St. John's Wort Extract – Effects, Uses and Dosage
St. John's wort extract is derived from the medicinal plant Hypericum perforatum and is traditionally used for mild depression and inner restlessness.
Things worth knowing about "St. John's Wort Extract"
St. John's wort extract is derived from the medicinal plant Hypericum perforatum and is traditionally used for mild depression and inner restlessness.
What is St. John's Wort Extract?
St. John's wort extract is a herbal active substance obtained from the flowers and leaves of the common St. John's wort plant (Hypericum perforatum). The plant belongs to the Hypericaceae family and is native to Europe, Asia, and North Africa. For centuries, it has been used in traditional herbal medicine to treat low mood, nervousness, and sleep disturbances. Today, standardised St. John's wort extract is one of the best-selling herbal medicinal products in Europe.
Active Compounds and Mechanism of Action
The pharmacological effects of St. John's wort extract are attributed to several bioactive compounds:
- Hypericin and pseudohypericin: Naphthodianthrone derivatives that serve as quality markers for standardised extracts and are believed to contribute to antidepressant activity.
- Hyperforin: Currently considered the key active compound. It inhibits the reuptake of serotonin, dopamine, noradrenaline, GABA, and glutamate into nerve cells, producing a mood-lifting effect.
- Flavonoids (e.g., rutin, quercetin, amentoflavone): Possess antioxidant and anti-inflammatory properties and contribute to the overall therapeutic effect.
The exact mechanism of action is not yet fully understood; however, the action of hyperforin resembles that of selective serotonin reuptake inhibitors (SSRIs), without acting exclusively on a single neurotransmitter system.
Medical Applications
St. John's wort extract is used in phytotherapy and conventional medicine for the following indications:
- Mild to moderate depression: This is the best-supported indication. Multiple clinical studies and meta-analyses show that standardised extract may be effective in mild to moderate depressive episodes, with fewer side effects than synthetic antidepressants.
- Inner restlessness and nervousness: Traditionally used for nervous tension and irritability.
- Seasonal affective disorder (SAD): Initial evidence suggests effectiveness for seasonal low mood, often in combination with light therapy.
- Mild sleep disturbances: Due to the mildly sedating properties of certain constituents.
Dosage and Usage
For a therapeutic effect, the use of standardised extracts is essential. The recommended daily dose for standardised extracts (0.3% hypericin, 3-5% hyperforin) is generally 300 mg to 900 mg per day, divided into 2-3 doses. The full therapeutic effect often only appears after 4-6 weeks of regular use. St. John's wort extract is available as capsules, tablets, film-coated tablets, and tea.
Side Effects
St. John's wort extract is generally well tolerated, but may cause the following side effects:
- Photosensitisation: Increased sensitivity of the skin to light, especially in fair-skinned individuals and at higher doses. Intense sun exposure and tanning beds should be avoided during use.
- Gastrointestinal complaints such as nausea or stomach discomfort
- Dry mouth and dizziness (rare)
- Fatigue or restlessness (varies between individuals)
Drug Interactions
A critical aspect of using St. John's wort extract is its clinically significant interactions with numerous medications. Hyperforin is a potent inducer of the cytochrome P450 enzyme system (CYP3A4) and P-glycoprotein, which accelerates the breakdown of many drugs and may reduce their effectiveness:
- Anticoagulants (e.g., warfarin, phenprocoumon): Reduced anticoagulant effect
- Hormonal contraceptives (the pill): Reduced contraceptive reliability, risk of unintended pregnancy
- Immunosuppressants (e.g., ciclosporin): Significant loss of effect, particularly relevant in organ transplant patients
- Antiretroviral drugs (HIV therapy): Reduced efficacy
- Antidepressants (SSRIs, MAO inhibitors): Risk of serotonin syndrome if used simultaneously
- Cardiac glycosides, chemotherapy agents, antiepileptics
Due to these interactions, St. John's wort extract should not be taken without consulting a doctor or pharmacist, especially when other medications are being used.
Safety and Contraindications
St. John's wort extract should not be used, or only used after medical consultation, in the following situations:
- Severe depression (psychiatric treatment is required)
- Pregnancy and breastfeeding (insufficient data)
- Children under 12 years of age
- Concurrent use of medications with known interactions
References
- Linde K. et al. - St John's wort for major depression. Cochrane Database of Systematic Reviews, 2008.
- European Medicines Agency (EMA) - Assessment report on Hypericum perforatum L., herba. EMA/HMPC/101303/2013.
- National Institutes of Health (NIH), National Center for Complementary and Integrative Health - St. John's Wort and Depression: In Depth. www.nccih.nih.gov.
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