Drug & supplement interaction

Groundsel + Methenamine Mandelate

Methenamine Mandelate brand names: Mandelamine, Methimazole.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 27, 2026
The bottom line No known interaction

We found no known interaction between Groundsel and Methenamine Mandelate in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Groundsel and Methenamine Mandelate

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Methenamine Mandelate and Groundsel in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Groundsel safety at a glance

Groundsel overall Avoid Groundsel contains liver-toxic pyrrolizidine alkaloids and is generally considered unsafe to ingest.
Pregnancy Likely Unsafe When used orally. Groundsel products can contain pyrrolizidine alkaloid (PA) constituents, which might be teratogenic and hepatotoxic. There is insufficient rel... Read the full pregnancy detail
Breastfeeding Likely Unsafe When used orally. Hepatotoxic PA constituents in groundsel are excreted in milk. There is insufficient reliable information available about the safety of using... Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Methenamine Mandelate and Groundsel? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Methenamine Mandelate

Interactions in our licensed database are recorded against drug classes, not just single drug names. Methenamine Mandelate is filed under 4 classifications — including antithyroid drugs, antibiotic drugs, hepatotoxic drugs. Groundsel has documented interactions with 1 drug class — the most serious being cytochrome p450 3a4 (cyp3a4) inducers (moderate) — and none of Methenamine Mandelate’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Groundsel Does Interact With Other Medications

Groundsel has 87 moderate known drug interactions in our database — Methenamine Mandelate isn’t one of them. If you take anything else, check it against the full list below.

Moderate 87 No known interaction 2,743 (incl. Methenamine Mandelate)
Taking anything else?

Check Another of Your Medications Against Groundsel

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

What to actually watch for

No Interaction Found — But Data Suggests Groundsel and Methenamine Mandelate May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do. One of them is worth acting on rather than waiting out — marked below.

  • Liver problems Worth acting on Additional detail

    Groundsel

    “Orally, groundsel may cause hepatotoxicity due to its pyrrolizidine alkaloid (PA) constituents. Chronic exposure hepatotoxic PAs is associated with veno-occlusive disease. Subacute veno-occlusive disease causes vague symptoms with persistent liver enlargement. Symptoms of acute veno-occlusive disease include colicky pains in epigastrium, vomiting and diarrhea, and ascites formation within several days.”

    Groundsel · Natural Medicines adverse-effect record, reported in diarrhea.

    4 sources cited
    1. 4021. WHO working group. Pyrrolizidine alkaloids. Environmental Health Criteria, 80. WHO: Geneva, 1988.
    2. 12842. Roeder E. Medicinal plants in Europe containing pyrrolizidine alkaloids. Pharmazie 1995;50:83-98.
    3. 5606. Fox DW, Hart MC, Bergeson PS, et al. Pyrrolizidine (Senecio) intoxication mimicking Reye syndrome. J Pediatr 1978;93:980-2. PubMed
    4. 3484. Klepser TB, Klepser ME. Unsafe and potentially safe herbal therapies. Am J Health Syst Pharm 1999;56:125-38. PubMed

    Methenamine Mandelate

    Listed in the ADVERSE REACTIONS section of the FDA label for Methenamine Mandelate. Read the label on DailyMed ›

  • Vomiting Additional detail

    Groundsel

    Recorded for Groundsel in the same Natural Medicines adverse-effect record shown under Liver problems above.

    Methenamine Mandelate

    Listed in the ADVERSE REACTIONS section of the FDA label for Methenamine Mandelate. Read the label on DailyMed ›

Reported for Groundsel but not commonly for Methenamine Mandelate: raised blood pressure and diarrhea.

Effects for Methenamine Mandelate come from the ADVERSE REACTIONS section of its FDA label; effects for Groundsel come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 7,806 voluntary FDA FAERS reports for Methenamine Mandelate that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Groundsel in Pregnancy & Breastfeeding

Pregnancy Likely Unsafe

When used orally. Groundsel products can contain pyrrolizidine alkaloid (PA) constituents, which might be teratogenic and hepatotoxic. There is insufficient reliable information available about the safety of using groundsel products that do not contain hepatotoxic PAs during pregnancy. However, dietary supplements sold in the US are not required to include the amount of PAs they contain; therefore, all preparations used orally containing groundsel should be considered likely unsafe.

Lactation Likely Unsafe

When used orally. Hepatotoxic PA constituents in groundsel are excreted in milk. There is insufficient reliable information available about the safety of using groundsel products that do not contain hepatotoxic PAs during lactation. However, dietary supplements sold in the US are not required to include the amount of PAs they contain; therefore, all preparations used orally containing groundsel should be considered likely unsafe.

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

Everything else you take

See Every Supplement That Interacts With Methenamine Mandelate

This page covers Groundsel only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Methenamine Mandelate page lists 91 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Siberian Cocklebur (major), Wine (major) and Ascophyllum Nodosum (moderate).

By severity: 4 major · 77 moderate · 10 minor.

