Home Ingredients Pau D'Arco Bark Extract
Immune Support

Pau D'Arco Bark Extract

Tabebuia avellanedae / Handroanthus impetiginosus
Evidence Level
Preliminary
2 Clinical Trials
4 Documented Benefits
1/5 Evidence Score

Pau D'Arco (also called Lapacho or Taheebo) is the inner bark of South American trees in the Tabebuia/Handroanthus genus, used in traditional Brazilian and indigenous medicine. Its major bioactives are naphthoquinones — most notably lapachol and beta-lapachone — which exhibit antimicrobial, antifungal, and cytotoxic activity in preclinical (cell and animal) studies. Lapachol itself was advanced into a National Cancer Institute Phase I anticancer trial but was withdrawn from further development because of unacceptable systemic toxicity, including prothrombin-time prolongation consistent with anti-vitamin-K effects. Modern supplement use is largely traditional; rigorous human evidence is sparse. Use bark-only commercial extracts at modest doses and avoid in pregnancy or when anticoagulated.

Studied Dose The one human study used 1,050 mg/day of encapsulated bark for 8 weeks; traditional use is 500 to 1,000 mg 1 to 3 times daily. Avoid in pregnancy and on anticoagulants.
Active Compound Naphthoquinones: lapachol, beta-lapachone, alpha-lapachone and related quinones; also iridoid and benzoic acid derivatives.

Benefits

Traditional Immune Support

Pau D'Arco has been used in traditional South American medicine as a general immune tonic. Preclinical evidence shows naphthoquinones can inhibit growth of certain bacteria, yeasts, and parasites in vitro, which informs the supplement's marketed immune-support positioning.

Supported by Trial 2

Antifungal Tradition

Lapachol and related quinones display activity against Candida and other fungi in laboratory assays. Pau D'Arco is widely used in folk and integrative practice for yeast-balance protocols, though high-quality human trial data is limited.

Supported by Trial 2

Antioxidant Bark Compounds

The polyphenolic and quinone fraction of Pau D'Arco bark exhibits free-radical scavenging activity in vitro. This may contribute to its traditional reputation as a 'cleansing' or restorative tonic in indigenous and folk practice.

Supported by Trial 2, Trial 1

Inflammation: Preclinical Signals Only

Naphthoquinones from the bark suppress NF-kB signaling and inflammatory cytokines in cell and animal models. In the single human oral trial, an uncontrolled study in menstrual pain, the inflammation marker hs-CRP did not change significantly, so an anti-inflammatory effect in people is not established.

Supported by Trial 2

Mechanism of action

1

Naphthoquinone Redox Cycling

Lapachol and beta-lapachone undergo enzymatic redox cycling, generating reactive oxygen species in laboratory studies. This chemistry underlies the bark's traditional antimicrobial use but also contributes to its systemic toxicity at higher doses.

2

Topoisomerase Inhibition

Beta-lapachone inhibits topoisomerase I, a DNA-processing enzyme upregulated in rapidly dividing cells. This action was the basis for early preclinical anticancer interest, though clinical development was limited by off-target toxicity.

3

Anti-Vitamin-K Activity

Lapachol's quinone structure resembles vitamin K and competes with K-dependent clotting factor activation, prolonging prothrombin time at higher doses. This pharmacologic effect was a documented dose-limiting toxicity in the historical NCI Phase I trial.

4

NQO1 Substrate

Beta-lapachone is a substrate for NAD(P)H quinone dehydrogenase 1 (NQO1), an enzyme often elevated in stressed or transformed cells. NQO1-mediated bioactivation generates oxidative stress preferentially in tissues expressing this enzyme.

Clinical trials

1
Lapachol Phase I Anticancer Trial — Historical

Phase I clinical trial conducted in the 1970s by the National Cancer Institute investigating lapachol (the major naphthoquinone from Pau D'Arco) for anticancer activity in patients with advanced malignancies.

Adults with advanced solid tumors in early-phase oncology testing.

Lapachol produced dose-limiting toxicity, including prothrombin-time prolongation consistent with anti-vitamin-K effects, anemia, and gastrointestinal symptoms. Development was discontinued. The trial establishes that the active naphthoquinone from Pau D'Arco produces measurable systemic effects at supratherapeutic doses and informs current safety framing — particularly the contraindication with anticoagulant therapy.

2
Preclinical Antimicrobial and Antifungal Activity

Series of in vitro and animal studies evaluating Pau D'Arco bark extract and isolated naphthoquinones against bacterial, fungal, and parasitic organisms.

Cell culture and rodent infection models.

Pau D'Arco extracts and isolated lapachol/beta-lapachone show measurable inhibitory activity against Candida albicans, Staphylococcus aureus, and select parasites in laboratory assays. Animal models suggest some in vivo efficacy. Translation to clinical antimicrobial dosing in humans has not been established by controlled trials.

Side effects and drug interactions

Common Potential side effects

Anti-vitamin-K bleeding risk: at high doses lapachol can prolong prothrombin time and increase bleeding susceptibility.
Gastrointestinal upset: nausea, vomiting, or diarrhea at higher doses or prolonged use.
Anemia has been reported in early clinical use of high-dose lapachol.
Avoid in pregnancy and breastfeeding due to historical reports of teratogenicity in animal studies.
Quality varies widely; some commercial products mix inner and outer bark — choose reputable suppliers.

