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Interactions between herbal remedies and other medicines

Updated on January 31, 2014

According to a review on the use of herbal remedies by patients with cardiovascular diseases, published in February 2010 in the Journal of the American College of Cardiology by physicians from the Mayo Clinic (reference below), consultations with practitioners of complementary and alternative therapies account for $30 billion spending per year in the USA and more visits are paid to these practitioners than to primary care physicians. Herbal remedies are one of the most popular forms of alternative medicine.

Moreover, very many herbal remedies are freely available for purchase and thus are widely consumed as self-medication without prior consultation. The Mayo paper claims that herbal remedies and high-dose vitamin supplements are used by more than 15 million people in the USA, with herbal remedies forming the bulk of this use.

At present, herbal remedies do not have to go through the years of testing required by the FDA (US Food and Drug Administration) for pharmaceuticals. On the other hand, the regulations require them to be marketed as dietary supplements and no claims concerning curative properties or other health benefits can be made on the packaging or in advertising. Partly for this reason, many not only see herbal remedies as being “gentler” than synthetic medicines, but also do not feel it necessary to tell their physician that they are using herbal remedies.

Herbal remedies can have as potent pharmacological effects as any conventional medicine. They can interact with medicines to produce unexpected, and even dangerous, effects.

This article summarises some of the interactions that can occur between six popular herbal remedies (St John’s Wort, Ginkgo biloba, ginseng, echinacea, valerian, evening primrose) and other medicines.

Interactions between St John's Wort and many medicines are potentially dangerous
Interactions between St John's Wort and many medicines are potentially dangerous

St John's Wort

St John’s wort is widely used for depression, sleep disorders and anxiety and indeed has been shown in some studies to be as effective as some antidepressants.

However, St John’s wort can interact with a very large number of medicines.

Interactions that make other medicines less effective

In many cases, this herb competes with other medicines and lowers their concentration in the blood, thus making them less effective. Examples of such interactions include:

  • antihistamines (Allegra, Zyrtec, Claritin)
  • immunosuppressants such as cyclosporine, methotrexate, tacrolimus and azothiprine. These drugs are used in autoimmune diseases such as lupus, and when taken together with St John’s wort may not be effective enough to control the symptoms. Immunosuppressants are also given to transplant recipients. The effect of St John’s wort could lower the levels of the immunosuppressant to such a degree that it can no longer prevent the transplanted organ being rejected.
  • cardiovascular drugs such as digoxin (Lanoxin), reserpine and some calcium channel blockers (both used to lower high blood pressure), statins (cholesterol-lowering drugs), warfarin (blood-thinner)
  • contraceptive pills are potentially made less effective, since there have been reports of women having breakthrough bleeding when taking St John’s wort at the same time
  • drugs against HIV and AID: protease inhibitors and non-nucleoside reverse transcriptase inhibitors
  • theophylline (used to help breathing in chronic bronchitis, emphysema and severe asthma)

Interactions that increase side effects of other medicines

In other cases, St John’s wort increases the activity of medicines or mimics some of their activity, thus increasing the frequency and severity of side effects. These medicines include:

Serotonin syndrome is due to an excess of serotonin in the body. In severe cases, symptoms include high blood pressure, fever, convulsions and confusion. The condition can progress to coma and death. Immediate medical help is needed if serotonin syndrome is suspected.

  • Antidepressants: SSRIs (e.g. Celexa, Prozac, Zoloft, Paxil), tricyclic antidepressants (e.g. amitryptyline, imipramine) and MAO inhibitors. Not only are side effects increased, but there is a danger of serotonin syndrome developing.
  • Dextromethorphan is found in many over-the-counter cough and cold medicines. As well as an increase in side effects, there is a danger of serotonin syndrome.
  • Migraine medication (triptans): As well as an increase in side effects, there is a danger of serotonin syndrome.
  • Sleeping pills, anticonvulsants (e.g. valproic acid, phenytoin), barbiturates and benzodiazepines (Valium, Xanax) all have their sedative effect increased by St John’s wort. This can lead to potentially fatal respiratory depression.


