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  • Q&A with Australian Health Practitioners

    St John's Wort and high blood pressure

    It has been suggested that I take St John's Wort, however I am very cautious about taking anything that may have any contraindications. I have read that St John's Wort can cause problems if you have high blood pressure. I woud be interested in hearing from anyone who has taken this and what their experience was.

    Thank you - Alex
  • Find a professional to answer your question

  • 33


    beyondblue is a national, independent, not-for-profit organisation working to address issues associated with depression, anxiety and related disorders in Australia.beyondblue is a bipartisan initiative of … View Profile

    Hi Alex, yes it is true that St John's Wort interacts with many prescription medications, either affecting how they work, or in some instances producing serious side effects.  There are a number of mendications (eg Warfarin, Digoxin, oral contraceptives, SSRO antedepressants to name a few) that you should not take with St John's Wort.  Also, the research indicates St John's wort has only really shown to be effective for cases of mild depression at this stage.  If you would like some more information on the effectiveness of St John's Wort, how it works and the other medications that it should not be mixed with I would encourage you to have a look at the beyondblue Booklet:  A Guide to What Works for  Depression.  It is free and you can order it from the beyondblue website ( or call our information line 1300 22 4636 and we will send you a copy.    

  • 3


    Alex Smith

    HealthShare Member

    Thank you Dr Nicole, I will arrange to get a copy of the booklet.

    Kind regards - Alex

  • 5


    My research interests include immunology and the mechanisms of amyloid formation. The latter has implications for people who are dealing with Alzheimer's Disease, Parkinson's Disease … View Profile

    There is evidence that St John's Wort can interact in a negative way with many other medications.

    There is a list of those possible interactions here: .

    I suggest that you check out that list and, if there are medications there which you have been prescribed, talk about that with your clinical care team.

  • 18


    Arlene is a registered practising dietitian, with a private practice in the Eastern Suburbs of Sydney, and has built a strong business over the last … View Profile

    St. John's wort interacts with a large number of medications. In most cases, St. John's wort decreases the effectiveness of the medication; in other cases, however, St. John's wort may increase the effects of a medication. The interaction is variable so must be discussed with your doctor. For example:

    Using St. John's wort together with ethanol can increase nervous system side effects such as dizziness, drowsiness, and difficulty concentrating. Some people may also experience impairment in thinking and judgment. You should avoid or limit the use of alcohol while being treated with St. John's wort. Do not use more than the recommended dose of St. John's wort, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medication without first talking to your doctor.

    While you are taking St. John's wort, you must not eat or drink certain foods and beverages that are high in tyramine. Eating these foods while you are taking St. John's wort can raise your blood pressure to dangerous levels. This may cause life threatening symptoms such as sudden and severe headache, confusion, blurred vision, problems with speech or balance, nausea, vomiting, chest pain, seizure (convulsions), and sudden numbness or weakness (especially on one side of the body). Call your doctor at once if you have any of these symptoms. Foods that are high in tyramine include: air dried meats, aged or fermented meats, sausage or salami, pickled herring, and any spoiled or improperly stored beef, poultry, fish, or liver, red wine, beer from a tap, beer that has not been pasteurize, aged cheeses, including blue, brick, brie, cheddar, parmesan, romano, and swiss, sauerkraut, over the counter supplements or cough and cold medicines that contain tyramine, soy beans, soy sauce, tofu, miso soup, bean curd, fava beans, or yeast extracts (such as Marmite). Caffeine intake should be limited as well.

    St. John's wort may alter the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

    St. John's wort may alter blood sugar levels. Caution is advised when using medications that may also alter blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

    St. John's wort may affect blood pressure. Caution is advised in people taking drugs that affect blood pressure.

    Prior to taking St Johns Wort you must speak to your doctor about how it might interact with your other medication.





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