Important Drug interactions

Warfarin and other anticoagulants — additive bleeding risk from anti-vitamin-K activity; avoid combination
Antiplatelet drugs (aspirin, clopidogrel) — increased bleeding risk; use only with prescriber oversight
Chemotherapy agents — quinone redox cycling may interact unpredictably; avoid during active cancer treatment without oncologist input
NSAIDs — additive gastrointestinal and bleeding risk at higher Pau D'Arco doses

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Frequently asked questions about Pau D'Arco Bark Extract

What is pau d'arco used for?

Pau d'arco is the inner bark of a South American tree, used traditionally for immune support and as an antimicrobial and antifungal (including for candida and yeast concerns). It contains compounds called naphthoquinones (like lapachol).

What is pau d'arco good for?

It is traditionally used for immune support, fungal and yeast overgrowth, and inflammatory and skin conditions. Human evidence is largely traditional and preliminary, so claims should be viewed cautiously.

How much pau d'arco should I take?

It is used as a tea (decoction of the bark), tincture, or capsule; follow product labeling. Traditional use involves simmering the bark.

Is pau d'arco safe?

In moderate traditional amounts it is generally tolerated, but high doses can cause nausea, and its lapachol content may have blood-thinning effects and other toxicity at high intake. Pregnant women should avoid it, and those on anticoagulants should check with a doctor.

What is Pau D'Arco Bark Extract?

Pau D'Arco (also called Lapacho or Taheebo) is the inner bark of South American trees in the Tabebuia/Handroanthus genus, used in traditional Brazilian and indigenous medicine.

What is Pau D'Arco Bark Extract used for?

Pau D'Arco Bark Extract is researched primarily for Immune Support. Pau D'Arco has been used in traditional South American medicine as a general immune tonic. Preclinical evidence shows naphthoquinones can inhibit growth of certain bacteria, yeasts, and parasites in vitro, which informs the supplement's mar…

What is the recommended dosage of Pau D'Arco Bark Extract?

The clinically studied dose is The one human study used 1,050 mg/day of encapsulated bark for 8 weeks; traditional use is 500 to 1,000 mg 1 to 3 times daily. Avoid in pregnancy and on anticoagulants. Always follow the product label and check with a healthcare provider for personal advice.

Is Pau D'Arco Bark Extract safe, and does it have side effects?

For most healthy adults, Pau D'Arco Bark Extract is well tolerated at studied doses. Reported effects can include: Anti-vitamin-K bleeding risk: at high doses lapachol can prolong prothrombin time and increase bleeding susceptibility. Gastrointestinal upset: nausea, vomiting, or diarrhea at higher doses or prolonged use. It may also interact with some medications. Pau D'Arco Bark Extract is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Pau D'Arco Bark Extract interact with any medications?

Possible interactions include: Warfarin and other anticoagulants — additive bleeding risk from anti-vitamin-K activity; avoid combination Antiplatelet drugs (aspirin, clopidogrel) — increased bleeding risk; use only with prescriber oversight If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Pau D'Arco Bark Extract?

NutraSmarts rates the evidence for Pau D'Arco Bark Extract as Preliminary (1 out of 5). It is backed by 2 clinical trials and 4 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(4 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. McKelvey EM, Lomedico M, Lu K, Chadwick M, Loo TL. Dichloroallyl lawsone. Clin Pharmacol Ther. 1979;25(5 Pt 1):586-90. doi: 10.1002/cpt1979255part1586.PubMedUsed to support: Phase I pharmacokinetic study in cancer patients of dichloroallyl lawsone (NSC-126771), a synthetic intravenous analogue of lapachol and not lapachol or pau d'arco itself. Dose-limiting toxicity in this compound was cardiac. Included only as class-level context for naphthoquinone drug toxicity, not as evidence for pau d'arco.
  2. Maeda M, Murakami M, Takegami T, Ota T. Promotion or suppression of experimental metastasis of B16 melanoma cells after oral administration of lapachol. Toxicol Appl Pharmacol. 2008;229(2):232-8. doi: 10.1016/j.taap.2008.01.008.PubMedUsed to support: In mice, a single high toxic oral dose of lapachol (80 to 100 mg/kg) sharply increased experimental B16 melanoma metastasis by inducing a vitamin K-dependent hypercoagulable state; only low non-toxic doses weakly reduced metastasis. Animal data only, illustrating the narrow safety margin of pau d'arco's main naphthoquinone.
  3. McClure C, Bollen M, Buttolph L, Stack E, Langley BO, Hanes D, Wright KM, Tibbitts D, Bradley R. Safety and tolerability of Pau d' Arco (Tabebuia avellanedae) for primary dysmenorrhea: A single-arm, open-label trial on adults ages 18-45. Adv Integr Med. 2022;9(3):159-166. doi: 10.1016/j.aimed.2022.04.003.PubMedUsed to support: The only human oral trial of pau d'arco: a single-arm, open-label study with no placebo giving 1,050 mg/day of encapsulated bark for 8 weeks to 12 women with menstrual pain. It was primarily a safety study, and prothrombin times and anemia markers mostly stayed within normal limits. Pain fell versus each woman's own baseline, but without a control group this cannot be attributed to the herb, and the inflammation marker hs-CRP did not change significantly.
  4. Block JB, Serpick AA, Miller W, Wiernik PH. Early clinical studies with lapachol (NSC-11905). Cancer Chemother Rep 2. 1974;4(4):27-8..PubMedUsed to support: Early National Cancer Institute clinical study of oral lapachol, pau d'arco's principal naphthoquinone, in cancer patients. It is the historical clinical evaluation of lapachol, which was not advanced further as a drug, and it provides no evidence of benefit from pau d'arco as a supplement.