Drug & supplement interaction

Foxglove + Guanethidine, Hydrochlorothiazide

Guanethidine, Hydrochlorothiazide brand name: Esimil.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Foxglove has a moderate interaction with Guanethidine, Hydrochlorothiazide. Theoretically, concomitant use of potassium depleting diuretics increases the risk of cardiac glycoside toxicity.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Foxglove and Guanethidine, Hydrochlorothiazide

Here is the interaction we found between these two, with the evidence behind it.

Moderate

DIURETIC DRUGS

Why this applies to Guanethidine, Hydrochlorothiazide

Guanethidine, Hydrochlorothiazide falls under DIURETIC DRUGS — the group Foxglove interacts with.

Theoretically, concomitant use of potassium depleting diuretics increases the risk of cardiac glycoside toxicity.
Foxglove contains varied cardiac glycosides, including digoxin. Hypokalemia increases the risk of cardiac glycoside toxicity.
Severity Moderate Likelihood Possible Evidence D

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.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

First, the big picture: foxglove should never be taken on its own. It contains the same kind of heart chemicals (cardiac glycosides) found in the prescription drug digoxin, and even small amounts can be dangerous. Your medicine Esimil contains hydrochlorothiazide, a water pill that can lower your body's potassium level over time.

Here's where they collide. When potassium runs low, the heart becomes much more sensitive to those foxglove glycosides, raising the risk of toxicity: nausea, vision changes, dizziness, and dangerous irregular heartbeats. This concern is based on pharmacology rather than firm studies, but the stakes are simply too high to gamble with. Please don't use foxglove, and check in with your pharmacist or doctor about any supplements.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
  2. Burnham TH, ed. Drug Facts and Comparisons, Updated Monthly. Facts and Comparisons, St. Louis, MO.

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction 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.
  • PossibleInteraction 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.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Foxglove Also Interacts With Other Medications

Foxglove has 3 major, 129 moderate known drug interactions in our database — the Guanethidine, Hydrochlorothiazide one above is one of them. If you take anything else, check it against the full list below.

Major 3 Moderate 129 No known interaction 2,698 (incl. Guanethidine, Hydrochlorothiazide)
Taking anything else?

Check Another of Your Medications Against Foxglove

Covers the 2,830 medications we’ve checked against Foxglove. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Guanethidine, Hydrochlorothiazide

This page covers Foxglove only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Guanethidine, Hydrochlorothiazide page lists 231 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), American Mistletoe (major), Asarabacca (major) and Dolomite (major).

By severity: 10 major · 196 moderate · 25 minor.

From our pharmacist’s overview on the Guanethidine, Hydrochlorothiazide page

“Guanethidine with hydrochlorothiazide (Esimil) lowers blood pressure two ways at once, and 231 supplement and herbal ingredients on file can interfere with it, ten rated major and just 25 minor, so treat this page with genuine care. Most of the 196 moderate entries pile extra blood-pressure-lowering on top of the drug, and a second lar…”

Reviewed by 2 · Jul 18, 2026

Open the Guanethidine, Hydrochlorothiazide interaction page

One more smart check

Taking Foxglove as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1 real supplement products containing Foxglove, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Foxglove. Your product may carry other ingredients that interact with Guanethidine, Hydrochlorothiazide too, on top of Foxglove — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Foxglove and Guanethidine, Hydrochlorothiazide Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Foxglove
Steady interest

#747 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Guanethidine, Hydrochlorothiazide
Steady interest

#1,603 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Foxglove

What is Foxglove?

  • Heart failure (historical/medical use)
  • Irregular heartbeat (historical/medical use)
  • Fluid retention or 'dropsy' (historical use)
  • Ornamental garden plant

Foxglove is a beautiful but highly poisonous plant that contains powerful heart-affecting compounds called cardiac glycosides. It should never be used as a home remedy or supplement because even small amounts can cause life-threatening heart problems. The purified prescription drugs derived from it (like digoxin) are used only under close medical supervision.

Read the full Foxglove monograph & all interactions
Keep checking

Other Drugs & Foxglove

Browse every other medication we’ve checked against Foxglove — both the ones with a known interaction and the ones without. Select any drug for the full detail.

3Major
129Moderate
0Minor
2,697No known interaction
3 Major 129 Moderate 2,697 No interaction
Major

3 interactions

Moderate

129 interactions

Showing 60 of 129 moderate interactions — see all 129 on the Foxglove page.

No interaction 2,697 drugs checked — show the list

We also checked Foxglove against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,697 medications checked with no known interaction — see the full Foxglove list.

See the full Foxglove interactions page
See every supplement checked against Guanethidine, Hydrochlorothiazide, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

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

Keep exploring
Foxglove monograph › Uses, safety, and every drug interaction in one place Guanethidine, Hydrochlorothiazide supplement interactions › Every supplement checked against Guanethidine, Hydrochlorothiazide, ranked by severity Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Foxglove and Guanethidine, Hydrochlorothiazide Together: Common Questions

Can you take Foxglove with Guanethidine, Hydrochlorothiazide?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Foxglove and Guanethidine, Hydrochlorothiazide interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Guanethidine, Hydrochlorothiazide and Foxglove?

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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.