Loose sifted Pau D’arco from the Brazilian Amazon is used in this tincture, yes, only one ingredient besides solvent! Pau d'arco contains chemical compounds called naphthoquinones, specifically lapachol and beta-lapachone.
 
What's It Made Of?
 
Most of the chemical research on pau d'arco has been done on the wood and not the inner bark. Pau d'arco contains chemical compounds called naphthoquinones, specifically lapachol and beta-lapachone. They seem to have antifungal, antiviral, and antibacterial properties. They also contain significant amounts of the antioxidant quercetin.
 
Dosage 
 
It is important to discuss the dose with your provider, since large amounts of pau d'arco can be toxic. The risk of side effects seems to be greater when the dose of lapachol is more than 1.5 g per day. However, it can be hard to determine how much lapachol the powdered bark contains.
 
Precautions
 
The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, can trigger side effects, and can interact with other herbs, supplements, or medications. For these reasons, you should take herbs with care, under the supervision of a health care provider.
Talk to your provider to determine the proper dose of pau d'arco because too much can be dangerous.
At recommended doses, side effects are uncommon but may include anemia, nausea, diarrhea, and dizziness.
High doses can cause uncontrolled bleeding and vomiting.
Pregnant and nursing women should not take pau d'arco.
 
Possible Interactions
 
Antiplatelet and anticoagulant drugs (blood thinners)
Pau d'arco may affect the blood's ability to clot, and could interfere with blood-thinning drugs, including:
Warfarin (Coumadin)
Clopidogrel (Plavix)
Aspirin