St. John’s Wort
Common name: Klamath weed
Botanical name: Hypericum perforatum
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):
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
Science Ratings
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 a 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, fairskinned 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.
Drug Interactions
Certain medicines interact with St. John’s wort: Some interactions may increase
the need for St. John’s wort ( ), other interactions may be negative ( ) and
indicate St. John’s wort should not be taken without first speaking with your
physician or chemist, others may require further explanation ( ). Refer to the
individual drug article for specific details about an interaction.
Note: The following list only includes the generic or class name of a medicine. To
find a specific brand name, use the Medicines index.
Atazanavir
Benzodiazepines
Chemotherapy
Cyclosporine
Digoxin
Fexofenadin
Fluoxetine
Fluvoxamine
Fosamprenavir
HMG-CoA Reductase Inhibitors (Statins)
Indinavir
Nefazodone
Omeprazole
Oral Contraceptives
Paroxetine
Phenelzine
Sertraline
Theophyline/Aminophiline
Trazodone
Atazanivir Tricyclic Antidepressants
Venlafaxine
Warfarin
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-metabolising
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
1. Gruenwald J. Standardized St. John’s wort clinical monograph. Quart Rev Nat
Med 1997;Winter:289–99.
2. Suzuki O, Katsumata Y, Oya M. Inhibition of monoamine oxidase by hypericin.
Planta Med 1984;50:272–4.
3. Holzl J, Demisch L, Gollnik B. Investigations about antidepressive and mood
changing effects of Hypericum perforatum. Planta Med 1989;55:643.
4. Chatterjee SS, Koch E, Noldner M, et al. Hyperforin with hypericum extract:
Interactions with some neurotransmitter systems. Quart Rev Nat Med
1997;Summer:110.
5. Calapai G, Crupi A, Firenzuoli F, et al. Effects of Hypericum perforatum on
levels of 5-hydroxytryptamine, noradrenaline and dopamine in the cortex,
diencephalon and brainstem of the rat. J Pharm Pharmacol 1999;51:723–8.
6. Müller WE, Rolli M, Schäfer C, Hafner U. Effects of hypericum extract (LI 160)
in biochemical models of antidepressant activity. Pharmacopsychiatry
1997;30(suppl):102–7.
7. Müller WE, Singer A, Wonnemann M, et al. Hyperforin represents the
neurotransmitter reuptake inhibiting constituent of hypericum extract.
Pharmacopsychiatry 1998;31(suppl):16–21.
8. Brown DJ. Herbal Prescriptions for Better Health. Rocklin, CA: Prima
Publishing, 1996, 159–65.
9. Woelk H. Comparison of St. John’s wort and imipramine for treating
depression: Randomized controlled trial. BMJ 2000;321:536–9.
10. Philipp M, Kohnen R, Hiller KO. Hypericum extract versus imipramine or
placebo in patients with moderate depression: randomized multicenter study of
treatment for eight weeks. BMJ 1999;319:1534–9.
11. Ernst E, Rand JI, Barnes J, et al. Adverse effects profile of the herbal
antidepressant St. John’s wort (Hypericum perforatum L.) Eur J Clin Pharmacol
1998;54:589–94.
12. Brockmöller J, Reum T, Bauer S, et al. Hypericin and pseudohypericin:
Pharmacokinetics and effects on photosensitivity in humans. Pharmacopsychiatry
1997;30(suppl):94–101.
13. Lane-Brown MM. Photosensitivity associated with herbal preparations of St.
John’s wort (Hypericum perforatum). MJA 2000;172:302[Letter].
14. Bove GM. Acute neuropathy after exposure to sun in a patient treated with St
John’s Wort. Lancet 1998;352:1121–2 [letter].
15. Nierenberg AA, Burt T, Matthews J, Weiss AP. Mania associated with St.
John’s wort. Biol Psychiatry 1999;46:1707–8.
16. Moses EL, Mallinger AG. St. John’s wort: Three cases of possible mania
induction. J Clin Psychopharmacol 2000;20:115–7.
