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Pau d’Arco is a supplement derived from the bark of the Tabebuia avellanedae tree. It contains the compounds lapachol and beta-lapachone, and has been used traditionally to treat fungal infections, inflammation and certain cancers. Despite its natural origin, pau d’arco can potentially cause dangerous side effects when taken in excess or with certain medications. Understanding the side effects of paul d’arco can help prevent unnecessary dangers associated with the supplement.


Nausea is a relatively common side effect of pau d’arco. It may be more severe with higher doses, but it can still occur when regular or low doses are taken. In some cases, nausea may lead to vomiting, which can cause electrolyte imbalances and dehydration if prolonged.

To help prevent nausea when taking pau d’arco, start with the lowest effective dose. Brewing the herb into a tea and drinking it slowly may help prevent the nausea that occurs with pau d'arco in capsule form.


Bleeding is one of the more serious side effects of pau d’arco. According to the National Institutes of Health, pau d’arco can impair blood clotting by interfering with the metabolism of vitamin K. Undetected or prolonged bleeding may lead to anemia and can be fatal if it occurs internally.

Bleeding risks are greatest when pau d’arco is taken in high doses or with blood thinners like aspirin or clopidogrel. People with a history of blood clotting disorders like hemophilia should avoid using pau d’arco due to the risk of uncontrolled bleeding.


Diarrhea may occur when taking normal doses of pau d’arco. While it’s generally viewed as a minor inconvenience, diarrhea can cause severe health problems when prolonged such as dehydration, nutrient deficiencies and weight loss. Occasionally, other gastrointestinal symptoms like vomiting, nausea and cramping may occur in conjunction with diarrhea.

Liver Damage

Liver damage is a rare but extremely serious side effect of pau d’arco. Hydroquinone—a compound with both medicinal and toxic properties—is largely responsible for pau d’arco’s effects on the liver. To help prevent liver damage, use a low dose of pau d’arco. Do not take it with other liver toxins like acetaminophen or alcohol, and avoid use altogether if you have a history of liver disease or alcoholism.

Drug Interactions

Pau d’arco may cause serious or life-threatening effects when taken with certain herbs or medications. Because it thins the blood, pau d’arco should not be taken with prescription blood thinners like Coumadin or clopidogrel, according to the University of Maryland Medical Center. Herbs like ginger, turmeric and willow bark may also increase bleeding risks when taken with pau d’arco. Other potential interactions include over-the-counter pain relievers like ibuprofen, aspirin and naproxen.