Drug & supplement interaction

Knotweed + Formoterol

Formoterol brand names: Foradil Aerolizer, Atimos Modulite, Oxis Turbohaler, Perforomist, Foradil Certihaler.

No Known Interaction
Medically reviewed by · Updated June 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Knotweed and Formoterol 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.

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Interaction report

Knotweed and Formoterol

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 Formoterol and Knotweed 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.

Worth understanding: our licensed dataset holds no drug-interaction record for Knotweed at all — not against Formoterol, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.

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.

Knotweed safety at a glance

Knotweed overall Use caution May be reasonably tolerated short-term, but human safety data are limited and it can cause digestive side effects.
Pregnancy Avoid Not enough safety information; some compounds may affect the uterus, so avoid during pregnancy.
Breastfeeding Avoid There is not enough safety information, so avoid use while breastfeeding.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Formoterol and Knotweed? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

What Formoterol’s Own FDA Label Lists

This is not an interaction — none of it involves Knotweed. These are the most notable effects listed in the ADVERSE REACTIONS section of Formoterol’s own FDA label, for the medication by itself. Knowing the drug’s own list makes it easier to work out the likely cause if something new turns up while you take both. 7 of them are worth acting on rather than waiting out — marked below.

  • Low potassium Worth acting on
  • High blood sugar Worth acting on
  • Wheezing Worth acting on
  • Chest pain Worth acting on
  • Raised blood pressure Worth acting on
  • A severe allergic reaction Worth acting on
  • Hives Worth acting on
  • Tremor or shakiness
  • Dry mouth
  • A fast or pounding heartbeat

Showing the 10 most notable of 22 label-listed effects — ranked by how unusual each one is across medicines generally, with serious effects weighted up.

From the ADVERSE REACTIONS section of the FDA label for Formoterol. Read the label on DailyMed › Knotweed’s licensed record lists no adverse effects our clinical vocabulary could match, so there is no Knotweed side to compare — that is a limit of the record, not a statement that Knotweed has no side effects.

Everything else you take

See Every Supplement That Interacts With Formoterol

This page covers Knotweed only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Formoterol page lists 103 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,3-dmaa (moderate), Acacia Rigidula (moderate), Active Hexose Correlated Compound (ahcc) (moderate), Adrafinil (moderate) and African Wild Potato (moderate).

By severity: 84 moderate · 19 minor.

From our pharmacist’s overview on the Formoterol page

“Formoterol (Foradil, Perforomist) is the long-acting half of many asthma and COPD inhalers, keeping airways open for hours, and its supplement list is calmer than its length suggests. None of the 103 ingredients on file is rated major.”

Reviewed by 2 · Jul 18, 2026

Open the Formoterol interaction page

One more smart check

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

We hold 46 real supplement products containing Knotweed, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Knotweed. Even though Knotweed itself has no known interaction with Formoterol, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Knotweed and Formoterol 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 Knotweed
Steady interest

#1,196 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Formoterol
Steady interest

#2,418 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 Knotweed reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Knotweed and Formoterol records this page draws on were last updated June 22, 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 Knotweed

What is Knotweed?

  • Source of resveratrol
  • Heart and circulation support
  • Lyme disease support (traditional/herbalist use)
  • Inflammation
  • Traditional Chinese medicine remedies

Japanese knotweed (Polygonum cuspidatum) is an herb best known as a natural source of resveratrol and emodin, and it is used in traditional Chinese medicine and by some herbalists. Human evidence for most modern health claims is limited, and it can cause digestive upset, so talk with your pharmacist or doctor before using it.

Polygonum cuspidatum · Polygonaceae · Roots and rhizomes (most common); also leaves and stems · Capsules, tablets, powdered root extract, tinctures, teas

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

Knotweed: dosing

There is no official, well-established dose for knotweed. The right amount depends on the product, how it is prepared, and how much resveratrol or other active compound it contains.Because extracts vary widely in strength, the safest approach is to follow the directions on the product label and not exceed them. A pharmacist or doctor can help you decide whether knotweed is appropriate for you and what amount may be reasonable. Choose products from reputable companies that test for quality and clearly list the species used.

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

Read the full Knotweed monograph & all interactions
Medication

About Formoterol Oral Inhalation

What Is Formoterol Oral Inhalation Used For?

Brand names: Foradil Aerolizer, Atimos Modulite, Oxis Turbohaler, Perforomist, Foradil Certihaler

Formoterol fumarate inhalation solution is used for the long-term maintenance treatment of airway narrowing (bronchoconstriction) in adults with COPD, including chronic bronchitis and emphysema. It is taken twice daily — morning and evening — as a regular, ongoing treatment.

Important limits: This medication is not for relieving sudden COPD flare-ups or breathlessness in the moment, and it is not approved to treat asthma. A separate short-acting inhaler should always be on hand for sudden symptoms.

See full Formoterol Oral Inhalation drug information
Keep checking

Other Drugs & Knotweed

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

0Major
0Moderate
0Minor
2,829No known interaction
2,829 No interaction
No interaction 2,829 drugs checked — show the list

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

Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Knotweed list.

See the full Knotweed interactions page
See every supplement checked against Formoterol, ranked by severity
Evidence & sources

Knotweed References

The 1 references that drive our Knotweed 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. Gonzalez Begne M, Yslas N, Reyes E, et al. Clinical effect of a Mexican sanguinaria (Polygonum aviculare L.) on gingivitis. J Ethnopharmacol 2001;74:45-51..

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 Knotweed and Formoterol Together: Common Questions

Is it safe to take Knotweed with Formoterol?
We do not list a known interaction between Knotweed and Formoterol. 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.
Does Formoterol interact with any supplements?
Yes. Formoterol has documented interactions with 103 supplements in our database — Knotweed is not one of them. The Formoterol 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

Knotweed monograph Uses, safety profile, and every drug interaction in one place Formoterol Oral Inhalation drug information The full plain-English guide to this medication Formoterol supplement interactions Every supplement checked against Formoterol, 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 1 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Formoterol and Knotweed?

Our pharmacists answer your medication & supplement questions — free.

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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.