Herbs and Drugs: Are They Safe?

| May/June 2000

A recent story in a Denver, Colorado, newspaper carried this ominous headline: “Herbal remedy rapped, cancels chemo, researcher says.” According to a pharmacologist at the University of Colorado’s Health Sciences Center, studies in his laboratory showed that hypericin, one of the active ingredients in St. John’s wort (Hypericum perforatum), had been found to interfere with the action of etoposide, a chemotherapy agent used in the treatment of lung, ovarian, and testicular cancer. Ironically, etoposide has its roots in herbal medicine—it’s a synthetic derivative of podophyllin, an extract from mayapple root (Podophyllum peltatum).

Etoposide appears to work by inhibiting an enzyme called topoisomerase II that cancer cells use for repairing their DNA, which in turn allows them to divide rapidly. Inhibiting this enzyme keeps the cancer cells from dividing, thus slowing the growth of the cancer. Through a complex mechanism, hypericin seems to prevent etoposide from achieving this effect. Other than blocking the drug’s action, no negative effects of hypericin were found. There was also no implication that hypericin would cancel out the effect of chemotherapy agents that worked by a different mechanism.

However, based on this finding, the article goes on to state that “the interaction is just one more sign that herbal remedies should be looked upon as medications by the FDA and not as mere supplements.”

While I agree that the laboratory findings may be cause for concern, I do not understand how they lead to the assertion that herbs should be regulated as drugs.

Questions About the Study:

Two questions are left unanswered by the article, questions that should always be asked when a potential herb/drug interaction has been identified.

First of all, is the concentration of the herbal extract similar to what would be achieved in the bloodstream when a person takes the herb in a normal daily dose? Typically, laboratory studies use isolated compounds in high concentrations that may not reflect what occurs in an actual clinical situation. For example, this study looked at pure hypericin, whereas most commercial St. John’s wort products contain only 0.3 percent hypericin, a relatively low concentration.

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