratory and animal studies rather than well-designed human trials.

Digestive complaints: It has been used as a tea for stomach upset and diarrhea. There is no strong human evidence to confirm it works for these problems.

Bleeding and menstruation: Traditionally it was used to slow bleeding, including heavy menstrual bleeding, and applied to wounds. Good clinical studies in people are lacking.

Skin irritation: It has been used on the skin for minor irritation and inflammation. Evidence here is also limited and mostly traditional.

Antioxidant and anti-inflammatory effects: Lab studies show the plant contains compounds with antioxidant and anti-inflammatory activity, but this does not prove it helps any specific condition in people.

Overall, the evidence for smartweed is preliminary. It should not be used in place of proven treatments.

How it works

Smartweed contains several natural compounds that may explain its traditional uses. These include flavonoids (such as quercetin and rutin), phenolic acids, tannins, and other plant chemicals. Some types also contain a pungent compound that gives the plant its peppery bite.

In laboratory and animal research, these compounds have shown antioxidant, anti-inflammatory, and antimicrobial activity. Tannins may have an astringent (drying and tightening) effect, which could explain its traditional use for bleeding and diarrhea.

It is important to know that these mechanisms come mostly from test-tube and animal studies. They do not prove that smartweed produces the same effects in the human body at amounts people would actually take.

Safety & precautions

There is not much modern safety information about smartweed, so it should be used cautiously. People with known allergies to plants in the buckwheat family should avoid it.

Pregnancy: Avoid smartweed during pregnancy. It has been used traditionally to affect menstruation and the uterus, which raises a real concern during pregnancy.

Breastfeeding: Avoid it while breastfeeding because there is not enough information to know whether it is safe for the baby.

People with chronic health conditions, those taking prescription medicines, children, and older adults should check with a doctor or pharmacist before using smartweed. Because supplements are not tightly regulated, product quality and strength can vary.

Side effects

Detailed side effect information for smartweed is limited. The plant has a strong peppery taste and may irritate the mouth, throat, or stomach in some people.

When applied to the skin, it may cause irritation, redness, or an allergic reaction in sensitive people. Taking large amounts by mouth could cause stomach upset.

If you notice signs of an allergic reaction, such as rash, swelling, or trouble breathing, stop using it and seek medical care right away. Stop use and talk to a healthcare provider if you have any unexpected or bothersome symptoms.

Smartweed: Reported Adverse Effects

Documented safety reports on Smartweed from the evidence-graded Natural Medicines (TRC Healthcare) database, shown word-for-word from the licensed record.

Orally, smartweed can cause gastrointestinal irritation. Topically, smartweed can cause skin irritation.

  1. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  2. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.
DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

Adverse-effects data: Natural Medicines, Therapeutic Research Center

Dosing

There is no well-established or standardized dose for smartweed. Because it has not been carefully studied in people, experts cannot recommend a safe and effective amount.

If you choose to use a product, follow the directions on the label and do not exceed them. Different forms (tea, tincture, extract) have very different strengths.

The safest approach is to talk with a pharmacist or doctor before starting smartweed, especially if you take other medicines or have a health condition.

Pregnancy & Breastfeeding

Smartweed & Pregnancy

Insufficient reliable information

Insufficient reliable information available; avoid using.

Smartweed & Breastfeeding

Insufficient reliable information

Insufficient reliable information available; avoid using.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

© 2026 Therapeutic Research Center

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 2 references that drive our Smartweed monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.
  2. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
Keep reading

This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Brand directory

Brands that make products with Smartweed

2 brands in our database make a supplement containing Smartweed.

Product directory

Supplement products with Smartweed

4 products in our database contain Smartweed. Open any to see its full ingredient list and every drug interaction we check.

Pharmacist Counseling Corner

Smartweed: Common Questions

Does Smartweed interact with prescription medications?
Yes. We list 2 medications with a known interaction with Smartweed. Use the checker above to see how Smartweed interacts with a specific drug.
How are Smartweed interactions rated?
Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.
Is it safe to take Smartweed with my medications?
It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.
Where does this Smartweed interaction information come from?
Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.
What is Smartweed used for?
Traditionally it has been used for digestive upset, bleeding (including heavy periods), and minor skin irritation. However, there is little strong human evidence showing it works for any of these.
Is Smartweed safe to take?
There is not much modern safety data, so it should be used cautiously. Talk to a pharmacist or doctor before using it, especially if you have a health condition or take other medicines.
Can I use Smartweed during pregnancy or while breastfeeding?
No. It is best to avoid Smartweed during pregnancy because it has traditionally been used to affect menstruation and the uterus, and to avoid it while breastfeeding due to a lack of safety information.
Why does Smartweed taste so peppery?
It contains natural pungent compounds in its leaves, which is why it is also called water pepper or marshpepper. This sharp taste is one of the plant's most recognizable features.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Keep exploring

Products that contain Smartweed

A rotating sample of real supplements in our database that list Smartweed — open any to see its full ingredients and every drug interaction we check.

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