The usual dose of St. John's wort is 900mg/day (.3% hypericin/3-6% hyperforin
content), taken in divided doses. The clinical effect usually takes 2 to 3
weeks to appear. In some European countries, St. John's wort is registered
for the treatment of mild to moderate depression; in the United States, it is
marketed as a dietary supplement.
Taken as a monotherapy, St. John's wort has an excellent safety profile when
compared to standard prescribed medications in the treatment of depression.
In a drug monitoring study of 3,250 patients taking 900mg/day, adverse events
were reported in 2.4 percent of subjects, the most common being gastrointestinal
irritation, restlessness, fatigue, and allergic skin reactions.
There are several rare, but serious side effects known to be associated with
the use of St. John's wort including photosensitization, induction of mania in
patients with bipolar disorder, hypertensive crisis, and induction of hepatic
enzymes. Serotonin syndrome has been reported to occur with the
concomitant use of St. John's wort and selective serotonin reuptake inhibitors (SSRIs).
Research in humans has also shown that St. John's wort causes induction of the
cytochrome P450 isoenzyme CYP3A4, and may affect the metabolism of any drugs
metabolized via this enzyme system. Pharmacological studies have shown
that serum levels of the following drugs may be affected by St. John's wort:
indinavir, cyclosporine, theophylline, digoxin, warfarin, oral contraceptives,
simvastatin, pravastatin, omeprazole, irinotecan, tacrolimus, verapamil, and
methadone. Care should be taken in patients also using
benzodiazepines.
The use of St. John's wort during pregnancy and breastfeeding has been poorly
studied. A 2003 study published in the Journal of Clinical Psychiatry
examined the safety of St. John's wort during breastfeeding. This study
reported no decrease in maternal milk production and no differences in infant
weight or growth. However, the study did note that women receiving St.
John's wort reported a higher incidence of subjective adverse events in their
infants, although none of the infants required any medical intervention.
It is highly recommended that you notify your physician before taking St. John's wort
in order to avoid any serious complications or drug-drug interactions. |
