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Western herbalism

Pau d'arcoTabebuia impetiginosa (Handroanthus impetiginosus)

Pau d’arco bark is sold in parasite-cleanse formulas; we could find no human trial of it for the gut, and its lapachol thins the blood in lab work.

Botanical name
Tabebuia impetiginosa (Handroanthus impetiginosus)
Part used
inner bark
Also called
Lapacho, Red lapacho, Taheebo, Ipe roxo
Used in
Western herbalism
Taken for
Antimicrobial use
Sold as
capsules, tea, tincture, powder, decoction

What is meant by pau d'arco

Pau d’arco is the inner bark of trees in the genus Tabebuia, now often reclassified as Handroanthus, of the trumpet-tree family (Bignoniaceae), native to the Amazon basin and other parts of Latin America. The species most often sold is T. impetiginosa, called red lapacho or taheebo; T. avellanedae is a synonym used for the same material in some papers. The traditional preparation is a decoction of the inner bark. Supplements are bark powder in capsules, tea bags, tinctures and extracts, and pau d’arco is one of the ingredients in multi-herb parasite-cleanse formulas.

Two naphthoquinones, lapachol and beta-lapachone, are the compounds most studied. Product quality is a recurring problem: one review of the species notes that the bark on international markets varies in quality and composition, and the Natural Medicines database reports that some Canadian and Brazilian products lacked the active ingredients in the labeled amounts.

In the traditions

Western herbalism

In the Amazonian and wider South American traditions from which the herb comes, the inner bark is prepared as a decoction for fever, malaria, bacterial and fungal infections, syphilis, trypanosomiasis (a blood parasite infection), skin disease and, in the words of one review, stomach and bladder disorders. The Natural Medicines database adds diarrhea and ulcers to the traditional list. Supplement sellers market the bark for cancer, bacterial infections and fungal infections, the purported uses Memorial Sloan Kettering lists. We did not find a source that documents a traditional use against intestinal worms, which is the use the cleanse formulas imply; the traditional antiparasitic entries are for malaria and trypanosomiasis.

What the plant contains

Lapachol and beta-lapachone are the most-studied constituents, with anthraquinones also present. In laboratory work beta-lapachone triggers apoptosis (self-destruction) in tumor cells, and lapachol blocks vitamin K recycling in a way similar to warfarin. In a dish, lapachol and two anthraquinones from the bark stopped Helicobacter pylori growth at 2 to 8 micrograms per milliliter, against 32 for metronidazole and 0.063 for amoxicillin. A lapachol derivative, epoxy-α-lapachone, is active against the protozoa that cause leishmaniasis, Chagas disease and malaria. These are laboratory and animal findings, not results in people with gut complaints.

What has been tested in people

We could find no randomized trial of pau d’arco for any gut outcome: not for intestinal parasites, not for Helicobacter pylori, diarrhea or bloating. The Memorial Sloan Kettering summary says the antibacterial, antifungal and anticancer activity of pau d’arco comes from laboratory and animal studies and that human data are limited. Its list of human findings is short: preliminary results suggest a lapacho-based preparation may help prevent oral mucositis in head and neck cancer patients receiving radiotherapy, and may reduce pain in primary dysmenorrhea, while lapachol itself had no clinical effect in chronic myelocytic leukemia in an early clinical study.

The only human study of the bark capsule we could find is an open-label trial with no control group: 12 healthy women with primary dysmenorrhea took 1,050 mg a day for eight weeks. Nine of the 12 finished and nine reported an adverse event, most of them mild, and pain scores fell from baseline (p < .01). It says nothing about the gut.

The antiparasitic idea rests on the lab. The lapachol derivative epoxy-α-lapachone has shown activity against Leishmania, Trypanosoma cruzi and Plasmodium, which are parasites of blood and tissue and not intestinal worms or Giardia. Bark compounds stopped H. pylori in a dish. What has not been tested in people: pau d’arco against any intestinal parasite, stool-test results after use, the amount of lapachol in a capsule, and a dose that is both active and safe.

