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Herb library · Herb · Handroanthus impetiginosus (syn. Tabebuia impetiginosa, T. avellanedae)

Pau d'arco

The inner bark of a South American flowering tree, sold as a tea and in capsules, and promoted since the 1960s for cancer and infections. Lab studies of its compounds are extensive; studies in people are few, small and uncontrolled, and a 2009 review called the evidence insufficient.

Traditional use

Red lapacho is a canopy tree of the Amazon and other parts of South America. A decoction of the inner bark is used in local traditional medicine for bacterial and fungal infections, fever, syphilis, malaria and stomach and bladder complaints. In the 1960s Brazilian press reports of "miraculous" results in cancer patients made it famous, and the U.S. National Cancer Institute studied the tree in considerable detail. Its two main active compounds are lapachol and beta-lapachone.

What studies show

  • Insufficient

    Cancer: its compounds kill cancer cells in the lab, but a 2009 review called the evidence for pau d'arco products insufficient, and a 2022 review of the whole genus described results against tumor cells in the lab and called the toxicology inconclusive.

  • Insufficient

    Menstrual pain: in a 2022 single-arm trial, 12 healthy women took 1,050 mg a day of pau d'arco capsules for eight weeks. Pain scores fell compared with before, but there was no comparison group, three women did not finish, and nine reported side effects, mostly mild.

  • Insufficient

    Mouth sores during radiotherapy: a 2015 phase II study of 40 people with head and neck cancer found a lapacho-based oral solution was well tolerated; without a comparison group it cannot show whether it helped.

Be careful of

Cautions

  • InteractionLapachol, one of its compounds, interferes with vitamin K, which the body needs for blood clotting (2009 review), and the trial authors note that lapachol has caused anticoagulation at doses far above theirs. Do not combine it with blood thinners such as warfarin without a clinician.
  • NoteIn the 2022 trial, side effects included nausea, vomiting, diarrhea, dizziness and one person's nosebleeds (her clotting tests stayed normal).
  • NoteProducts on the international market vary in quality and composition (2009 review), so what is in a given bark or capsule is uncertain.
  • ConditionIt is not a substitute for cancer care. Anyone with cancer should talk with their oncology team before taking it.
  • Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.

Sources

  1. Red Lapacho (Tabebuia impetiginosa)--a global ethnopharmacological commodity? (J Ethnopharmacol, 2009) (opens in a new tab) · NIH · read September 25, 2026
  2. Anticancer potential and toxicity of the genus Handroanthus Mattos (Bignoniaceae): A systematic review (Toxicon, 2022) (opens in a new tab) · NIH · read September 25, 2026
  3. 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) (opens in a new tab) · NIH · read September 25, 2026
  4. Safety and tolerability of Pau d' Arco (Tabebuia avellanedae) for primary dysmenorrhea: A single-arm, open-label trial on adults ages 18-45 (full text, PubMed Central) (opens in a new tab) · NIH · read September 25, 2026
  5. Oral Lapacho-Based Medication: An Easy, Safe, and Feasible Support to Prevent and/or Reduce Oral Mucositis During Radiotherapy for Head and Neck Cancer (Nutr Cancer, 2015) (opens in a new tab) · NIH · read September 25, 2026

Reviewed September 25, 2026.