Pau d'Arco
StarHandroanthus impetiginosus (Mart. ex DC.) Mattos
Safety at a glance
No rule in our tables for this herb: pregnancy, breastfeeding, incompatible pairs (十八反 / 十九畏), herb–drug, dose ceiling. This is not a safety clearance.
Not graded — No toxicity grade is recorded. Most herbs in the catalogue carry none.
Traditionally used for
- Colds & fever
- Digestion
- Urinary & fluids
- Skin
Cautions & contraindications
- Pregnancy
- Breastfeeding
- Bleeding disorders
☯ TCM Properties
Drains Damp-Heat from the Lower Jiao; Clears and Eliminates Damp-Heat from the skin; Dissolves Damp Toxins; Invigorates Qi and Blood (anti-tumor)
Traditional Chinese Uses
Pau d'Arco (lapacho) is the inner bark of the South American tree Handroanthus impetiginosus (formerly Tabebuia impetiginosa/avellanedae). It is not part of the classical Chinese materia medica but has been adopted into modern Western herbal and integrative practice, where it is described in TCM terms as neutral and sweet-salty, entering the Stomach, Spleen, Bladder and Liver channels. In this framework it is used to drain Damp-Heat from the Lower Jiao, to clear Damp-Heat and toxins from the skin in conditions such as fungal infections, eczema and sores, and—on the strength of its naphthoquinones (lapachol, beta-lapachone)—has been explored for anti-tumour and antimicrobial effects.
Traditionally in South America the bark decoction was taken for infections, inflammation, fever and cancer. Evidence for these uses is largely preliminary, and high or prolonged doses can cause nausea, gastrointestinal upset and a bleeding tendency.
Click a node for details · double-click to expand it · Ctrl/⌘ + scroll or two fingers to zoom and pan.
Botanical Description
The name Ban Zhen Zhong Hua Shu (literally something like 'spotted-needle middle-flower tree') does not match any standard Chinese materia medica reference verifiable to the editor at the time of this record. The phrase may represent a regional folk name, a transcription variant, a non-medicinal botanical name carried over from a generic plant database, or a corrupted or composite entry. Without a confident pinyin-to-Latin binomial mapping, no botanical description, habitat data, or morphological characters can be responsibly provided. The record is retained as a placeholder pending further bibliographic research, possible cross-referencing to provincial Chinese floras, or correction of the source pinyin string. All medicinal-attribute fields are left null to avoid fabrication of identification or properties.
Active Constituents
Lapachol
Prenylated 1,4-naphthoquinone (2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone)Concentration: Concentrated in the heartwood and inner bark; commercial bark preparations are frequently very low in it or free of it altogether, and it is largely absent from outer bark
The marker compound and the source of most of the drug's hazard. It inhibits vitamin K epoxide reductase and vitamin K quinone reductase, the same enzymes warfarin acts on, giving it genuine anti-vitamin K anticoagulant activity. It has antineoplastic and antimicrobial activity in vitro, but a human phase I trial could not reach an antitumour plasma concentration without toxicity. In rodents it is fetotoxic, reduces seminal vesicle weight, causes anaemia on chronic dosing and is clastogenic.
beta-Lapachone
ortho-Naphthoquinone (1,2-naphthoquinone)Concentration: A minor constituent of the bark relative to lapachol; most published pharmacology uses isolated or synthetic material rather than bark extract
Bioactivated by NAD(P)H:quinone oxidoreductase 1 to generate reactive oxygen species and futile redox cycling, and reported to downregulate COX-2 and telomerase, induce Egr-1 and trigger caspase-dependent apoptosis in tumour cell lines. It has been taken into oncology trials as a single synthetic agent (ARQ 761), which is a separate matter from what a bark decoction delivers.
Furanonaphthoquinones
Naphtho[2,3-b]furan-4,9-dione derivativesConcentration: Minor bark constituents
The most cytotoxic fraction of the bark in vitro and largely responsible for the antibacterial activity reported against Helicobacter pylori and methicillin-resistant staphylococci. Cytotoxicity in these assays is not selective for tumour cells.
Cyclopentene dialdehydes
Cyclopentene dialdehydeConcentration: Minor bark constituents isolated from Tabebuia impetiginosa bark
Reactive dialdehydes isolated from the bark and reported to contribute to its antimicrobial activity. They are among the constituents that make crude bark preparations chemically more complex than the lapachol content alone would suggest.
Acteoside (verbascoside)
Phenylethanoid glycosideConcentration: A polar bark constituent, and therefore a substantial part of what an aqueous decoction actually extracts
An antioxidant and anti-inflammatory phenylethanoid glycoside. Because it is water-soluble while lapachol is not, decoctions of the bark deliver a very different constituent profile from the alcoholic extracts and isolated quinones used in most of the pharmacology literature.
⚠ Drug Interactions
Warfarin and other vitamin K antagonists, direct oral anticoagulants, heparins and antiplatelet drugs
This is not an extrapolation from a class effect. Lapachol was shown in 1984 to inhibit vitamin K epoxide reductase and vitamin K quinone reductase, which is warfarin's own mechanism, and anti-vitamin K activity was one of the toxicities that limited dosing in the 1974 phase I oncology trial of lapachol in humans. Inner bark extract has separately been shown to inhibit platelet aggregation through suppression of arachidonic acid liberation and ERK1/2 activation, so bleeding risk arrives by two routes. The complication is that the magnitude is unpredictable in practice because commercial bark products vary from lapachol-rich to lapachol-free.
