Pau D’Arco is the common name for several species of large trees native to Brazil and Argentina, the most common of which is Hydroanthus (Tabebuia) impetiginosa. It has history of at least 1,000 years of use by indigenous groups, including the Inca, as a treatment for malaria and for gastrointestinal, skin, and rheumatologic conditions. The inner bark of the tree is the part used as medicine.
I discussed the benefits and risks of taking pau d’arco with David S. Kiefer, M.D., clinical assistant professor, in the Department of Family Medicine at the University of Wisconsin School of Medicine and Public Health. Dr. Kiefer studied herbal medicine while attending medical school and during his integrative medicine fellowship at the University of Arizona. He has written and lectured extensively on the topic for almost 20 years.
After its introduction to western medicine and the isolation of numerous medicinally active phytochemicals, Dr. Kiefer says that pau d’arco gained a reputation for curing cancer, fighting chronic fungal infections, and boosting immunity. For example, lapachol, one of the compounds in pau d’arco, has demonstrated possible immune system enhancing, anti-fungal, anti-parasitic, and anti-tumor effects in laboratory and animal models. Dr. Kiefer notes that these effects may also be due to other constituents in the bark. Like other herbal medicines, pau d’arco contains a diverse “family” of compounds that probably work synergistically to affect human physiology. While there is some biochemical evidence supporting the clinical effects attributed to pau d’arco, he makes the point that convincing human trials are lacking.
On balance, Dr. Kiefer regards using pau d’arco as potentially unsafe. Toxicity (dizziness, nausea, vomiting, teratogenicity) has been reported at high doses, and because it may thin the blood, it is important to be cautious when using this supplement if you’re taking prescription blood thinners such as Coumadin. Also, pau d’arco may counteract the immunosuppressant effects of some drugs used to treat autoimmune and other diseases.
Your question about reliable sources for pau d’arco products highlights an important issue. Dr. Kiefer says that when they were tested, some of the supplements that used to be on the market had less than the expected amount of lapachol. He notes that ConsumerLab, a third-party testing organization, has reviewed many herbal medicines and lists relevant reputable brands but has not done this yet for pau d’arco. He says that if he extrapolates from the quality of products offered by companies with good reputations, the tincture available from Herb Pharm and the capsules of the bark made by Nature’s Way would be reasonable choices.
However, given the lack of convincing effectiveness, and some safety concerns, Dr. Kiefer says he’s less than impressed with pau d’arco for its immune system boosting or anti-cancer effects. He advises consulting an herbal expert or integrative medicine practitioner to help guide your choice about plant-based remedies that might be beneficial for you.
Andrew Weil, M.D.
S. Mills and K. Bone, “Principles and Practices of Phytotherapy: Modern Herbal Medicine.” Churchill Livingstone: Edinburgh; 2000
Francis Brinker, “Herbal Contraindications and Drug Interactions Plus Herbal Adjuncts With Medicines”. Sandy, Oregon; Eclectic Medical Publications: 2010
K. Bone and A. Pengelly, “Pau d’arco: part 1”. MediHerb Professional Review. May 1997;57:1-2