St John's wort

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It works in depression, but interacts with other drugs making polypharmacy a bad idea.

The flowering tops of St. John's wort (Hypericum perforatum) are used to prepare concentrated extracts. The active ingredients are thought to be hypericin and hyperforin, but this is difficult to be certain about as the herb contains several organic compounds. As there is no standardisation of herbal medicines production, St John's wort is usually sold by hypericin content, though the proportion of other ingredients is often not stated. The lack of a clear active ingredient makes studying the pharmacology difficult, but it is thought to act in a mechanism similar to SSRIs.

A Cochrane Systematic Review [1] reported that the current evidence was “inconsistent and confusing”

The American National Center for Complementary and Alternative Medicine (part of the National Institute for Health) has a fact sheet on St John's Wort [2]. They report that there is some evidence for the use St. John’s Wort is useful for treating mild to moderate depression. However, two large studies (one sponsored by them), have shown no effectiveness in major depression of moderate severity.[3]

See also: Evidence-Based Mental Health “Review: St John’s Wort may be less effective than previously thought in people with depression” [4]

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The MHRA issued in February 2016 a recall notice of multiple batches widely marketed since 2013. At this time no hepatotoxicity due to presumed isolated episodes of contamination during harvesting has been reported.

Side effects

Taken from the National Center for Complementary and Alternative Medicine fact sheet [5]

St. John's wort can cause increased sensitivity to sunlight. Other side effects can include dry mouth, anxiety, dizziness, gastrointestinal symptoms, fatigue, headache, or sexual dysfunction.[6]

The herb affects the way the body processes or breaks down many drugs; in some cases, it may speed or slow a drug's breakdown. Drugs that can be affected include:

St John's Wort is named for its date of flowering but may be more than one species of Hypericum

When combined with some antidepressants, St. John's wort can increase side effects.