Herb-Drug Interactions - Vitamin Expert

Some licensed medicines, including herbal medicines, may affect the way other medicines work. This may include both over-the-counter (OTC) medicines that you can buy in a pharmacy or supermarket, or prescribed medicines. Occasionally, some foods can also affect the way particular medicines work. This is called an interaction and can make a particular medicine work more or less effectively.

Details of all herb-drug interactions can be seen on the approved Product Information Leaflet (PIL) for all medicines. The Medicines and Healthcare products Regulatory Agency (MHRA) have a list of approved Summary of Product Characteristics (SPC) for every licensed medicine which are available to view on the MHRA website. The SPC provides details of a medicine’s properties and the conditions for using it.

There are no known interactions between traditional herbal medicines, which means that you can safely take herbal medicines together.

A B C D E F G H I L M N O P R S V W

Herb	Botanical name	Herb-drug interactions Summary of Product Characteristics Section 4.5

Agnus castus berries	Vitex agnus castus L.	There are no published data available on drug interactions with extract of Agnus castus. Animal experiments have shown that the drug has a dopaminergic effect and so, theoretically, there could be a reduction in the effectiveness of dopamine-receptor agonists, and/or a potentiation of dopamine-receptor antagonists.
Arnica	Arnica montana L.	None known.
Artichoke leaf	Cynara scolymus L.	There are no published data available on drug interactions with extracts of artichoke leaf.
Asparagus root	Asparagus officinalis L.	No interaction studies have been performed.
Bayberry bark	Myrica cerifera L.	No studies have been carried out to determine if drug interactions occur with this herb.
Black Cohosh	Cimicifuga racemosa L. Nutt	No studies have been conducted to determine if drug interactions occur with this herb.
Bladderwrack	Fucus vesiculosus L.	Theoretical interaction with anticoagulants.
Boneset	Eupatorium perfoliatum L.	None known.
Burdock root	Arctium lappa L.	None known.
Butcher’s broom root	Ruscus aculeatus L.	None known.
Cape aloe	Aloe ferox Mill	Hypokalaemia (resulting from long-term laxative abuse) potentiates the action of cardiac glycosides and interacts with antiarrhythmic medicinal products which induce reversion to sinus rhythm (e.g. quinidine) and with medicinal products including QT-prolongation. Concomitant use with other medicinal products inducing hypokalaemia (e.g. diuretics, adrenocorticosteroids and liquorice root) may enhance electrolyte imbalance.
Cascara bark	Rhamnus purshianus D.C.	Hypokalaemia (resulting from long-term laxative abuse) potentiates the action of cardiac glycosides and interacts with antiarrhythmic medicial products which induce reversion to sinus rhythm (e.g. quinidine) and with medicinal products including QT-prolongation. Concomitant use with other medicinal products inducing hypokalaemia (e.g. diuretics, adrenocorticosteroids and liquorice root) may enhance electrolyte imbalance.
Celery seeds	Apium graveolens L.	None known. However there is a theoretical risk that Celery seed may interact with anti-coagulant medicines and therefore should not be used in patients receiving anti-coagulant medicines.
Centaury herb	Centaurium erythraea Rafn.	No interaction studies have been performed.
Dandelion root	Taraxacum officinale Weber	Hypokalaemia (resulting from long-term laxative abuse) potentiates the action of cardiac glycosides and interacts with antiarrhythmic medical products which induce reversion to sinus rhythm (e.g. quinidine) and with medicinal products including QT-prolongation. Concomitant use with other medicinal products inducing hypokalaemia (e.g. diuretics, adrenocorticosteroids and liquorice root) may enhance electrolyte imbalance.
Devil’s Claw	Harpagophytum procumbens D.C.	No studies have been carried out to determine if drug interactions occur with this herb.
Echinacea aerial parts	Echinacea purpurea (L.) Moench	Not to be used concomitantly with immunosuppressant medications such as ciclosporin and methotrexate.
Echinacea root	E.purpurea (L.) Moench, E. pallida Nutt., E. angustifolia (D.C.)	Not to be used concomitantly with immunosuppressant medications such as ciclosporin and methotrexate.
Elecampane root	Inula helenium L.	No studies have been carried out to determine if drug interactions occur with this herb.
Elder flower	Sambucus nigra L.	No studies have been carried out to determine if drug interactions occur with this herb.
Fennel fruit	Foeniculum vulgare var Dulce Miller	Hypokalaemia (resulting from long-term laxative abuse) potentiates the action of cardiac glycosides and interacts with antiarrhythmic medicinal products which induce reversion to sinus rhythm (e.g. quinidine) and with medicinal products including QT-prolongation. Concomitant use with other medicinal products inducing hypokalaemia (e.g. diuretics, adrenocorticosteroids and liquorice root) may enhance electrolyte imbalance.
