SAN DIEGO -- Herbal supplements may be natural, but that doesn't necessarily mean they're safe.

Drug interactions between herbal and prescription medicines can be extremely dangerous, according to the World Health Organization.

"It's something we've been concerned about in the pharmacy industry -- how we combat drug interactions," said Dr. Charles James, an infectious diseases specialist at University of California, San Diego.

Although much of the research is still preliminary, recent studies have highlighted the dangers of combining prescription drugs with herbal remedies.

Julie Plunkett, a nutritionist and herbalist, said, "(Herbal supplements) have effective medicinal action and should be used with the same respect and responsibility as over-the-counter drugs."

Commonly prescribed blood thinners and HIV medications can interact with St. John's Wort or other herbal medications. And if a patient takes St. John's Wort in combination with birth control pills, the birth control pills may not be as effective. Even some potent vitamins can interact with antibiotics if taken together, according to WHO.

"It's just not appropriate to be treating simultaneously. We recommend a person use herbs or medications," Plunkett said.

Plunkett believes warning labels are necessary. Some drug companies already list herbal interactions.

Bayer, which makes the antibiotic Cipro, warns users to stay away from calcium-fortified orange juice and other calcium products, but the warning is written in very small print.

"It has to be readable and approachable by the general public," Plunkett said.

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