Safety & Side Effects
Pau d'Arco Side Effects and Safety: What You Need to Know
Important disclaimer
This article is for educational purposes only and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. Pau d'Arco is not intended to diagnose, treat, cure, or prevent any disease. We summarize published research and traditional use — this is not a recommendation to use Pau d'Arco for any specific condition. Always consult a qualified healthcare professional before starting a new supplement, especially alongside an existing medical condition or medication.
Pau d'Arco is often described as the "Divine Tree" of the Amazon, used for centuries by indigenous tribes. But "natural" doesn't mean "without rules." If you're considering it, it's worth understanding the safety profile as clearly as the benefits.
The Main Culprit: Lapachol
The primary active compound is a naphthoquinone called lapachol.
In the 1960s, the National Cancer Institute ran human trials on isolated lapachol because of its anti-tumor activity in animal models. To reach therapeutic blood levels, patients needed doses large enough to cause significant side effects — mainly nausea and blood-thinning effects. This is a study of the isolated, concentrated compound, not of drinking the whole-bark tea.
Source: NCI Phase I trials, 1960s–1970s
Traditional herbalists point out that whole inner bark (the phloem) contains other compounds that may moderate lapachol's intensity — which is why sourcing whole, authentic inner bark (rather than isolated extracts or fillers) matters; see our inner bark sourcing guide.
Common Side Effects
For most people, a standard decoction is well-tolerated. At higher doses or on an empty stomach, some people report:
- Nausea and vomiting — the most common reaction, especially with concentrated extracts.
- Dizziness or lightheadedness — occasionally reported at higher doses.
- Discolored urine — a slight color change (often deeper yellow or orange) generally considered a harmless byproduct of quinone metabolism.
- Diarrhea — at very high doses, the bark can act as a mild laxative.
If you experience these, the standard guidance is to reduce your dose or pause use.
Serious Interactions: The Blood-Thinning Factor
Research on Pau d'Arco extracts found inhibition of platelet aggregation — an "anti-vitamin K"-type effect that functions as a natural anticoagulant. This is extract-level research, but it's the basis for the drug-interaction cautions below.
Source: Journal of Ethnopharmacology (2006)
Because of this, avoid combining Pau d'Arco with:
- Prescription blood thinners — Warfarin (Coumadin), Heparin, Clopidogrel (Plavix).
- NSAIDs — Ibuprofen (Advil/Motrin), Naproxen (Aleve), high-dose Aspirin.
- Other blood-thinning herbs — garlic, ginger, turmeric, or ginkgo biloba, which can have an additive effect.
Surgery: stop all forms of Pau d'Arco at least two weeks before any scheduled surgery.
Who Should Avoid Pau d'Arco Entirely
- Pregnant women — animal studies have suggested lapachol may have abortifacient properties. Human safety data is sparse, but the risk is treated as high enough to contraindicate use during pregnancy.
- Nursing mothers — insufficient data on whether active compounds pass through breast milk.
- Infants and children — no established safe pediatric dosage.
- People with bleeding disorders — such as hemophilia.
Dosage and Preparation
Traditional and research sources both point to the decoction method — simmering the bark for 10–20 minutes — as standard. Avoid high-dose, isolated lapachol capsules; isolating one compound loses the whole-plant synergy, which is where toxicity concerns have historically shown up. See our brewing guide and Why the Inner Bark Is Important for more on why the whole inner bark, not an isolate, is the traditional and better-tolerated form.
A Note on Quality and Sourcing
Some reported "side effects" trace back to contaminants or low-grade fillers rather than Pau d'Arco itself — outer bark contains more tannins and fewer active compounds, which can irritate the stomach. Look for Handroanthus impetiginosus (formerly Tabebuia avellanedae) inner bark specifically; we source ours through Taheebo Wellness Tea.
Summary of Safety Precautions
- Start low and go slow — a small cup first, to see how your body reacts.
- Watch for unusual bruising, bleeding gums, or persistent nausea.
- Consider cycling use (e.g., five days on, two days off).
- Check your medications with your doctor if you're on any long-term prescriptions.
References
- 1.Molecules (2020): "Tabebuia impetiginosa: A Comprehensive Review on Traditional Uses, Phytochemistry, and Immunopharmacological Properties."
- 2.Journal of Ethnopharmacology (2006): "Inhibitory effects of Tabebuia impetiginosa inner bark extract on platelet aggregation."
- 3.Advanced Integrative Medicine (2022): "Safety and tolerability of pau d'arco (Tabebuia avellanedae) for primary dysmenorrhea."
- 4.Phytotherapy Research (2013): "Antiulcer effect of bark extract of Tabebuia avellanedae: activation of cell proliferation in gastric mucosa."
- 5.Genetics and Molecular Biology (2012): "Genotoxic effects of Tabebuia impetiginosa extract in Wistar rats."
- 6.National Cancer Institute (NCI): Historical data on lapachol Phase I clinical trials.