En excerpt from the book : 

"ALTERNATIVES IN CANCER THERAPY"
  by Ross, R.Ph. Pelton, Lee Overholser

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Pau d'arco 

FOR CENTURIES the Indians of the Amazon jungles have made tea from the inner bark of trees of the Tabebuia genus (also called Lapacho}. The tea is called pau d'arco, from the Spanish for "bow stick," the Indian name for the tree, because they use its wood to make bows. The Guarani and Tupi-Nambo Indian tribes still use the plant for a variety of diseases, including cancer.

Bacround

The preparation initially came to the attention of scientists because of its antimalarial properties. (7) Then in the early 1960s a girl from Sao Paulo, Brazil, was treated for cancer by an aunt who had been given a small bag of bark from the pau d'arco tree by an Indian medicine man. The girl was in considerable pain and had been declared unbeatable, but the tea apparently cured her cancer.

A friend of the family, Dr. Orlando dei Santi, heard of the cure and brought some of the bark back to Sao Paulo to treat his brother, who was also suffering from inoperable, terminal cancer. The doctor administered a brew made by boiling the bark in white wine, mixing it with orange juice, and having his brother drink the resulting concoction on an empty stomach. Once again there appeared to be a rapid and remarkable cure. (4)

Another South American physician, Dr. Prats Ruiz, reported that he had successfully treated three cases of leukemia with pau d'arco tea in the mid-1960s. In one case a five-year-old girl was terminally ill with leukemia; after two months of treatment with the herbal preparation, her blood count returned to normal. (5)

It was anecdotal reports like these that led researchers to attempt to isolate the active ingredient in pau d'arco tea and conduct clinical tests.

Mechanism of Action

The story of pau d'arco tea is typical of the fate of many promising natural treatments for cancer. Based on stories of successful treatments, researchers test the plant extract on strains of cancer cells in the laboratory or in vitro. Then, if the tests are promising, they attempt to extract the active ingredient responsible for killing the cancer cells.

One difficulty with this process is that the plant may contain several compounds that act together to produce the desired results. Also, there may be constituents that modify the effect of the toxic active ingredient on living organisms.

Researchers then test the active ingredient in test animals, usually mice that are bred to be highly susceptible to the development of one form of cancer or another, usually leukemia and skin or breast cancer. If these tests generate positive results, then the compound is tested on human volunteers, and its use is refined to minimize any toxic side effects that may be revealed.

In the late 1960s researchers isolated a compound called la-pachone from the bark of the pau d'arco tree, or Tabebuia cas-sinoides. (14) They realized that this is the same substance as that studied earlier for antimalarial properties. Lapachone is generally called lapachol.

Lapachol is a quinone like NDGA, the active extract of chaparral. Studies show that lapachol and several similar qui-nones reduce the biological activity of cancer cells. (10) Lapachol showed activity against leukemia cells in early tests and was effective enough in animal experiments to call for clinical trials. (16)

Dr. Rao found that the molecular makeup of lapachol has a structure that is uniquely suited to strong biologic activity against cancer. (15) Other researchers proposed that lapachol has the effect of interfering with normal cellular energy production and normal cellular respiration. (8, 9) This is particularly damaging to cancer cells because of their enormous rates of growth and reproduction. Take away their energy source, and they wither and die.

Another study determined that a variant of the original drug, called beta-lapachone, increased the effectiveness of X rays on cancer cells by preventing the cancer cells from repairing their damaged DNA. (2, 3) Lapachol does not have this effect.

In the late 1970s two researchers produced other variants of lapachol, by fermenting it with bacteria, Penicillium notatum (11) and Curvularia lunata. (12) These fermentation products showed considerable biological activity, and one in particular, dehydro-alpha-lapachone, showed antitumor effects. (6, 7)

Clinical Trials

Based on studies, in 1974 with rats, that showed significant effects on tumors, especially when the drug was administered orally, lapachone was approved for trials with humans. (14) The drug was administered twice daily, and it showed relatively mild signs of general toxicity.

Early clinical studies showed that lapachol is well tolerated in humans, causing nausea, vomiting, and slow clotting only at very high oral doses. (1) The research was stopped because of the anticlotting effect of lapachol and the fact that blood levels of lapachol high enough to attack the tumors could be reached only by giving such high doses that the subjects became sick. It appears that higher doses were required in human subjects because people absorb the drug less efficiently in the intestines than test animals do. Other means of administration may be more effective.

The anticlotting effect of lapachol seems to be due to its similarity in structure to vitamin K. Vitamin K promotes clotting and prevents hemorrhaging. (17) A study of the effects of lapachol on rats confirmed that lapachol interferes with the metabolism of vitamin K. (13)

The final chapter in this story began in late 1974, when the National Cancer Institute branded pau d'arco tea an "unproved treatment," based on its anticlotting effect. This label is effectively

the same as calling a treatment a quack cure and brings research to a halt. Any researcher wishing to get funding avoids the taint of quackery like the plague. Related compounds are being investigated, but lapachol and pau d'arco have been relegated to the trash can, as far as the cancer establishment is concerned.

Dosage and Side Effects

A safe dosage of lapachol has not been determined because of the anemia and slowed clotting that it produces. The natural form, pau d'arco tea, appears to have no severe side effects. Of course the tea has not been studied extensively, and taking large doses or ingesting the bark in tablet form may produce the same negative effects that the extract lapachol has.

Treatment consists of taking 1 or more 8-ounce glasses of pau d'arco tea a day. At this point there is no clear evidence that this dosage level is therapeutically effective, and stronger doses may produce side effects. Anyone interested in using this treatment should consult an experienced physician or herbalist for further guidance.

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