St John's Wort - Hypericum perforatum
This information explains what St John's wort is used for, how it works, possible side effects and interactions with other medicines.
About St John's Wort
What is St John's wort?
St John's wort (pronounced to rhyme with ’skirt’) is a herb that has been used as a folk medicine for hundreds of years, for mental health problems and for healing wounds. Today, it is mainly used for depression, mild anxiety, and sleep problems.
Its botanical name is Hypericum perforatum, and you may see it marketed as ‘Hypericum’ (this comes from the Greek, meaning 'greatest health'). The active ingredient for depression is called hypericin, and when you buy it, the packaging should tell you the amount of hypericin, or ‘hypericum extract’, in each tablet or capsule.
It also contains hyperforin which has antibiotic properties.
How it works
Research suggests that it increases the activity and prolongs the action of the brain chemicals serotonin and noradrenaline, in a similar manner to standard antidepressants, but with far fewer reported side effects.
Tablets made using a standardised extract of St John's wort, to treat depression, have been extensively researched in Germany since the early 1980s, and were found to be effective for mild to moderate depression.
Research in America found it unhelpful for severe depression, but this has been questioned by more recent research which suggested that it was comparable with paroxetine (a synthesised antidepressant) in moderate to severe depression.
Depending on the herbal composition of the product used, St John's wort may take effect more quickly than prescribed antidepressants. (See Making sense of antidepressants.)
In addition to hypericin and hyperforin mentioned above, the plant contains many other substances which may contribute to its antidepressant activity in ways that are not yet understood.
How it is taken
What form does it take?
St John’s wort can be taken as tablets and capsules, and you can also get it as a tea, and as a liquid called a tincture, which you could take as drops in water.
There are other products available that combine St John's wort with other herbs, such as lemon balm (Melissa officianalis) and hops (Humulus lupulus), which are both good for sleep. This combination would be suggested for people with depression who have difficulty sleeping.
I found that just taking the tea form of St John’s wort was very helpful for me in alleviating the symptoms of depression … I think it might depend on the individual as to what form of the herb helps best and the dose.
What dosage should I take?
The different forms of St John’s wort vary in dosage, which is not standardised. The research trials done in Germany (see How does it work?) seem to have used a daily dose of total extract, ranging from 0.4mg (400 micrograms) up to 1,000mg (1 gram).
Preparations available in the UK often give a strength in terms of percentage of hypericin, or hypericum extract, and the suggested dosage is 200mg to 1,000mg of 0.3 per cent standardised hypericum extract per day, which is usually taken in two or three doses.
As the amount of active ingredient varies between preparations, you need to read the packaging carefully to see what dose you should be taking. It’s easiest to be sure of the dosage if you take the tablets or capsules, and stick to one particular brand. Be aware that if you buy a different type or brand, the dosage may be different.
Safety and side effects
Is it always safe to take St John's wort?
Many people believe that as herbal remedies are 'natural', they are completely safe and free of side effects. This is not the case: many herbs are poisonous if used in the wrong way, and many standard medicines are derived from herbs. Most herbal remedies have fewer adverse effects than standard medicines, but they all need to be used with care.
You should be cautious about taking St John’s wort if you have a diagnosis of bipolar disorder because, as with all antidepressants, it has been known to cause hypomania, or rapid switching from a low to a high mood (see Hypomania and mania.)
You should be cautious about taking St John's wort if you are pregnant or breastfeeding, because there is no information on its safety in these situations.
There is also no information about its safety for children under the age of 18.
What are the side effects?
The most commonly reported side effects of St John's wort include:
- symptoms affecting your stomach and digestion such as feeling sick, being sick, diarrhoea
- allergic reactions
- feeling tired
Some people get a dry mouth.
A rare side effect is increased sensitivity to sunlight; if you think this is affecting you, you should consider using a high factor sunscreen, or cover up, or stay out of the sun. You should also be cautious with taking St John’s wort if you use a lamp box for seasonal affective disorder. (See Seasonal affective disorder.)
Can I take St John’s wort with other medicines?
St John's wort has significant interactions with a large number of medicines which are in common use (in addition to those mentioned below). This means that it may affect the levels of some other drugs in the body, and may make them less effective, or more likely to cause adverse effects. These drugs include both prescribed drugs and medicines you can buy for yourself, such as paracetamol.
Because of this, it is very important that you get professional advice from a pharmacist, medical herbalist or doctor before taking St John's wort at the same time as any other medicine.
- You should not take St John's wort at the same time as any other antidepressant.
- St John's wort may prolong the effects of some sleeping pills and anaesthetics. If you are to receive an anaesthetic you should tell the anaesthetist if you are taking St John's wort.
- St John's wort reduces the level of oral contraceptives in your blood, increasing the risk of pregnancy and breakthrough bleeding.
Will I get withdrawal symptoms when I stop taking St John’s wort?
Information on withdrawal symptoms is anecdotal and inconsistent. Some people have reported feeling sick, dizzy and tense when they stopped taking St John’s wort abruptly.
As St John’s wort has similar properties to prescribed antidepressants, it is advisable to withdraw slowly to reduce the chance of withdrawal symptoms, especially if you have been taking it for longer than a few weeks.
Prescription and licensing
Can I get St John’s wort on prescription?
St John’s wort is available on prescription in many European countries, and is a prescription-only drug in Ireland; however, doctors in England and Wales do not normally write prescriptions for it.
This is because its use is not recommended by the British National Formulary (the main drug reference book used by health professionals) or by the National Institute for Health and Clinical Excellence (NICE). It is also not supported by NHS funding in many areas.
You can buy it over the counter, and if your doctor were to suggest you try it, you would usually have to buy it for yourself. It is readily available in many health-food shops and pharmacies.
Is St John’s wort licensed by the MHRA?
The MHRA (Medicines and Healthcare products Regulatory Agency, responsible for licensing medicines in the UK) licenses St John’s wort products under the Traditional Herbal Medicine scheme. Under this scheme, registration is based on the long-standing use of a plant as a traditional herbal medicine, and is not based on clinical trials.
Not all St John’s wort products are licensed in this way yet; those that are may be marked with the registration mark shown here, though this is not compulsory.
This indicates that the herbal medicine is acceptably safe when it is used according to the instructions on the packaging. The product should also have a registration number, starting with the letters THR.
British Herbal Medicine Association
tel: 0845 680 1134
Offers publications about herbal medicines
Medicines and Healthcare products Regulatory Agency (MHRA)
For more information about herbal medicines registration, and registered products.
National Institute of Medical Herbalists
tel: 01392 426022
A list of NIMH members is available on this site.
To be revised 2014
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