Pau d'Arco

What is Pau d'Arco?

Pau d'Arco refers to the dried inner bark of Tabebuia impetiginosa (synonym: Handroanthus impetiginosus), a large flowering tree found throughout Central and South America, particularly in Brazil, Argentina, and Paraguay. Indigenous peoples of the Amazon and Inca regions have used it medicinally for centuries, particularly for infections, fevers, and inflammation. The bark is harvested, dried, and prepared as a decoction, tincture, or powdered supplement.

How does Pau d'Arco work?

The primary bioactive compounds in Pau d'Arco are naphthoquinones, most notably lapachol and beta-lapachone. These compounds have demonstrated antifungal activity in laboratory settings by disrupting fungal cell membrane integrity and electron transport chains. Beta-lapachone in particular has been studied for its ability to interact with NAD(P)H quinone oxidoreductase (NQO1), an enzyme involved in oxidative stress regulation, which underlies both its potential anti-infective and anti-inflammatory properties.

What forms does Pau d'Arco come in?

Traditional preparation involves simmering the dried inner bark for 15–20 minutes to make a tea, which is the form with the longest historical record. Capsules and tablets typically contain standardized or unstandardized bark powder or extract. Tinctures use alcohol extraction and may concentrate certain constituents differently than aqueous decoctions. Standardization for lapachol content is not universally practiced, making product potency variable across brands.

Where it comes from:

Pau d'Arco has been used in Amazonian and Andean traditional medicine for centuries, with documented use among the Guarani, Tupi, and Inca peoples for conditions including fevers, malaria, syphilis, and fungal skin infections. In the 1960s–1970s, Brazilian researchers and the U.S. National Cancer Institute investigated lapachol as a potential anticancer agent, but clinical trials were halted due to toxicity at effective doses. Interest in the whole bark (rather than isolated lapachol) has continued in herbal medicine.

What does Pau d'Arco help with?

• Candida/Fungal Infections: Lapachol and beta-lapachone have demonstrated in vitro antifungal activity against Candida albicans and other Candida species by impairing mitochondrial electron transport and disrupting fungal cell membrane function. This is the most frequently cited mechanism in the herb's traditional use. However, the evidence base is almost entirely from laboratory cell and culture studies; no rigorous human RCTs have confirmed clinically meaningful reductions in candidal infections from oral Pau d'Arco supplementation, and the concentration required in vitro may not be reliably achieved in vivo at safe oral doses.
• Immune Support: Naphthoquinone compounds from Pau d'Arco have been shown in cell-based studies to modulate macrophage activation and cytokine signaling, including effects on NF-kB pathways involved in immune response regulation. Traditional use for febrile and infectious illnesses is consistent with these mechanistic findings. Human clinical evidence for this application is absent, and any immune-modulating effect in humans at doses found in commercial supplements remains unconfirmed.
• Inflammatory Conditions: Beta-lapachone and other naphthoquinones have shown anti-inflammatory activity in cell culture and animal models by suppressing pro-inflammatory mediators including TNF-alpha, IL-6, and COX-2 activity. These findings form the rationale for its traditional use in arthritic and inflammatory complaints. Direct human clinical data are lacking; the evidence is mechanistic and preclinical, and translation to oral supplementation in humans has not been formally tested in controlled trials.
• Bacterial Infections (adjunctive/topical): Pau d'Arco bark extracts have demonstrated in vitro antibacterial activity against a range of gram-positive organisms, including Staphylococcus aureus and Helicobacter pylori, primarily attributed to quinone-mediated disruption of bacterial electron transport and membrane integrity. Topical use in traditional medicine for skin infections is consistent with this mechanism. No human RCTs support systemic use as an antibiotic, and this application should be considered exploratory and adjunctive only.

What are the side effects of Pau d'Arco?

• Nausea and vomiting (dose-dependent; more common at higher doses)
• Diarrhea or loose stools
• Anticoagulant effect / increased bleeding time (established for lapachol; dose-dependent)
• Dizziness
• Anemia (at high/sustained doses, based on NCI lapachol trial data)
• Potential liver stress at high doses or with prolonged use
• Contraindicated in pregnancy (potential uterotonic/abortifacient effects based on traditional use and animal data)

Good to know:

At doses found in typical commercial supplements and teas, Pau d'Arco is generally considered low-risk for short-term use in healthy adults. However, the isolated compound lapachol is known to be toxic at higher doses—NCI trials in the 1970s discontinued lapachol due to nausea, vomiting, anticoagulant effects, and anemia at doses needed for therapeutic blood levels. Whole-bark preparations contain lower lapachol concentrations, but caution is warranted, particularly in pregnancy, liver disease, or with concurrent anticoagulant use.

How much Pau d'Arco should you take?

• Recommended daily: Traditional tea: 20–30g dried bark simmered in 1 liter of water, consumed throughout the day (approximately 2–3 cups). Capsule/extract: manufacturers typically recommend 500–1000mg standardized bark extract 2–3 times daily. No human RCT-validated therapeutic dose exists; these are convention-based ranges only.
• Best time of day: No evidence-based guidance; traditionally taken as a tea spread throughout the day rather than in a single large dose.
• With or without food: Taking with food is recommended to reduce gastrointestinal side effects such as nausea.
• Time to effect: Traditional use suggests 2–6 weeks of consistent use for observable effects; no controlled human data define an onset window.
• How long to take it: Typically used for 4–8 week courses in traditional herbal medicine, followed by a break. Long-term continuous use is not supported by safety data and is not recommended. Avoid in pregnancy at any duration.