From our pharmacist’s overview on the Methenamine Mandelate page

“People take methenamine mandelate (Mandelamine) day after day to keep urinary tract infections at bay, and that long habit is exactly why the 91 supplements on this page deserve genuine vigilance. Four carry a major rating, and most of those point at the liver: Siberian cocklebur has been linked to outright liver failure, and heavy bee…”

Reviewed by 2 · Jul 18, 2026

Open the Methenamine Mandelate interaction page

How much people look this up

Where Groundsel and Methenamine Mandelate 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 Groundsel
Steady interest

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

29 days ago today
Medication Methenamine Mandelate
Top half

#721 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Groundsel reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 27, 2026. The Groundsel and Methenamine Mandelate records this page draws on were last updated July 11, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Groundsel

What is Groundsel?

  • Menstrual complaints
  • Digestive upset
  • Minor wounds (topical)
  • Sore gums or mouth
  • Mild aches

Groundsel is a common weed traditionally used as a folk remedy, but it contains pyrrolizidine alkaloids that can cause serious liver damage. There is no reliable evidence that it works for any condition, and most health authorities consider it unsafe to take internally. We do not recommend using it.

Senecio vulgaris · Asteraceae · Aerial parts (leaves, stems, flowers) · Tea, dried herb, tincture, topical poultice

An interaction check asks whether these two react with each other — it does not ask whether Groundsel is a good idea for someone in your situation. Here is what our Groundsel record says about it on its own.

Groundsel: dosing

There is no established safe dose for groundsel. Because of its toxic pyrrolizidine alkaloids, no standardized, tested dosing exists, and we do not recommend taking it internally.If you come across a product that contains groundsel, do not assume any amount is safe.

From our Groundsel monograph — the full record covers uses, side effects and every documented interaction.

Read the full Groundsel monograph & all interactions
Medication

About Methimazole

What Is Methimazole Used For?

Brand names: Mandelamine, Methimazole

Methimazole tablets treat hyperthyroidism in people with Graves’ disease or toxic multinodular goiter (a enlarged thyroid with overactive lumps). They are used when surgery or radioactive iodine is not a suitable option.

They are also used to ease hyperthyroid symptoms while a person gets ready for thyroidectomy (thyroid removal surgery) or radioactive iodine therapy.

See full Methimazole drug information
Keep checking

Other Drugs & Groundsel

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

0Major
87Moderate
0Minor
2,742No known interaction
87 Moderate 2,742 No interaction
Moderate

87 interactions

Showing 60 of 87 moderate interactions — see all 87 on the Groundsel page.

No interaction 2,742 drugs checked — show the list

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

Showing the 60 most looked-up of 2,742 medications checked with no known interaction — see the full Groundsel list.

See the full Groundsel interactions page
See every supplement checked against Methenamine Mandelate, ranked by severity
Evidence & sources

Groundsel References

The 6 references that drive our Groundsel 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. Klepser TB, Klepser ME. Unsafe and potentially safe herbal therapies. Am J Health Syst Pharm 1999;56:125-38. PubMed
  2. WHO working group. Pyrrolizidine alkaloids. Environmental Health Criteria, 80. WHO: Geneva, 1988.
  3. Fox DW, Hart MC, Bergeson PS, et al. Pyrrolizidine (Senecio) intoxication mimicking Reye syndrome. J Pediatr 1978;93:980-2. PubMed
  4. Chojkier M. Hepatic sinusoidal-obstruction syndrome: toxicity of pyrrolizidine alkaloids. J Hepatol 2003;39:437-46. PubMed
  5. Roeder E. Medicinal plants in Europe containing pyrrolizidine alkaloids. Pharmazie 1995;50:83-98.
  6. Wang YP, Yan J, Fu PP, Chou MW. Human liver microsomal reduction of pyrrolizidine alkaloid N-oxides to form the corresponding carcinogenic parent alkaloid. Toxicol Lett 2005;155:411-20. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Groundsel and Methenamine Mandelate Together: Common Questions

Is it safe to take Groundsel with Methenamine Mandelate?
We do not list a known interaction between Groundsel and Methenamine Mandelate. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Groundsel and Methenamine Mandelate have any of the same side effects?
Yes — our sources link each of them separately to 2 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
How was the Groundsel and Methenamine Mandelate combination checked?
Interactions in our licensed database are recorded against drug classes. Methenamine Mandelate is filed under 4 classifications, and Groundsel has documented interactions with 1 drug class — none of Methenamine Mandelate's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Groundsel interact with any other medications?
Yes. Groundsel has 87 documented drug interactions in our database — Methenamine Mandelate is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Methenamine Mandelate interact with any supplements?
Yes. Methenamine Mandelate has documented interactions with 91 supplements in our database — Groundsel is not one of them. The Methenamine Mandelate interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Groundsel monograph Uses, safety profile, and every drug interaction in one place Methimazole drug information The full plain-English guide to this medication Methenamine Mandelate supplement interactions Every supplement checked against Methenamine Mandelate, 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 References The 6 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Methenamine Mandelate and Groundsel?

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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.