- Indications with possible efficacy:
Depression - mild or moderate (popular use)
- Indications with possible, but poorly documented efficacy:
Nervous states, anxiety
- Indications with no proof of efficacy:
HIV infection and hepatitis C
- Risk of Drug Interactions: Important
- Adverse Effects: Not Frequent
Part of the plant used: leaves and flowers
The medicinal virtues of St John's wort have been appreciated for centuries and many uses have been proposed over time. St John's wort is indigenous to North America, Europe and Australia. It has very characteristic and pretty yellow star-shaped flowers. Although hypericin was thought to be the component responsible for St John's wort antidepressant activities, it is now understood that hyperforin and other related compounds are the primary active constituents. St John's wort is available in capsules, tablets or liquid extracts. Products are standardized to 0.3% hypericin or 3 to 5% hyperforin.
The antidepressant activity of St John's wort may be the result of a decrease in the synaptosomal reuptake of serotonin, norepinephrine and dopamine. In addition, an enzyme called monoamine oxydase (MAO) is inhibited, but this effect is weak. Other mechanisms involving other cerebral substances may also be in cause.
Direction of use
- Mild or moderate depression:
Used doses: 300 mg of standardized extract 3 times a day, with meals. The antidepressant effect takes a few weeks to develop. The recommended maintenance dose is 300 to 600 mg per day.
There is insufficient reliable information to conclude that St John's wort is effective in any other indication. The effect of hypericin on HIV, the virus responsible for AIDS, is under investigation. It has already been established that the oral form is not effective against HIV.
- Side effects
For most people, St. John's wort is not seriously toxic. Some people may, however, experience fatigue, gastro-intestinal upset, insomnia, restlessness, anxiety, irritability, dry mouth, dizziness, headache, and a delayed allergy or reaction to the sun. It may also cause sexual dysfunction. Its effect as a monoamine oxidase (MAO) inhibitor could caused serious undesirable reactions in the case of certain individuals after eating food rich in tyramine (example: certain aged cheeses and red wines). But this effect is weak and the real risk has not been determined.
Patients with bipolar disorder, schizophrenia, major depression or Alzheimer's disease should avoid St. John's wort. Avoid if liver diseases.
St. John's wort may reduce efficacy of cyclosporine (Neoral), digoxin (Lanoxin), tacrolimus (Prograf), theophylline, nifedipine (Adalat), some drugs against HIV, some drugs againt cancer, oral contraceptives or anticoagulants (Coumadin, Sintrom). St. John's wort can increase the adverse reactions of sibutramine (Meridia) and some antidepressants causing nausea, fever, shaking, agitation, dizziness, palpitations, and confusion. It could also increase the toxicity of volatile anesthetics used in surgery. The sedative effect of narcotics may be accentuated by St. John's wort. On the other hand, the sedative effect of barbiturates may be reduced. If you are already taking medication, check with your pharmacist to see if it is compatible with St. John's wort before using this product.
- Pregnancy and lactation
This product may be teratogenic and should be avoided during pregnancy. Its use during breasteeding is not contraindicated, but it is not a first-line agent. It is recommended to watch for signs of sedation in children exposed, especially in neonates (less than 2 months).
- St John's wort is a very popular natural remedy and is probably one of the most studied medicinal plant. To avoid adverse withdrawal effects, St John's wort dosages should be decreased gradually in 1 or 2 weeks.
In 2004, Canada adopted new regulations that control the manufacturing, packaging, labeling and importing of natural health products. The new regulations also include an adverse reaction reporting system. Products that conform to the regulation's criteria are identified with a natural product number (NPN) and can be legally sold in Canada. This number indicates that the product meets specific criteria for safety and purity, not that it is effective for any indication.
Medicinal plant contents vary naturally from plant to plant - just as fruits from the same package may vary in taste and texture. There is no standard to measure the active content of each plant. Thus, efficacy of natural products should be expected to vary from brand to brand as well as from bottle to bottle of the same brand.
For more information about the Natural Health Products Regulations, or to check if a product has been assessed, visit the Health Canada website at www.hc-sc.gc.ca/dhp-mps/prodnatur/index-eng.php.
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The patient information leaflets are provided by Vigilance Santé Inc. This content is for information purposes only and does not in any manner whatsoever replace the opinion or advice of your health care professional. Always consult a health care professional before making a decision about your medication or treatment.