Herbfacts

Herb-Drug Interactions

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.

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.