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St. John’s Wort
Common name: Klamath weed
Botanical name: Hypericum perforatum
© Steven Foster
Parts used and where grown
St. John’s wort is found in Europe and the United States. It is especially abundant in northern California and southern Oregon. The above-ground (aerial) parts of the plant are gathered during the flowering season.
St. John’s wort has been used in connection with the following conditions (refer to the individual health concern for complete information):
| Science Ratings | Health Concerns |
|---|---|
 |
Depression Eczema (topical application) Seasonal affective disorder Somatoform disorders |
 |
Anxiety Cold sores Ear infections (recurrent) HIV support Infection Menopause Ulcerative colitis Wound healing |
 Reliable
and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies
suggesting a health benefit or minimal health benefit. For an herb, supported by traditional use but minimal
or no scientific evidence. For a supplement, little scientific support and/or minimal health
benefit. |
|
Historical or traditional use (may or may not be supported by scientific studies)
In ancient Greece, St. John’s wort was used to treat many ailments, including sciatica and poisonous reptile bites. In Europe, St. John’s wort was used by herbalists for the topical treatment of wounds and burns. It is also a folk remedy for kidney and lung ailments as well as for depression.
Active constituents
The major constituents in St. John’s wort include hypericin and other dianthrones, flavonoids, xanthones, and hyperforin.1 While it was previously thought the antidepressant actions of St. John’s wort were due to hypericin and the inhibition of the enzyme monoamine oxidase,2 current research has challenged this belief, focusing on other constituents, such as hyperforin, and flavonoids.3 4 5 Test tube studies suggest that St. John’s wort extracts may exert their antidepressant actions by inhibiting the reuptake of the neurotransmitters serotonin, norepinephrine, and dopamine.6 This action is possibly due to the constituent hyperforin.7 St. John’s wort is able to act as an antidepressant, by making more of these neurotransmitters available to the brain.
How much is usually taken?
The standard recommendation for mild to moderate depression is 500–1,050 mg of St. John’s wort extract per day.8 9 10 Results may be noted as early as two weeks. Length of use should be discussed with a healthcare professional. For more severe depression, higher intakes may be used, under the supervision of a healthcare professional.
Are there any side effects or interactions?
St. John’s wort has a low incidence of side effects compared to prescription antidepressants. An adverse events profile of St. John’s wort found that, of 14 controlled clinical trials, seven reported no adverse reactions, two had no information, and five reported a total of seven mild reactions.11 Adverse effects reported included stomach upset, fatigue, itching, sleep disturbance, and skin rash. The rate of adverse reactions was always similar to that of the placebo. Additionally, in seven trials comparing St. John’s wort with other antidepressants, the adverse reaction rate for St. John’s wort was consistently lower than that of the antidepressant drugs with which it was compared.
St. John’s wort can make the skin more sensitive to sunlight.12 Therefore, fair-skinned people should be alert for any rashes or burns following exposure to the sun. Three cases of severe blistering and burns were reported in people taking St. John’s wort internally or applying it topically and then being exposed to sunlight.13 There is a case report of a woman experiencing neuropathy (nerve injury and pain) in sun-exposed skin areas after taking 500 mg of whole St. John’s wort for four weeks.14 Although St. John’s wort has photosensitizing properties, the severity of this reaction is not typical for people taking the herb.
People with a history of manic-depressive illness (bipolar disorder) or a less severe condition known as hypomania, should avoid use of St. John’s wort as it may trigger a manic episode.15 16 17 18
There is a single case report in which ingestion of St. John's wort appeared to cause high blood pressure in a 56-year-old man. The blood pressure returned to normal when the herb was discontinued.19
Are there any drug
interactions?
Certain medicines may interact with St. John’s wort. Refer to drug interactions for a list of those medicines.
Caution: It is likely that there are many drug interactions with St. John's wort that have not yet been identified. St. John's wort stimulates a drug-metabolizing enzyme (cytochrome P450 3A4) that metabolizes at least 50% of the drugs on the market.20 Consequently, St. John's wort could potentially interfere with a large number of medications. Individuals taking any medication should, therefore, consult with a physician before taking St. John's wort.
References
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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires September 2008.