Herbs with Interactions

Men's Health, Women's Health | October 31, 2017 | Author: Naturopath

Alternative Therapies

Herbs with Interactions

While natural therapies are becoming increasing popular, many people are unaware that there are possible side-effects or interactions with medications. This often occurs in people who self-prescribe herbal supplements instead of going through a qualified naturopath or herbalist. It is also common for people to not disclose what supplements they are taking to their doctor. It is important that if you are taking any herbal medicines that you run it through your GP or naturopath to see if it is safe.

Here are some of the most commonly supplemented herbs which may have possible contraindications

St John’s Wort

St Johns WortA popular, natural alternative to prescribed antidepressants that is frequently recommended by both doctors and naturopaths to boost mood and reduce anxiety. It works in a similar way to selective serotonin reuptake inhibitors and has been clinically proven for mild to severe depression. Naturopaths with more knowledge about other traditional uses of the herb will also use it to treat viral illnesses and conditions that affect nerves such as neuralgia and shingles.

Adverse reactions

Approximately 1 in 30,000 people will experience side effects including those associated with drug interactions. The most common adverse reaction is photosensitivity (sensitivity to light). Although extremely rare, it can affect 1 in 300,000 treated cases if higher than recommended doses are taken.

Drug interactions

St John’s Wort is one of very few herbs that has been tested against numerous drugs to determine its interactions. The active constituent hypericin, is the main cause for concern as it decreases oral availability of certain drugs, while also increasing its clearance from the body—ultimately reducing its efficacy. In some cases, the dose of drugs if taken concurrently with St John’s wort may need to be adjusted. Speak to your doctor if you are taking alprazolam, amitriptyline, antidepressants, anticonvulsants, antineoplastic drugs, atorvastatin, bupropion, digoxin, oral contraceptives and cancer drugs. Although no adverse reactions have been identified in pregnant women, St John’s Wort is generally not recommended in pregnancy.


In Ayurvedic medicine, turmeric is traditionally used to improve digestion, relieve gas, dispel worms, dissolve gallstones, relieve arthritis and purify the blood. If you are taking curcumin or powdered turmeric for joint pain and inflammation— here’s some things you need to know.


Contraindications and cautions

Large doses in susceptible people may cause gastrointestinal irritation as well as nausea and diarrhoea. It is contraindicated in bile duct obstruction and high doses are probably best avoided in males and females wanting to conceive. Curcumin is contraindicated in breast cancer patients who are treated with cyclophosphamide until further studies have been done. Due to antiplatelet activity and a possible increased risk in bleeding it is recommended supplements are ceased 1 week prior to surgery. Caution is advised in people who take antiplatelet and anticoagulant drugs as it may have an additive effect and increase the risk of bleeding. Amounts taken in the diet are likely to be safe.


bilberriesBilberries have been used as a food for centuries and are valued for their nutritional value and taste. Due to their high antioxidant content they are useful in treating eye disorders such as poor night vision, retinopathy, glaucoma, myopia, dry eye and more. These antioxidants also benefit the heart and gastrointestinal system by providing anti-inflammatory actions.


Bilberry is considered a safe herb which is well tolerated. However, there are some minor areas of caution. Doses higher than 170mg should be used in caution in people with haemorrhagic disorders due to an increased risk in bleeding. Avoid use with the chemotherapy drug topoisomerase until its safety can be established. In diabetics taking hypoglycaemic medication, bilberry may theoretically increase its effectiveness. Due to bilberries high tannin content it may reduce iron absorption from supplements. It is recommended that they be consumed 2 hours apart. During pregnancy, bilberry is likely to be safe when consumed in dietary amounts.


A popular herb for all things cold and flu. Echinacea helps to support the immune system and fight off infection. It is usually a well-tolerated herb with only minor adverse reactions being reported.

EchinaceaSide effects include gastrointestinal symptoms and rashes. However, cases of allergic reactions have been reported resulting in itchy skin, hives, rash, swelling of the skin and anaphylaxis. This is especially the case in people with known plant allergies. In asthmatics, echinacea is considered a safe herb but should be taken with caution— in rare instances it has been known to exacerbate symptoms.

Safety profile

Echinacea appears to increase the immunostimulatory activity of low-dose cyclophosphamide. This may be an issue in autoimmune disease where low doses are used. Although there is no conclusive evidence to suggest an interaction, theoretically there may be an interaction with immunosuppressive agents. In clinical practice, echinacea has been successfully used in autoimmune disorders. Echinacea is considered suitable during pregnancy and offers a safe alternative for infections of all kind.


GinkgoAccording to clinical studies ginkgo is helpful for asthma, dementia, anxiety, vertigo, intermittent claudication and Raynaud’s syndrome. It works by increasing circulation, influencing brain chemicals, protecting nerve cells, stimulating nerve cells and reducing inflammation. The drug interactions of ginkgo are widely misunderstood. Here is what the evidence tells us.

Ginkgo and medications

Theoretically ginkgo has been contraindicated in people who are taking warfarin due to an increased risk of bleeding. However, more recent evidence from controlled clinical studies doesn’t support this conclusion and has failed to identify any interaction at all. This conclusion is supported by a systematic review.

Gingko enhances the activity of certain medications and reduces their side-effects. This includes antidepressants, cholinergics, cilostazol, cisplatin, clozapine and doxorubicin. In some cases, this may be beneficial if closely monitored by a health care professional. Overall ginkgo is a safe herb that is well tolerated with very rare instances of adverse reactions.

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Braun L, Cohen M. Herbs and natural supplements: An evidence based guide vol. 2. Edinburgh: Churchill Livingstone

Mills, S., & Bone, K. (2000). Principles and practice of phytotherapy: Modern herbal medicine. Edinburgh: Churchill Livingstone

Zhou S, et al. Pharmacokinetic interactions of drugs with St John's wort. J Psychopharmacol. 2004 Jun;18(2):262-76


Jawad M, et al. Safety and Efficacy Profile of Echinacea purpurea to Prevent Common Cold Episodes: A Randomized, Double-Blind, Placebo-Controlled Trial. Evid Based Complement Alternat Med. 2012;2012:841315


Jiang X, et al. Effect of ginkgo and ginger on the pharmacokinetics and pharmacodynamics of warfarin in healthy subjects. Br J Clin Pharmacol. 2005 Apr;59(4):425-32


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