Clinical note: Do not combine with anticoagulants or antiplatelet drugs outside specialist supervision. If a patient on warfarin has been taking pau d'arco, check the INR rather than assuming the product was inert. Stop at least two weeks before any planned surgery or dental extraction, and stop if unexplained bruising, epistaxis or gum bleeding appears.
Other Tabebuia, Handroanthus and Tecoma species and outer-bark or sapwood material sold as pau d'arco or lapacho
The genus formerly treated as Tabebuia was split in 2007, and the medicinal drug is Handroanthus impetiginosus, previously Tabebuia impetiginosa or T. avellanedae. Several other Tabebuia, Handroanthus and Tecoma species with little or no naphthoquinone content continue to be traded under the same vernacular names, and outer bark, sapwood and wood chips - which are low in naphthoquinones compared with the inner bark - are common substitutes. Chemical surveys of retail pau d'arco have repeatedly found lapachol at trace levels or below detection in most products. The consequence cuts both ways: an inert product will not work, while an unexpectedly quinone-rich one will interact with anticoagulants.
Clinical note: Insist on inner bark of Handroanthus impetiginosus with the binomial on the label, and treat vernacular-only labelling ('pau d'arco', 'lapacho', 'taheebo', 'ipe roxo') as unidentified material. Do not conclude from an absence of effect that the drug is safe to combine with an anticoagulant, because the next batch may differ.
Pregnancy, breastfeeding and attempts to conceive
Lapachol crosses the placenta and reduced fetal growth in rats, produced reproductive toxicity including reduced seminal vesicle weight in male rodents on short-term treatment, and induced clastogenic effects in rats. Chronic dosing also produced anaemia in animal studies. The anti-vitamin K activity adds an independent concern in pregnancy, since vitamin K antagonism in the first trimester is a recognised teratogenic mechanism from the warfarin literature.
Clinical note: Do not prescribe in pregnancy, when trying to conceive, or during breastfeeding. This is a hard contraindication, not a precaution.
Immunosuppressants in transplant recipients
Tabebuia avellanedae extracts inhibited interleukin-2-independent T-lymphocyte activation and proliferation in vitro, which is why the extract was examined in a transplant immunology setting at all. No human pharmacokinetic or pharmacodynamic interaction study with ciclosporin, tacrolimus or mycophenolate has been published, and no systemic exposure data exist, so this remains a laboratory observation rather than a documented clinical interaction.
Clinical note: Flag it in transplant recipients and advise against unsupervised use, but do not adjust immunosuppressant dosing on the basis of it.
Dosage Calculator
⚖ Dosage Calculator
A weight-based mathematical estimate for Pau d'Arco. Not a prescription.
Evidence Tier
4 studies on recordRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
0
Randomized controlled trial
0
Other clinical trial
3
1 verified · 2 unverified
Show 3 studies
- Early clinical studies with lapachol (NSC-11905)
- Safety and tolerability of Pau d′ Arco (Tabebuia avellanedae) for primary dysmenorrhea: A single-arm, open-label trial on adults ages 18–45
- Oral Lapacho-Based Medication: An Easy, Safe, and Feasible Support to Prevent and/or Reduce Oral Mucositis During Radiotherapy for Head and Neck Cancer
Observational / case report
0
In vitro / animal
1
1 verified · 0 unverified
Other / unclassified
0
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
Lapachol inhibition of vitamin K epoxide reductase and vitamin K quinone reductase
Lapachol was shown to inhibit both vitamin K epoxide reductase and vitamin K quinone reductase, establishing that its anticoagulant action operates through the same enzymatic targets as warfarin rather than through a vaguer antiplatelet mechanism. This is the mechanistic foundation for treating the pau d'arco-anticoagulant interaction as pharmacodynamically real.
Early clinical studies with lapachol (NSC-11905)
The phase I evaluation of lapachol as an anticancer agent in patients. Plasma concentrations associated with antitumour activity could not be reached without toxicity, the reported effects including nausea, vomiting and anti-vitamin K activity. The trial is the reason lapachol was abandoned as a drug candidate, and it is also the only human evidence that the anticoagulant effect of the compound is expressed in people rather than only in enzyme assays.
Safety and tolerability of Pau d′ Arco (Tabebuia avellanedae) for primary dysmenorrhea: A single-arm, open-label trial on adults ages 18–45
Twelve healthy women aged 18-45 with primary dysmenorrhea took 1050 mg/day of encapsulated Tabebuia avellanedae for eight weeks, with prothrombin time and haemoglobin monitored specifically because of the known anti-vitamin K and anaemia signals. Nine of twelve completed. Nine of twelve reported an adverse event, mostly mild, and none met the FDA definition of serious; laboratory markers largely stayed within normal limits with a few mild abnormalities. Pain intensity fell significantly after the first dose and at four and eight weeks, while quality of life, pain interference and hs-CRP changed only non-significantly. With no control arm and twelve participants this is a tolerability signal, not evidence of efficacy.
Oral Lapacho-Based Medication: An Easy, Safe, and Feasible Support to Prevent and/or Reduce Oral Mucositis During Radiotherapy for Head and Neck Cancer
Forty consecutive adults receiving radiotherapy for head and neck cancer took a swallowable lapacho-based solution three times daily from day one until the end of treatment. Eleven (27.5%) developed grade 2 oral mucositis and four (10%) grade 3, none grade 4, and no patient discontinued radiotherapy because of mucositis. The product was well tolerated. There was no control arm, so the mucositis rates cannot be attributed to the intervention, and the authors call for a phase III trial.
References
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
📝 Notes
Public notes from the community and your own private notes on Pau d'Arco.
No notes yet.