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increase side effects such as nausea, anxiety, headache, and confusion. Using St. John’s
wort with MAOIs may also increase the risk of severely increased blood pressure.
Mischoulon and Rosenbaum report 17 cases of psychosis resulting from St. John’s
wort, of which 12 involved mania or hypomania, adding: "Clinicians should therefore
advise bipolar patients to use St. John’s wort only in combination with a mood
stabilizer."^20 People with bipolar illness who take St. John’s wort should be carefully
monitored, in view of the risk of cycling (speeding up the depression/mania cycle).
St. John’s wort can interact with birth control pills, but this interaction is controversial,
with three recent (2003-2008) studies finding no reduced contraceptive effect and two
showing lowered contraceptive efficacy.^21 The frequency of interaction is difficult to
estimate, and a sixth recent study describes it as "unpredictable." One report
mentioned eight cases of interaction, but the rate is unknown. In summary, there
appears to be a potential interaction that decreases biologic activity of oral
contraceptives, but this may vary depending on the birth control pill formulation and
the St. John’s wort formulation (hypericin or hyperforin content) and possibly other
factors. The studies are limited by small samples, but this is more than just anecdotal
evidence. How likely a woman is to become pregnant from this interaction remains
unclear, but there is enough evidence to warrant caution. There is a clear risk of
breakthrough bleeding from this interaction.
All of the sources urge caution in the use of St. John’s wort if ANY other medications are
being used. The list of additional potential drug interactions includes:
digoxin (digitalis) or digitoxin which strengthen heart muscle contractions
loperamide (Immodium) (Probably uncommon)
triptan-type headache medications such as naratriptan (Amerge), rizatritan (Maxalt),
COX-2 inhibitor drugs like rofecoxib (Vioxx) (Probably uncommon)
non-steroidal anti-inflammatory drugs like ibuprofen (Motrin) (Probably uncommon)
St. John’s wort has been shown to decrease the concentrations of imatinab,
omeprazole, tolbutamide, caffeine, dextromethorphan, fexofenadine, cimetidine,