Series by Kathleen Kendall-Tackett, Ph.D. (St. John’s Wort #3)

This is the third article in a five-part series on St. John’s Wort, an herb with antidepressant properties. 





Part 3, Safety Concerns

Safety Concerns

Taken by itself, St. John’s wort has an excellent safety record, with a very low frequency of adverse reactions (Ernst, 2002; Humphrey, 2003; Muller, 2003).  Approximately 2.4% of patients who take St. John’s wort develop side effects.  The most common are mild stomach discomfort, allergic reactions, skin rashes, tiredness, and restlessness.  Like other antidepressants, St. John’s wort can trigger an episode of mania in vulnerable patients or patients with bipolar disorder (Bratman & Girman, 2003).  St. John’s wort can also cause photosensitivity.  A review of 38 controlled clinical trials and two meta-analyses on St. John’s wort found its safety and side-effect profile to be better than standard antidepressants.  The incidence of adverse events ranged from 0% to 6%, which is 10 times less than adverse effects associated with antidepressants (Schultz, 2006).


More concerning is that St. John’s wort interacts with several classes of medications and accelerates the metabolism of anticonvulsants, cyclosporins, birth control pills, and others, leading to lower serum levels of the medication than prescribed (Duguoa et al., 2006; Ernst, 2002; Hale, 2006).   It can also interact with prescription antidepressants, causing a potentially fatal episode of serotonin syndrome (Bratman & Girman, 2003; Looper, 2007; Werneke et al., 2006).  Prescription antidepressants should not be taken while taking St. John’s wort (Harkness & Bratman, 2003).  Any mothers who are taking St. John’s wort need to tell their health care providers that they are taking it.  The medications that St. John’s wort interacts with are listed in Table 11.

Table 11: Cautions about Drug Interactions with St. John’s Wort


St. John’s wort 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:


·         Indinavir and possibly other drugs used to control HIV infection

·         Irinotecan and possibly other drugs used to treat cancer

·         Cyclosporine, which prevents the body from rejecting transplanted organs

·         Digoxin, which strengthens heart muscle contractions

·         Warfarin and related anticoagulants

·         Birth control pills

·         Antidepressants


Source: National Center for Complementary & Alternative Medicine (


Be sure to read tomorrow’s post,


Part 4, St. John’s Wort and Breastfeeding


 Part 5, Summary and references








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