Australasian Science: Australia's authority on science since 1938

Warning over Herbal Medicine Side-Effects

St John’s wort, a herbal treatment for depression, can produce the same adverse reactions as the antidepressant fluoxetine, with potentially serious side-effects when the two are taken together, according to a study published in Clinical and Experimental Pharmacology and Physiology.

University of Adelaide PhD student Claire Hoban says St John’s wort, like all herbal medicines, is a drug that can cause dangerous increases in body temperature and blood pressure. “There is a common belief that because something is natural and can be purchased from a health food shop without a prescription, it’s safe,” she said.

“During 2000–13, we found 84 reports of adverse reactions to St John’s wort and 447 to fluoxetine. While there were fewer confirmed cases of side-effects for St John’s wort, we know that less people use St John’s wort and adverse reactions for herbal medicines largely go unreported because they are not considered drugs.

“Furthermore, we found that the reported reactions for St John’s wort were very similar to fluoxetine, which included anxiety, panic attacks, dizziness, vomiting, amnesia and aggression,” she says.

Dr Ian Musgrave from the University’s Discipline of Pharmacology says the real danger is that people can access St John’s wort without a prescription, so there is no control over the dosage or what drugs people are using it with. “It’s important that doctors and pharmacists know about all the drugs their patients take, not just prescription drugs, because herbal medicines like St John’s wort can have serious reactions with some pharmacy medicines, like anti­depressants, the contraceptive pill and some blood thinners.

“Based on this research, I’d also like to see bottles of St John’s wort containing improved warnings of the potential adverse reactions,” he said.