Ginkgo biloba increases the risk of bleeding
Ginkgo biloba increases the risk of bleeding

Ginkgo biloba

Ginkgo is particularly popular as an herbal remedy to prevent or treat dementia, memory loss and other cognitive decline. The benefit of ginkgo biloba supplements has been demonstrated in a number of conditions and diseases.

  • Ginkgo decreases the “stickiness” of blood platelets and thus increases the risk of bleeding. It is therefore potentially dangerous to take ginkgo together with medicines that increase the risk of bleeding, such as aspirin, "blood thinners" (anticoagulants) e.g. heparin and warfarin, non-steroidal anti-inflammatory drugs (ibuprofen, naproxen) anti-platelet drugs e.g. clopidogrel (Plavix).
  • Because ginkgo is thought to influence blood levels of sugar and insulin, it may potentially be dangerous when taken with antidiabetic drugs and insulin.
  • Ginkgo taken in high doses may possibly make some anticonvulsants, such as carbamazepine and valproic acid, less effective.
  • Theoretically, ginkgo could increase the side effects of MAO inhibitors and SSRIs and possibly increase the risk of serotonin syndrome. However, this suspicion is based on animal studies and there have been no reports of such incidents in humans.

Ginseng can interfere with the treatment of diabetes
Ginseng can interfere with the treatment of diabetes

Ginseng

Ginseng is used as a general tonic, aphrodisiac, and also to boost the immune system and resistance.

Siberian ginseng (Acanthopanax senticosus,  Eleutherococcus senticosus) can increase the side effects of digoxin and some sedatives, especially barbiturates.

American ginseng (Panax quinquefolium) and Asian ginseng (Panax ginseng) can:

  • lower blood sugar levels and therefore be potentially be dangerous when taken with antidiabetic drugs and insulin
  • further increase the risk of bleeding when taken with medicines that increase the risk of bleeding, such as aspirin, heparin, non-steroidal anti-inflammatory drugs (ibuprofen, naproxen) anti-platelet drugs e.g. clopidogrel (Plavix). Paradoxically, though, it decreases the anticoagulant efficacy of warfarin by lowering levels of warfarin in the blood.
  • increase the side effects of MAO inhibitors
  • alter the effects of medicines taken for heart disease or high blood pressure
  • possibly block the pain-relieving activity of morphine

Evening Primrose

Evening primrose oil is widely used to treat skin problems and for female problems such as premenstrual tension, menopausal symptoms and breast tenderness during the menstrual cycle.

It is thought to decrease the seizure threshold, and therefore will increase the risk of seizures associated with phenothiazine drugs (e.g. chlorpromazine, perphenazine, thioridazine), which are used to treat schizophrenia.

Because of its effect on the seizure threshold, evening primrose oil may cause an established dose of an anti-epileptic drug to be less effective in preventing seizures.

Echinacea

Echinacea stimulates the immune system. It will therefore block the activity of immunosuppressants such as cyclosporine, methotrexate, tacrolimus and azothiprine used in autoimmune diseases and after organ transplantation.

Valerian

Valerian is used to help sleep and for its calming effect.

As a sedative itself, valerian will increase the sedative effects of sleeping pills, anticonvulsants (e.g. valproic acid, phenytoin), barbiturates and benzodiazepines (Valium, Xanax). This can lead to potentially fatal respiratory depression. Likewise, it may increase the effects of general anaesthesia if used shortly before surgery.

Stay aware!

These are just some of the interactions that can occur between popular herbal remedies and other medicines. If you intend to take a herbal remedy and you are on other medication, you should always ask your doctor or pharmacist for advice before starting. Likewise, if you regularly use a herbal remedy, you should tell your doctor this when you receive a prescription for a new medicine.

