Drug & supplement interaction

Fireweed + Lapatinib

Lapatinib brand name: Tykerb.

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 Fireweed and Lapatinib 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

Fireweed and Lapatinib

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 Lapatinib and Fireweed 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 Fireweed at all — not against Lapatinib, 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.

Fireweed safety at a glance

Fireweed overall Use caution Generally considered low-risk as a tea, but human safety data are limited.
Pregnancy Avoid Not enough safety information, so it is best to avoid it.
Breastfeeding Avoid Safety has not been established, so avoid use while breastfeeding.

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

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

What Lapatinib’s Own FDA Label Lists

This is not an interaction — none of it involves Fireweed. These are the most notable effects listed in the ADVERSE REACTIONS section of Lapatinib’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.

  • Diarrhea mentioned in 27.1% of FDA reports for Lapatinib
  • Acne
  • Mouth irritation or sores
  • Tiredness mentioned in 8.5% of FDA reports for Lapatinib
  • Vomiting mentioned in 7.8% of FDA reports for Lapatinib
  • A skin rash mentioned in 6.9% of FDA reports for Lapatinib
  • Nausea mentioned in 10.5% of FDA reports for Lapatinib

From the ADVERSE REACTIONS section of the FDA label for Lapatinib. Read the label on DailyMed › Where a percentage is shown, it is the share of 15,427 voluntary FDA FAERS reports for Lapatinib that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Fireweed’s licensed record lists no adverse effects our clinical vocabulary could match, so there is no Fireweed side to compare — that is a limit of the record, not a statement that Fireweed has no side effects.

Everything else you take

See Every Supplement That Interacts With Lapatinib

This page covers Fireweed only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Lapatinib page lists 143 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), St. John's Wort (major), Acacia Rigidula (moderate) and Adrafinil (moderate).

By severity: 3 major · 100 moderate · 40 minor.

From our pharmacist’s overview on the Lapatinib page

“Of the 143 supplements on file for lapatinib (Tykerb), nearly all press on the same point, the CYP3A4 enzyme that clears this HER2-targeted breast cancer drug. That deserves real caution, since lapatinib only works when its blood level stays in range.”

Reviewed by 2 · Jul 18, 2026

Open the Lapatinib interaction page

One more smart check

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

We hold 5 real supplement products containing Fireweed, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Fireweed. Even though Fireweed itself has no known interaction with Lapatinib, 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 Fireweed and Lapatinib 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 Fireweed
Steady interest

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

29 days ago today
Medication Lapatinib
Steady interest

#1,543 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 Fireweed reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Fireweed and Lapatinib 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 Fireweed

What is Fireweed?

  • Prostate and urinary symptoms
  • Digestive upset and diarrhea
  • Skin irritation (topical)
  • Sore throat and mouth inflammation
  • General anti-inflammatory support

Fireweed is a wild flowering plant used traditionally as a tea and folk remedy, most often for prostate, urinary, digestive, and skin complaints. Human evidence is very limited, so its benefits are not well proven. Talk with your pharmacist or doctor before using it, and avoid it during pregnancy and breastfeeding.

Epilobium angustifolium · Onagraceae · Aerial parts (leaves, flowers, and stems); a related species, Epilobium parviflorum, is often used for prostate concerns · Tea, dried herb, tincture, capsules, topical preparations

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

Fireweed: dosing

There is no well-established standardized dose for fireweed. Traditional use often involves a tea made from the dried leaves, while supplements come in capsules or tinctures with varying strengths.Because products differ so much, the safest approach is to follow the directions on the product label and not exceed the recommended amount. A pharmacist can help you review a specific product and decide whether it is appropriate for you.If you do not notice benefit, or you have ongoing symptoms, see a healthcare provider instead of increasing the dose on your own.

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

Read the full Fireweed monograph & all interactions
Medication

About Lapatinib

What Is Lapatinib Used For?

Brand name: Tykerb

Lapatinib tablets — sold under the brand name Tykerb — are used to treat advanced or metastatic breast cancer in patients whose tumors overexpress the HER2 protein. They are always used in combination with another medicine, not alone.

Tykerb is approved in combination with capecitabine for HER2-positive advanced or metastatic breast cancer in patients who have already received prior treatment including an anthracycline, a taxane, and trastuzumab, and whose disease has progressed on trastuzumab. Tykerb is also approved in combination with letrozole for postmenopausal women with hormone receptor-positive, HER2-positive metastatic breast cancer when hormonal therapy is appropriate.

Most-Reported Side Effects for Lapatinib

From FAERS, the FDA’s public side-effect reporting system (15,427 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Diarrhea 4,174 reports
Nausea 1,615 reports
Fatigue 1,305 reports
Vomiting 1,209 reports
Rash 1,061 reports
See full Lapatinib drug information
Keep checking

Other Drugs & Fireweed

Browse every other medication we’ve checked against Fireweed — 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 Fireweed 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 Fireweed list.

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

Fireweed References

The 1 references that drive our Fireweed 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. Esposito C, Santarcangelo C, Masselli R, et al. Epilobium angustifolium L. extract with high content in oenothein B on benign prostatic hyperplasia: A monocentric, randomized, double-blind, placebo-controlled clinical trial. Biomed Pharmacother. 2021 Jun; 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 Fireweed and Lapatinib Together: Common Questions

Is it safe to take Fireweed with Lapatinib?
We do not list a known interaction between Fireweed and Lapatinib. 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 Lapatinib interact with any supplements?
Yes. Lapatinib has documented interactions with 143 supplements in our database — Fireweed is not one of them. The Lapatinib 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

Fireweed monograph Uses, safety profile, and every drug interaction in one place Lapatinib drug information The full plain-English guide to this medication Lapatinib supplement interactions Every supplement checked against Lapatinib, 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 Lapatinib and Fireweed?

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.