Herb & supplement monograph

White Horehound Drug Interactions, Uses, Effectiveness, Safety & More

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

What is this page for?

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

But these pages have grown well beyond that into a full monograph — what White Horehound 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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White Horehound 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 White Horehound drug interaction appears low for most people. None of the listed interactions are rated major, and all are moderate concerns based on theoretical or early-stage evidence rather than proven effects in people.

Interactions deserving the most attention

The combinations worth watching involve diabetes medications and blood pressure medications. Animal research suggests white horehound may lower blood sugar, though early human research found only a slight added effect alongside diabetes drugs, which may not matter clinically for most people. The blood pressure concern comes from animal studies only, where the herb lowered blood pressure, so pairing it with drugs like losartan or amlodipine could in theory drop pressure too far. Because blood sugar and blood pressure are closely monitored numbers, a small shift is easier to catch than to predict.

What the rest of the list means

The long list of interacting medications reflects how many drugs fall into these two broad categories, not hundreds of separate proven problems. Almost all of these pairings are theoretical, predicted from animal or lab findings, and the best human data so far suggests the real-world effect is modest at most.

Check your medications against White Horehound

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

Interaction report

Drugs that interact with White Horehound

258 medications have a known interaction with White Horehound, 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 White Horehound using our pharmacist-reviewed interaction data.

AI summaries are generated from our White Horehound 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 White Horehound 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 White Horehound affects

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

All 2 drug categories White Horehound interacts with

Antidiabetes DrugsAntihypertensive Drugs

Antidiabetes Drugs

Evidence from animal research suggests that white horehound might lower blood glucose. However, preliminary clinical research suggests that white horehound only slightly lowers blood glucose when taken in combination with antidiabetic agents, suggesting that the effect may not be clinically significant. Until more is known, use with caution. Theoretically, white horehound may have additive effects when used by patients taking antidiabetic drugs. The dose of diabetes medications might need to be adjusted. Some antidiabetes drugs include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, metformin (Glucophage), pioglitazone (Actos), rosiglitazone (Avandia), and others.

Likelihood Possible Evidence B

Antihypertensive Drugs

Evidence from animal research suggests that taking white horehound extract lowers blood pressure. Theoretically, taking white horehound with antihypertensive drugs might enhance therapeutic effects and increase the risk of hypotension. Some antihypertensive drugs include captopril (Capoten), enalapril (Vasotec), losartan (Cozaar), valsartan (Diovan), diltiazem (Cardizem), Amlodipine (Norvasc), hydrochlorothiazide (HydroDiuril), furosemide (Lasix), and many others.

Likelihood Possible Evidence D

Monograph

White Horehound: Uses, Safety & Side Effects

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

The bottom line

White horehound is a traditional bitter herb used mainly for coughs, sore throats, and mild digestive complaints, and it is a common flavoring in old-fashioned cough drops. Solid human evidence supporting these uses is limited, so view it as a folk remedy rather than a proven treatment. Talk to your pharmacist or doctor before using it, and avoid it during pregnancy.

Scientific name: Marrubium vulgare
Family: Lamiaceae
Part used: Leaves and flowering tops (aerial parts)
Common forms: Tea, lozenges, cough syrups, tinctures, capsules, hard candies

People commonly use it for

Cough and chest congestion
Sore throat
Bronchitis
Digestive upset and poor appetite
Bloating and gas

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

Safety at a glance

OverallUse caution

Likely fine in small amounts found in foods and lozenges, but high doses are not well studied.

PregnancyLikely Unsafe

When used orally; white horehound might have abortifacient effect, or stimulate menstrual flow and the uterus. There is insufficient reliable informat...

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

There is insufficient reliable information available about the safety of oral use during lactation; avoid amounts greater than those commonly found in...

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

White horehound (Marrubium vulgare) is a perennial herb in the mint family. It is native to Europe, North Africa, and parts of Asia, and now grows in many parts of the world, often along roadsides and in dry, open areas. The plant has gray-green, wrinkled leaves and small white flowers.

People have used the leaves and flowering tops in herbal medicine for hundreds of years. The herb has a very bitter taste, which is part of why it was traditionally used for coughs and for digestion. Today you may find it in herbal teas, tinctures, and as a flavoring in old-fashioned horehound cough drops and candies.

