There is a common perception among both the general public and the medical community that herbal medicines are safer than conventional drugs. This is not only incorrect, but a dangerous misconception that could cause risky drug interactions. A new study has shown that the naturally occurring Hypericum perforatum, better known as St. John’s Wort, causes some of the same adverse reactions as antidepressants, and when taken together, the two can create dangerous side effects.

Published in Clinical and Experimental Pharmacology and Physiology, the study consisted of comparing patterns of adverse reactions to both St. John’s Wort and fluoxetine, which is a common clinical antidepressant. Researchers looked at data from 2000 to 2013, and analyzed reports of spontaneous adverse reactions to both drugs. It was discovered that reactions to both drugs included anxiety, dizziness, vomiting, amnesia, aggression and panic attacks. They were also found to affect the same body systems, with the majority of reactions affecting the central nervous system.

"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,” said University of Adelaide pharmacology PhD student Claire Hoban in a press release. “People need to start thinking of St John's Wort, and other herbal medicines, as a drug and seek advice from a qualified healthcare practitioner to be sure they use it safely. It's concerning to see such severe adverse reactions in our population, when people believe they are doing something proactive for their health with little risk.

Researchers found 84 reports of adverse reactions to St. John’s Wort, and 447 to fluxotine.

“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,” Hoban said.

The study also highlighted the importance of avoiding drug interactions, since St. John’s Wort is easily accessible and does not require a prescription. There is no control over dosage or the drugs people may choose to take in conjunction with it.

Dr. Ian Musgrave, from the University’s Discipline of Pharmacology, felt that improved warning labels on bottles of St. John’s Wort would be beneficial.

"Most people taking St John's Wort will not have any adverse reactions; however, those who do take it should tell their doctor and pharmacist," said Dr. Musgrave said in a press release. “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.

Source: Hoban C, A Comparison of Patterns of Spontaneous Adverse Drug Reaction Reporting With St. John’s Wort and Fluoexotine During the Period 2000-2013. Clinical and Experimental Pharmacology and Physiology. 2015.