17. O’Breasail AM, Argouarch S. Hypomania and St John’s wort. Can J Psychiatry
1998;43:746–7 [letter].
18. Schneck C. St. John’s wort and hypomania. J Clin Psychiatry 1998;59:689
[letter].
19. Zullino D, Borgeat F. Hypertension induced by St. John's Wort: a case report.
Pharmacopsychiatry. 2003;36:32.
20. Markowitz JS, Donovan JL, DeVane CL, et al. Effect of St John's wort on drug
metabolism by induction of cytochrome P450 3A4 enzyme. JAMA
2003;290:1500–4.
St. John’s Wort for Weight Control
Why do dieters use it?*
Some dieters say that St. John’s wort


helps improve energy and alertness.
helps relieve stress and anxiety.
What do the advocates say?*
St. John’s wort is well established as a remedy for mild to moderate depression.
Since depression can lead to weight gain, and since medications with actions
similar to that of St. John’s wort have been used for weight loss, some people
have proposed that St. John’s wort can be useful for weight loss. However, no
research at all has investigated whether St. John’s wort has any value for this
purpose.
How much is usually taken by dieters?
The standard recommendation for mild to moderate depression is 500 to 1,050
mg of St. John’s wort extract per day.1 2 3 Length of use should be discussed with
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.4 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. 5 Therefore, fairskinned 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. 6
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.7 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.8 9 10 11
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.12
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-metabolising
enzyme (cytochrome P450 3A4) that metabolizes at least 50% of the drugs on
the market.13 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.
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.
Resources
See a list of books, periodicals, and other resources for this and related topics.
*Dieters and weight-management advocates may claim benefits for St. John’s
wort based on their personal or professional experience. These are individual
opinions and testimonials that may or may not be supported by controlled clinical
studies or published scientific articles on St. John’s wort. For more complete and
detailed information, including references and safety information, see St. John's
Wort as an herbal remedy .
References
1. Brown DJ. Herbal Prescriptions for Better Health. Rocklin, CA: Prima
Publishing, 1996, 159–65.
2. Woelk H. Comparison of St. John’s wort and imipramine for treating
depression: Randomized controlled trial. BMJ 2000;321:536–9.
3. Philipp M, Kohnen R, Hiller KO. Hypericum extract versus imipramine or
placebo in patients with moderate depression: randomized multicenter study of
treatment for eight weeks. BMJ 1999;319:1534–9.
4. Ernst E, Rand JI, Barnes J, et al. Adverse effects profile of the herbal
antidepressant St. John’s wort (Hypericum perforatum L.) Eur J Clin Pharmacol
1998;54:589–94.
5. Brockmöller J, Reum T, Bauer S, et al. Hypericin and pseudohypericin:
Pharmacokinetics and effects on photosensitivity in humans. Pharmacopsychiatry
1997;30(suppl):94–101.
6. Lane-Brown MM. Photosensitivity associated with herbal preparations of St.
John’s wort (Hypericum perforatum). MJA 2000;172:302[Letter].
7. Bove GM. Acute neuropathy after exposure to sun in a patient treated with St
John’s Wort. Lancet 1998;352:1121–2 [letter].
8. Nierenberg AA, Burt T, Matthews J, Weiss AP. Mania associated with St. John’s
wort. Biol Psychiatry 1999;46:1707–8.
9. Moses EL, Mallinger AG. St. John’s wort: Three cases of possible mania
induction. J Clin Psychopharmacol 2000;20:115–7.
10. O’Breasail AM, Argouarch S. Hypomania and St John’s wort. Can J Psychiatry
1998;43:746–7 [letter].
11. Schneck C. St. John’s wort and hypomania. J Clin Psychiatry 1998;59:689
[letter].
12. Zullino D, Borgeat F. Hypertension induced by St. John's Wort: a case report.
Pharmacopsychiatry. 2003;36:32.
13. Markowitz JS, Donovan JL, DeVane CL, et al. Effect of St John's wort on drug
metabolism by induction of cytochrome P450 3A4 enzyme. JAMA
2003;290:1500–4.