How it works

White horehound contains a bitter compound called marrubiin, which is considered one of its main active ingredients. It also contains other plant chemicals such as flavonoids, diterpenes, and volatile oils.

The bitter taste is thought to trigger the body to make more saliva and digestive juices, which is the proposed reason for its traditional use in digestion and appetite. For coughs, the herb is believed to thin mucus and soothe the throat. Lab and animal studies have also looked at possible antioxidant, anti-inflammatory, and blood-sugar-lowering actions. Keep in mind that most of these mechanisms come from test-tube or animal research and may not apply the same way in humans.

Effectiveness

Does White Horehound work?

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

Evidence overview · 1 use evaluated

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

Also studied for 1 condition — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Diabetes

Rating & evidence shown verbatim from Natural Medicines

There is preliminary clinical evidence that taking a tea prepared from white horehound three times daily before meals for 21 days, in addition to conventional medicines for type 2 diabetes, slightly reduces fasting blood glucose by about 0.64% compared with baseline. However, the reduction in blood glucose following treatment with white horehound was significantly less than the blood glucose reduction observed for patients who drank tea prepared from guarumo (Cecropia obtusifolia). It is not clear whether white horehound has a clinically significant effect when taken alone.

Sources Ref 86369

Source & disclaimer. Effectiveness ratings and evidence summaries are provided by Natural Medicines (Therapeutic Research Center) and shown as licensed. Where Natural Medicines hasn’t rated a use, HelloPharmacist’s pharmacists may add their own reviewed rating and evidence (each such entry is labeled). This is educational information, not medical advice — talk with your pharmacist or doctor before starting, stopping, or changing a supplement.

Safety & precautions

Small amounts of white horehound, such as those found in cough drops or teas, are generally considered well tolerated by most adults. However, the safety of large amounts or long-term use has not been well studied.

Pregnancy: Avoid white horehound. It has traditionally been thought to stimulate the uterus and could pose a risk during pregnancy. Breastfeeding: There is not enough reliable safety information, so it is best to avoid it. People with diabetes should be cautious, since the herb may affect blood sugar. People with heart rhythm problems, stomach or intestinal ulcers, or any chronic condition should check with a healthcare provider first. Always talk to your pharmacist or doctor before starting any herbal supplement.

Side effects

White horehound is usually well tolerated in the small amounts found in foods and lozenges. When taken in larger doses, it may cause nausea, vomiting, or stomach upset because of its bitterness and possible irritation of the digestive tract.

Some sources note that very large amounts could affect heart rhythm or blood pressure, so high doses are not recommended. Allergic reactions are possible, especially in people sensitive to plants in the mint family. Stop using it and seek medical care if you have signs of an allergic reaction such as rash, swelling, or trouble breathing.

White Horehound: Reported Adverse Effects

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

Orally, white horehound may cause nausea, dry mouth, excessive salivation, loss of appetite, and dizziness in some patients. Large amounts of white horehound (exact dose is unclear) may cause purgative effects.

Topically, skin contact with the plant juice may cause contact dermatitis.

Herrera-Arellano, A., Aguilar-Santamaria, L., Garcia-Hernandez, B., Nicasio-Torres, P., and Tortoriello, J. Clinical trial of Cecropia obtusifolia and Marrubium vulgare leaf extracts on blood glucose and serum lipids in type 2 diabetics. Phytomedicine 200
Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.

Reports by condition

Dermatitis Dermatologic

Topically, skin contact with the plant juice may cause contact dermatitis.

Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.

Dry mouth Gastrointestinal

Orally, clinical research shows that drinking one cup of tea prepared with white horehound 1 gram three times daily for 3 weeks may cause nausea, dry mouth, excessive salivation, and loss of appetite in some patients. Intake of large amounts of white horehound (exact dose is unclear) may cause purgative effects.

Herrera-Arellano, A., Aguilar-Santamaria, L., Garcia-Hernandez, B., Nicasio-Torres, P., and Tortoriello, J. Clinical trial of Cecropia obtusifolia and Marrubium vulgare leaf extracts on blood glucose and serum lipids in type 2 diabetics. Phytomedicine 200
Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.