This article was based primarily on information from the following resources:
Complementary and Alternative Medicine Index, University of Maryland Medical Centre
Medline Plus

Reference
Ara Tachjian, Viqar Maria, and Arshad Jahangir
Use of Herbal Products and Potential Interactions in Patients With Cardiovascular Diseases
J Am Coll Cardiol, 2010; 55:515-525

Photos:
St John’s Wort by Igor Savin (Игоревич); Ginseng by Richardfabi; Echinacea by RI on Wiki Commons
Ginkgo biloba plant by Marcefabi at http://www.arteyfotografia.com.ar/3111/fotos/

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    • WriteAngled profile image
      Author

      WriteAngled 4 years ago from Abertawe, Cymru

      Thank you, Carol! :)

    • carol7777 profile image

      carol stanley 4 years ago from Arizona

      I enjoyed this hub a lot and wanted to read some of your hubs after answering a question on forum. Thanks for a great and well researched hub.

    • WriteAngled profile image
      Author

      WriteAngled 5 years ago from Abertawe, Cymru

      I am not a medical practitioner and therefore cannot give specific advice on individual situations. What is written here are my findings from reputable sources. If you have any specific concerns, please talk to your own doctor and/or herbalist.

    • JoeLaBarbera profile image

      JoeLaBarbera 5 years ago from CT, USA

      Nice well written and useful hub.

    • camdjohnston12 profile image

      camdjohnston12 6 years ago

      Great hub! I really learned in this hub! Very informative plus well written. THanks.

    • WriteAngled profile image
      Author

      WriteAngled 6 years ago from Abertawe, Cymru

      Yes, of course. I would view that as a compliment. :)

    • RTalloni profile image

      RTalloni 6 years ago from the short journey

      Thanks for a detailed overview that can be used as an important resource. I would like to link it to my hub on St. John's Wort, if you have no objection.

    • WriteAngled profile image
      Author

      WriteAngled 7 years ago from Abertawe, Cymru

      Apologies for not having responded before, but I had to take an extended break from hubbing. Anne, I really cannot comment, because I am not a medical practitioner and therefore cannot give specific advice on individual situations. What is written here are my findings from reputable sources. I do think though that your husband should discuss this with this doctor.

    • mythbuster profile image

      mythbuster 7 years ago from Utopia, Oz, You Decide

      This is a much needed article, WriteAngled. I found the information very easy to understand. I've used Valerian and several other herbs mentioned in this article and had to discontinue use of Valerian and St. John's Wort. These substances were as strong as medical drugs and had the same effects as a medical drug providing me with too many negative/unwanted side-effects.

    • tonymac04 profile image

      Tony McGregor 7 years ago from South Africa

      I really found this Hub useful. I am all for alternative and herbal therapies but I aalso fully understand the problems that can arise through unexpected interactions with other drugs. I think people frequently believe that herbal therapies are drug free, which is not in fact the case. St John's Wort is in fact a drug, though of herbal origin. It is very important that people using these medications understand them and their effects, just as it is important for doctors when prescribing "conventional" allopathic medications explain them and their interactions properly with their patients.

      I think the main thing is to be aware, as you say, of both the herbal and "conventional" medications, whether taken separately or in combinations.

      Thanks for a well-researched and well-written Hub.

      Love and peace

      Tony

    • WriteAngled profile image
      Author

      WriteAngled 7 years ago from Abertawe, Cymru

      I'm glad it was a question of not agreeing, rather than something more serious, Ethel!

    • ethel smith profile image

      Eileen Kersey 7 years ago from Kingston-Upon-Hull

      You are so right. It is important to bear this in mind. I have tried St Johns Wort in the past and reading this hub now see why it did not agree with me.

    • Pamela99 profile image

      Pamela Oglesby 7 years ago from United States

      This is an excellent hub because the interactions between some herbal remedies and prescription drugs are often unknown.

    • emohealer profile image

      Sioux Ramos 7 years ago from South Carolina

      WriteAngled, a much needed article with much needed information. I often hesitate to share herbal tips and advice even with my vast knowledge because of these possibilities. The hub I wrote was the little bit of information I felt comfortable sharing on a broad scale. I feel much better with this advice interactions and will definitely take the time to learn more in this area....great tips, great hub!!!

    • Jen's Solitude profile image

      Jen's Solitude 7 years ago from Delaware

      WriteAngled, what a useful and very informative hub! I have wondered what medical conditions and medications conflict with herbal remedies and you have provided very good examples and links for further research. Thanks very much, I have bookmarked this hub.