Feverfew	Tanacetum parthenium L. Schultz Bip	Drugs that affect coagulation and bleeding: Feverfew theoretically may increase the risk of bleeding when taken with drugs that affect coagulation and bleeding. Some examples include aspirin, anticoagulants such as warfarin or heparin, anti-platelet drugs such as clopidogrel, and non-steroidal anti-inflammatory drugs such as aspirin, ibuprofen and naproxen.
Frangula bark	Rhamnus frangula L.	Enteral absorption of concomitantly administered medicines may be delayed by bulk forming laxatives such as Linoforce granules. For this reason Linoforce granules should not be taken ½ to 1 hour before or after intake of other medicinal products. In order to decrease the risk of gastrointestinal obstruction (ileus), this product should only be used together with medicinal products known to inhibit peristaltic movement (e.g. opiods, loperamide) under medical supervision. Hypokalaemia (resulting from long-term laxative abuse) potentiates the action of cardiac glycosides and interacts with antiarrhythmic medicinal products, with medicinal products which induce reversion to sinus rhythm (e.g. quinidine) and with medicinal products inducing QT-prolongation. Concomitant use with other medicinal products inducing hypokalaemia (e.g. diuretics, adrenocorticosteroids and liquorice root) may in case of abuse enhance electrolyte imbalance.
Fumitory	Fumaria officinalis L.	None known.
Gentian root	Gentiana lutea L.	None known.
Ginger rhizome	Zingiber officinale ROSCOE	Anticoagulants (warfarin, phenprocoumon, heparin), anti-platelet drugs (clopidogrel), non-steroidal anti-inflammatory medicines (eg. aspirin, ibuprofen, naproxen).
Ginkgo	Ginkgo biloba L.	Specific studies have not been conducted to determine whether drug interactions occur. Due to a potential interaction with CYP2C19 a medical practitioner should be consulted prior to the concomitant use of drugs which are known substrates, such as proton pump inhibitors. There have been isolated case reports of decreased serum concentrations of both valproic acid and phenytoin resulting in seizures. Caution is advised in such cases and a medical practitioner should be consulted. Concomitant administration of ginkgo and anti-coagulants such as coumarins (warfarin or heparin) or non-steroidal anti-inflammatory drugs (including ibuprofen and acetylsalicylic acid) should be avoided due to potential effects on bleeding time prolongation. There have been isolated case reports but this has not been substantiated in pharmacological trials. There is limited evidence of in-vitro effects of ginkgo on CYP1A2, CYP2C9, CYP2D6 and CYP1E2 but clinical studies have found no clinically relevant effects.
Hemlock Spruce	Pinus canadensis L.	No studies have been carried out to determine if drug interactions occur with this herb.
Hops	Humulus lupulus L.	None known.
Horse chestnut seeds	Aesculus hippocastanum L.	None known.
Horsetail	Equisetum arvense L.	None known.
Hyssop	Hyssopus officinalis L.	None known.
Ivy leaf	Hedera helix L.	None known.
Lemon balm leaf	Melissa officinalis L.	Concomitant use with synthetic sedatives (benzodiazepines) is not recommended.
Linseed	Linum usitatissimum L.	Enteral absorption of concomitantly administered medicines may be delayed by bulk forming laxatives such as Linoforce granules. For this reason Linoforce granules should not be taken 30-60 minutes before or after intake of other medicinal products. In order to to avoid gastrointestinal obstruction (ileus), this product should only be used with medicinal products known to inhibit peristaltic movement (e.g.: opioids, loperamide) under medical supervision. Hypokalaemia (resulting from long-term laxative abuse) potentiates the action of cardiac glycosides and interacts with antiarrhythmic medicinal products, with medicinal products which induce reversion to sinus rhythm (e.g. quinidine) and with medicinal products inducing QT-prolongation. Concomitant use with other medicinal products inducing hypokalaemia (e.g. diuretics, adrenocorticosteroids and liquorice root) may in case of abuse enhance electrolyte imbalance.
Lobelia	Lobelia inflata L.	No studies have been carried out to determine if drug interactions occur with this herb.
Lovage root	Levisticum officinale Koch.	No interaction studies have been performed.
Milk thistle fruit	Silybum marianum L. Gaertner	In vitro, Milk Thistle extract resulted in inhibition of CYP isoenzymes. However, the clinical relevance of these findings is not established.
Nettle leaf	Urtica dioica	None known.
Nettle root	Urtica dioica L.	None known.
Oat herb	Avena sativa L.	None known.
Parsley herb	Petroselinum crispum(Mill.) A.W.Hill	No interaction studies have been performed.