Vertigo Neurologic/CNS

Orally, clinical research shows that drinking one cup of tea prepared with white horehound 1 gram three times daily for 3 weeks may cause dizziness in some patients.

Herrera-Arellano, A., Aguilar-Santamaria, L., Garcia-Hernandez, B., Nicasio-Torres, P., and Tortoriello, J. Clinical trial of Cecropia obtusifolia and Marrubium vulgare leaf extracts on blood glucose and serum lipids in type 2 diabetics. Phytomedicine 200

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 standardized dose for white horehound. The right amount depends on the form, such as tea, tincture, lozenge, or capsule, and the strength of the specific product.

The safest approach is to follow the directions on the product label and not exceed the recommended amount. Because doses vary widely and reliable human data is limited, it is wise to check with your pharmacist or doctor before using it, especially if you have health conditions or take other medicines.

Pregnancy & Breastfeeding

White Horehound & Pregnancy

Likely Unsafe

When used orally; white horehound might have abortifacient effect, or stimulate menstrual flow and the uterus. There is insufficient reliable information available about the safety of topical use during pregnancy; avoid using.

Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.

White Horehound & Breastfeeding

Insufficient reliable information

There is insufficient reliable information available about the safety of oral use during lactation; avoid amounts greater than those commonly found in foods. There is insufficient reliable information available about the safety of topical use during lactation; avoid using.

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 8 references that drive our White Horehound 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.

Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
Roman, Ramos R., Alarcon-Aguilar, F., Lara-Lemus, A., and Flores-Saenz, J. L. Hypoglycemic effect of plants used in Mexico as antidiabetics. Arch.Med.Res 1992;23:59-64.
Novaes AP, Rossi C, Poffo C, et al. Preliminary evaluation of the hypoglycemic effect of some Brazilian medicinal plants. Therapie. 2001;56(4):427-30.
El Bardai, S., Lyoussi, B., Wibo, M., and Morel, N. Pharmacological evidence of hypotensive activity of Marrubium vulgare and Foeniculum vulgare in spontaneously hypertensive rat. Clin Exp Hypertens. 2001;23(4):329-343.
El Bardai, S., Lyoussi, B., Wibo, M., and Morel, N. Comparative study of the antihypertensive activity of Marrubium vulgare and of the dihydropyridine calcium antagonist amlodipine in spontaneously hypertensive rat. Clin Exp Hypertens. 2004;26(6):465-474 PubMed
Herrera-Arellano, A., Aguilar-Santamaria, L., Garcia-Hernandez, B., Nicasio-Torres, P., and Tortoriello, J. Clinical trial of Cecropia obtusifolia and Marrubium vulgare leaf extracts on blood glucose and serum lipids in type 2 diabetics. Phytomedicine 200 PubMed

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.

Pharmacist Counseling Corner

White Horehound: Common Questions

What is White Horehound used for, and does it work?

People use White Horehound for a range of reasons, but according to the Natural Medicines database the current clinical evidence is insufficient to confirm it works for the specific conditions it has been studied for. See the graded list on this page, and talk to your pharmacist or doctor before relying on it for any condition.

Does White Horehound interact with prescription medications?

Yes. We list 258 medications with a known interaction with White Horehound. Use the checker above to see how White Horehound interacts with a specific drug.

How are White Horehound 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 White Horehound 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 White Horehound 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 White Horehound used for?

It is most commonly used as a traditional remedy for coughs, sore throats, and chest congestion, and for mild digestive problems like poor appetite and bloating. Strong human evidence for these uses is limited.

Is White Horehound safe?

Small amounts, such as in cough drops and teas, are generally well tolerated by most adults. Large or long-term doses are not well studied and may cause stomach upset, so it is best to use it cautiously and check with a healthcare provider.

Can I use White Horehound during pregnancy or breastfeeding?

No. It is traditionally believed to stimulate the uterus, so it should be avoided during pregnancy, and there is not enough safety information to recommend it while breastfeeding.

Why does White Horehound taste so bitter?

It contains a bitter compound called marrubiin and other plant chemicals. This bitterness is thought to be part of why it has traditionally been used to support digestion and appetite.

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

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