Drug & supplement interaction

Yellow Loosestrife + 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 Yellow Loosestrife 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

Yellow Loosestrife 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 Yellow Loosestrife 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 Yellow Loosestrife 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.

Yellow Loosestrife safety at a glance

Yellow Loosestrife overall Not established Human safety data are very limited, so use cautiously and talk to a healthcare provider first.
Pregnancy Avoid Not enough safety information exists, so it is best avoided during pregnancy.
Breastfeeding Avoid Safety while breastfeeding is unknown, so avoid it to be safe.

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

Still wondering about combining Lapatinib and Yellow Loosestrife? 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 Yellow Loosestrife. 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. Yellow Loosestrife’s licensed record lists no adverse effects our clinical vocabulary could match, so there is no Yellow Loosestrife side to compare — that is a limit of the record, not a statement that Yellow Loosestrife has no side effects.

Everything else you take

See Every Supplement That Interacts With Lapatinib

This page covers Yellow Loosestrife 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

How much people look this up

Where Yellow Loosestrife 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 Yellow Loosestrife
Steady interest

#1,444 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Lapatinib
Steady interest

#1,469 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. Yellow Loosestrife is not yet covered by that licensed database, so its write-up cites publicly available medical sources directly (see the references below).
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Yellow Loosestrife reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Yellow Loosestrife 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 Yellow Loosestrife

What is Yellow Loosestrife?

  • Diarrhea and digestive upset
  • Minor wounds and bleeding
  • Mouth and throat irritation
  • Mild gastrointestinal complaints

Yellow loosestrife (Lysimachia vulgaris) is a traditional European herb used mostly for diarrhea, minor bleeding, and mouth or throat irritation. There is very little modern scientific evidence to confirm it works, and its safety has not been well studied, so it should be used cautiously and avoided in pregnancy and breastfeeding.

Lysimachia vulgaris · Primulaceae · Aerial parts (leaves, stems, and flowers) · Tea (infusion), tincture, dried herb, occasionally topical preparations

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

Yellow Loosestrife: dosing

There is no established standard dose for yellow loosestrife. Modern science has not determined a safe or effective amount.If you choose to use a product, follow the directions on the label and do not exceed them.

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

Read the full Yellow Loosestrife 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 & Yellow Loosestrife

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

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

Yellow Loosestrife References

The 2 sources that drive our Yellow Loosestrife monograph — publicly available pages from reputable medical and government organizations. Every link was verified to work before publishing. Yellow Loosestrife is not covered by the licensed Natural Medicines interaction database, so its page cites these public sources directly.

  1. Herbs at a Glance — NIH National Center for Complementary and Integrative Health Source
  2. Herbs and Supplements — MedlinePlus (U.S. National Library of Medicine) Source

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 Yellow Loosestrife and Lapatinib Together: Common Questions

Is it safe to take Yellow Loosestrife with Lapatinib?
We do not list a known interaction between Yellow Loosestrife 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 — Yellow Loosestrife 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

Yellow Loosestrife 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 2 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Lapatinib and Yellow Loosestrife?

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.