Possible Side Effects of St. John’s Wort

  St John’s wort is a plant with a bare trunk and yellow flowers, which grows mainly in Europe, Asia and North America. All growing parts of the plant above the soil are used to manufacture this herbal remedy. This initially results in a crude form of the herb called hypericum extract. There are often many differences in the ingredients and this can be due to variations in the species, ecological factors and when the plant is harvested.

 A number of active ingredients are known to be present in the hypericum extract, the most important ones being hypericin, hyperforin, flavanols and xanthones. Hypericum extract is thought to work in a similar way to antidepressant medicines, by affecting levels of neurotransmitters such as serotonin in the brain (however, the exact mechanism of action is not known).

 Recent work, published in the British Medical Journal, has suggested that St John’s wort is as effective as imipramine in controlling symptoms of mild to moderate depression. Other research has also shown that this herb may be as effective as selective serotonin reuptake inhibitors (SSRIs) in treating mild to moderate depression.

 However, recent studies also suggest that St John’s wort is of no benefit in treating major depression of moderate severity. More research is required to help us know whether St. John’s wort has value in treating other forms of depression.

St John’s wort is sometimes used for other nervous complaints such as bedwetting and stuttering. When applied topically to the skin as an oily solution, it is thought to be useful for helping with arthritic pains, burns, sunburn and ulcers.

What is it used for? 

• Mild to moderate (not severe) depression.
• Anxiety and agitation.
• Impaired concentration.
• Dysthymia (variability in mood).
• Nerve pain (neuralgia).
• Sleep disturbances.

 Warning!

St John’s wort is an unlicensed herbal remedy. It has not been through the rigorous testing and quality procedures undertaken by the UK regulatory authority, the Medicines and Healthcare products Regulatory Agency. To become an approved licensed product, St John’s wort would need to undergo strict clinical trial testing. This would then officially establish its effectiveness and ensure it is totally safe for people to take. However, based on current research, St John’s wort exhibits relatively few side effects compared to other antidepressant medicines.

It is advisable to stick to the same brand of St John’s wort. The amount of active ingredients can vary from one product to another, resulting in varied levels of benefit if different products are used. Switching products could also result in a varying effect on medicines that interact with St John’s wort.

St John’s wort liquid extracts and tinctures contain alcohol and may cause drowsiness. If affected, do not drive or operate machinery. Avoid alcoholic drinks.

If you are taking other medicines at the same time as this herbal remedy, do not stop taking St John’s wort suddenly. Seek the advice of your doctor or pharmacist first. This is because St John’s wort can affect other medicines see below.  

 Use with caution in

Sunbathing and while using sunbeds. St John’s wort may make your skin more sensitive to the sun/sunlamp and cause it to burn. To avoid this it is advisable to use a sunscreen product to protect the skin.

 Not to be used in

People with light-sensitive skin conditions (photodermatitis).

St John’s wort should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy. If you feel you have experienced an allergic reaction, stop using St John’s wort and inform your doctor or pharmacist immediately.

 Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or trying to conceive before using any medicine.

 St John’s wort should not be used by pregnant or breastfeeding women due to lack of information of its safety during pregnancy or breastfeeding.

 

Side effects

Medicines and their possible side effects can affect individual people in different ways. Listed below are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience this or any side effect.

Common side effects 

• Dry mouth.
• Nausea.
• Headache.
• Constipation.
• Dizziness.
• Confusion.
• Tiredness.
• Hypersensitivity of the skin to sunlight (photosensitivity).
• Rare side effects
• Blood clotting disorders.
• Psychiatric disorders.
• Liver disorders.

 The side effects listed above may not include all of the side effects reported by the manufacturers.

 For more information about any other possible risks associated with this medicine, please read the information provided with the herbal remedy or consult your doctor or pharmacist.

 How can St John’s wort affect other medicines?

St John’s wort has the potential to interact with a number of medicines, stopping them from working properly. For this reason it is important to check with your doctor or pharmacist before you take St John’s wort, so they can determine if it is safe to take with your existing medicines.

St John’s wort should not be taken with any of the following medicines, because it may decrease the amount of these medicines in the blood, thus making them less effective:  

• anticonvulsants (eg carbamazepine, phenobarbital, phenytoin)
• aprepitant
• ciclosporin
• digoxin
• eplerenone
• imatinib
• irinotecan
• ivabradine
• maraviroc
• non-nucleoside reverse transcriptase inhibitors for HIV infection (eg efavirenz, nevirapine)
• oestrogens and progestogens, eg in oral contraceptive pills (see below)
• protease inhibitors for HIV infection (eg amprenavir, atazanavir, darunavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, tipranavir)
• tacrolimus
• telithromycin
• theophylline
• voriconazole

• warfarin.

 If you are taking any of these medicines you should not start taking St John’s wort.

If you are already taking St John‘s wort with any of these medicines you will need to stop taking the St John’s wort. However, you should consult your doctor before doing this, because stopping the St John’s wort could cause the amount of these medicines in the blood to increase, with a risk of side effects. Your doctor may need to check the blood level of your medicine and alter your dose to prevent this.

You should not take St John’s wort if you are taking an oral contraceptive pill, because it may stop your pill from working, risking unwanted pregnancy and breakthrough bleeding. If you are already taking St John’s wort with an oral contraceptive it is safe for you to stop taking it without consulting your doctor, but you should mention it when you next consult your doctor.

 St John’s wort should also not be taken with any of the following medicines because it may increase the risk of their side effects:

 triptans for migraine (eg sumatriptan, naratriptan, rizatriptan, zolmitriptan)

SSRI antidepressants (eg citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline).

 You should always seek advice from your doctor or pharmacist before adding St John’s wort to the medicines you are already taking. If you are already taking St John’s wort, you should always seek advice from your doctor or pharmacist before starting any new medicines, or stopping any existing ones.

The information provided on this site is for informational  purposes only and is not a substitute for medical advice or treatment  for any medical conditions. Consult with a healthcare professional before  starting any diet, exercise or supplementation program, before taking  any medication, or if you have or suspect you might have a health problem.  

References

Nahrstedt A. & Butterweck V. Pharmacopsychiat. 1997; 30 Suppl 2: 129-134.

Linde K et al. British Medical Journal 1996; 313: 253-258.

Linde K. & Malrow D. The Cochrane Library 2000.

Woelk H. British Medical Journal 2000; 321: 536-539.

Fugh-Berman A. Lancet 2000; 355: 134-138.

Schrader E. Int Clin Psychopharmacol 2000;15:61-8.

Breckenridge A. Committee on Safety of Medicines 29 February 2000.

Linde K, Mulrow CD, Berner M, Egger M. St John’s Wort for depression. Cochrane Database of Systematic Reviews 2005, Issue 2.

 

 References

Nahrstedt A. & Butterweck V. Pharmacopsychiat. 1997; 30 Suppl 2: 129-134.

Linde K et al. British Medical Journal 1996; 313: 253-258.

Linde K. & Malrow D. The Cochrane Library 2000.

Woelk H. British Medical Journal 2000; 321: 536-539.

Fugh-Berman A. Lancet 2000; 355: 134-138.

Schrader E. Int Clin Psychopharmacol 2000;15:61-8.

Breckenridge A. Committee on Safety of Medicines 29 February 2000.

Linde K, Mulrow CD, Berner M, Egger M. St John’s Wort for depression. Cochrane Database of Systematic Reviews 2005, Issue 2.

http://www.netdoctor.co.uk/diseases/depression/stjohnswort_000316.htm

Acessed 10-12-2009