Passion flower	Passiflora incarnata L	Although no clinical data about interactions with synthetic sedatives are available, concomitant use with synthetic sedatives (benzodiazepines) is not recommended.
Pelargonium root	Pelargonium sidoides DC	Drug interactions have not been reported to date. However, due to the potential influence of Pelargonium on coagulation parameters, the possibility that this product enhances the effect of coagulation-inhibiting drugs such as warfarin in cases of simultaneous intake cannot be excluded.
Peppermint oil	Mentha piperita L.	None known.
Pine spruce shoots	Picea abies L. Karsten	No interaction studies have been performed.
Pleurisy root	Asclepias tuberosa L.	No studies have been carried out to determine if drug interactions occur with this herb.
Primula flowers	Primula veris L.	Appropriate studies have not been conducted to determine if drug interactions occur. The potential of pharmacodynamic and pharmacokinetic drug interactions cannot be exluded.
Pumpkin seeds	Cucurbita pepo L.	No interaction studies have been performed.
Red Peony	Paeonia lactiflora Pallas	No studies have been carried out to determine if drug interactions occur with this herb.
Rhodiola root	Rhodiola rosea L.	In vitro, Rhodiola rosea extract at a concentration of 10 microgram/ml resulted in inhibition of CYP2C9 and CYP2C19 isoenzymes. The clinical relevance of these findings is not known.
Rosemary leaf	Rosmarinus officinalis L.	No interaction studies have been performed.
Sage leaves	Salvia officinalis L.	No interactions have been reported. An intake of Sage leaf preparations might influence the effect of medicinal products acting via GABA receptors (barbiturates, benzodiazepines) even if not seen clinically. Therefore the concomitant use with such medical products is not recommended.
Saw Palmetto	Serenoa repens(Bartram) Small	Limited interaction studies have identified no clinically important drug interactions. It does not appear to significantly affect the cytochrome P450 linked enzyme system.
Senna leaf Tinnevelly	Cassia angustifolia Vahl	Hypokalaemia (resulting from long-term laxative abuse) potentiates the action of cardiac glycosides and interacts with antiarrhythmic medicinal products which induce reversion to sinus rhythm (e.g. quinidine) and with medicinal products including QT-prolongation. Concomitant use with other medicinal products inducing hypokalaemia (e.g. diuretics, adrenocorticosteroids and liquorice root) may enhance electrolyte imbalance.
Senna leaf	Cassia senna L.	Hypokalaemia (resulting from long-term laxative abuse) potentiates the action of cardiac glycosides and interacts with antiarrhythmic medicinal products which induce reversion to sinus rhythm (e.g. quinidine) and with medicinal products including QT-prolongation. Concomitant use with other medicinal products inducing hypokalaemia (e.g. diuretics, adrenocorticosteroids and liquorice root) may enhance electrolyte imbalance.
Skunk cabbage root	Symplocarpus foetidus L.	No studies have been carried out to determine if drug interactions occur with this herb.
Sorrel	Rumex acetosa L.	Appropriate studies have not been conducted to determine if drug interactions occur.The potential of pharmacodynamic and pharmacokinetic drug interactions cannot be exluded.
Squill	Urginea maritima L.	No studies have been carried out to determine if drug interactions occur with this herb. In view of the potential for Squill to interact with other medicines administered concurrently, Squill should not be taken with digoxin or any medicine for heart conditions.
St John’s wort	Hypericum perforatum L.	Anaesthetics, analgesics, antianginals, anti-arrhythmics, antibacterials, anticoagulants, antidepressants, antiepileptics, antifungals, antimalarials, anti-parkinson drugs, anti-psychotics, antivirals (HIV), anxiolytics, barbiturates, calcium channel blockers, cardiac glycosides, CNS stimulants, cytotoxics, hormonal contraceptives, HRT, hormone antagonists, diuretics, 5HT agonists, immunosupressants, lipid regulating drugs, lithium, proton pump inhibitors, theophylline, thyroid hormones (thyroxine), oral hypoglycaemic drugs.
Valerian root	Valeriana officinalis L.	Only limited data on pharmacological interactions with other medicinal products are available. Additive effects with hypnotics and other sedative drugs cannot be excluded and therefore co-medication is not recommended as a general precaution. The effect of Valerian may be potentiated by alcohol. Excessive concomitant consumption of alcohol should therefore be avoided.
Vervain	Verbena officinalis L.	Appropriate studies have not been conducted to determine if drug interactions occur.The potential of pharmacodynamic and pharmacokinetic drug interactions cannot be exluded.
White cedar	Thuja occidentalis L.	None known.
White horehound leaves	Marrubium vulgare L.	No studies have been carried out to determine if drug interactions occur with this herb.
Wild Indigo	Baptisia tinctoria R.Br.	None known.
Wild lettuce	Lactuca virosa L.	None known.