A long-used herbal drug taken to lower cholesterol may interfere with nearly 60 percent of all prescription drugs, including the popular anti-cholesterol drugs called statins, new research reports.

In a preliminary study, investigators found that the guggulsterone, the active ingredient in the herbal remedy gugulipid, causes changes in human and rodent cells that induce the body to break down many drugs, including cancer drugs and AIDS medications.

These findings demonstrate how important it is to inform your doctor of any herbal medicines you are taking, study author Dr. Jeff L. Staudinger of the University of Kansas in Lawrence told Reuters Health.

“People need to be careful about herbal medicines,” he said. “Because, in fact, they are drugs.”

Resin from the guggul tree has been used for more than 3,000 years in India to treat a range of disorders. Previous research showed that guggulsterone lowers cholesterol by blocking a substance that keeps the body from getting rid of cholesterol.

To investigate whether it is safe to take guggulsterone with prescription medicines, Staudinger and his colleagues examined the effects of guggulsterone on liver cells in laboratory experiments. Their findings appear in the Journal of Pharmacology and Experimental Therapeutics.

Staudinger suggested that guggulsterone likely affects other drugs because it binds to a protein known as pregnane X receptor (PXR). This, in turn, induces the body to “turn on” a gene that encodes another protein that breaks down many different types of drugs, thereby reducing their levels in the body, he noted.

Staudinger added that some anticancer drugs, such as cyclophosphamide, need to be broken down by PXR to become active. Guggulsterone may interfere by augmenting that process, thereby raising levels of the drugs in the body.

Moreover, guggulsterone appears to also turn some other drugs, such as acetaminophen, into toxic compounds.

He noted that another herbal remedy, St. John’s wort, also activates PXR, and can therefore interfere with other drugs. He recommends that all herbal extracts be screened to determine if they affect PXR.

However, Staudinger noted that guggulsterone has been used for years, and is likely safe if people are not taking any prescription medications. However, guggulsterone should be used cautiously by people who take prescription drugs, he said.

SOURCE: The Journal of Pharmacology and Experimental Therapeutics, August 2004.