StudyDoseWhat it found
Open-label single-arm trial, 12 healthy women with primary dysmenorrhea (no control group; not a gut outcome) PMID 369603151,050 mg a day of encapsulated bark for 8 weeks9 of 12 finished; 9 of 12 reported an adverse event, mostly mild; pain intensity fell from baseline (p < .01)
Laboratory study of taheebo inner-bark compounds against Helicobacter pylori PMID 16359837In vitroLapachol minimum inhibitory concentration 4 micrograms/mL, versus 32 for metronidazole and 0.063 for amoxicillin; no human data
Review of epoxy-alpha-lapachone, a lapachol derivative, against protozoan parasites PMID 36731538In vitro and animalActivity reported against Leishmania, Trypanosoma cruzi and Plasmodium; none of these is an intestinal parasite
Review of red lapacho as an ethnopharmacological commodity PMID 18992801Not applicableBioscientific evidence insufficient; commercial bark varies in quality and composition; interference with vitamin K cycle noted
Memorial Sloan Kettering About Herbs summary of pau d'arcoNo dose givenHuman findings limited to preliminary oral mucositis and dysmenorrhea results; lapachol had no effect in chronic myelocytic leukemia; nausea, vomiting and urine discoloration reported

Doses used in trials and traditional preparations

No gut trial gives a dose. The one human study of the capsule used 1,050 mg a day of bark for eight weeks. The traditional preparation is a decoction of the inner bark. The Natural Medicines database says there is not enough scientific evidence to set a dose range, and the Memorial Sloan Kettering page lists none. Because products vary in lapachol content, and some products have been found lacking the labeled active ingredients, a label amount cannot be matched to an amount that has been studied.

Treat these figures as a record of what was studied. Whether any amount of pau d'arco suits a particular person is a question for a clinician or pharmacist who knows their history.

Safety

The Memorial Sloan Kettering summary reports nausea, vomiting and urine discoloration in an early clinical study of lapachol, and in animals anemia with large chronic doses, reduced seminal vesicle weight in mice, fetotoxicity and chromosomal abnormalities with oral lapachol. The Natural Medicines database rates oral use possibly unsafe at typical doses and likely unsafe at high doses, which it says can cause severe nausea, vomiting, diarrhea, dizziness and internal bleeding, and says anticancer research was halted because the doses needed may be poisonous. It rates pregnancy possibly unsafe at typical amounts and likely unsafe at larger ones, and says breastfeeding data are insufficient. Pau d’arco may slow clotting, and the database advises stopping at least two weeks before surgery.

Drug interactions

The main flag is with anticoagulant and antiplatelet drugs. Lapachol’s anticoagulant activity is attributed to inhibiting vitamin K epoxide reductase and quinone reductase, which Memorial Sloan Kettering likens to warfarin, so pau d’arco may add to the effect of warfarin, apixaban, clopidogrel, aspirin and heparins, and to anti-inflammatory painkillers that affect platelets such as ibuprofen and naproxen. The Natural Medicines database rates this moderate, and Memorial Sloan Kettering says the clinical relevance is not known. These ratings rest on lab mechanism and theory and not on interaction trials.

Prescriptions flagged alongside pau d'arco

Published interaction references put these medicines next to this herb, and the quiz acts on them; a pharmacist is the person to confirm any of it:

Products in the catalog with pau d'arco

These catalog entries list pau d'arco or one of its preparations among their active ingredients. Each page shows the amount on the label, the trials behind it and what buyers report.

Renew Life PARA SMART Cleansing Formula, 15-Day Program 4.2 out of 5 from 1,398 ratings from Amazon · ~$2.04 a day across the full 15-day program

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The questions that come up

Does pau d'arco kill intestinal parasites?

We could find no human trial testing pau d’arco against any intestinal parasite. Laboratory work on lapachol and its derivatives shows activity against blood and tissue protozoa such as Leishmania, and bark compounds stopped H. pylori in a dish. Those are lab findings and not results in people.

What is lapachol?

Lapachol is a naphthoquinone found in the heartwood and bark of Tabebuia trees and one of the two most studied compounds in pau d’arco. In laboratory work it blocks vitamin K recycling in a way similar to warfarin. Early clinical use of lapachol caused nausea, vomiting and urine discoloration.

Is pau d'arco safe with blood thinners?

The Natural Medicines database rates the interaction with anticoagulant and antiplatelet drugs as moderate, because pau d’arco may slow clotting and add to bruising and bleeding. Memorial Sloan Kettering says the clinical relevance is not known.

Do pau d'arco supplements contain what the label says?

Not always. The Natural Medicines database reports that some Canadian and Brazilian products lacked the active ingredients in the labeled amounts, and a review of red lapacho notes that commercial bark varies in quality and composition.

Is pau d'arco safe in pregnancy?

The Natural Medicines database rates oral use possibly unsafe at typical amounts and likely unsafe at larger amounts in pregnancy. Memorial Sloan Kettering notes that fetotoxicity has been reported with lapachol in animal work.

Sources