This list provides common drug and nutrient interactions. Please note that the prescription drug listings are not all-inclusive; drugs listed are common examples.
Herb Drug Class Type of Interaction Alfalfa (Medicago sativa) – Leaf Anticoagulants2,4,9
e.g. Warfarin3 Interact
Reduced drug action due to Vitamin K content in alfalfa   Hormone replacement therapy2,4,9 Interact   Oral contraceptive2,4,9 Interact   Xenobiotics3 Increases rate of metabolism Remedies: Nutritional support, retained water, Cholesterol, menopause, addiction, urinary, bowel problems Aloe Vera – (A. vera) Latex Powder All drugs12 Aloe latex will bind all drugs   Antiarrhythmic agents5,11,12 
e.g. Quinidine Interact   Cardiac glycosides2,3,5,11,12
e.g. Digoxin5 Increases toxicity. Increases effect due to potassium loss, hypokalemia   Cortico-adrenal steroids5,11 Increases potassium deficiency   Diuretics3
e.g. Loop diuretics5
e.g. Thiazide diuretics5,11 Increases potassium loss
Interact
Interact   Laxative, stimulant20 Increases diarrhea, abdominal pain and fluid loss   Oral drugs3,11 Decreases absorption of drug due to reduction in bowel transit time   Glyburide4 Increases hypoglycemic effect Aloe Vera – Gel or Juice Glibenclamide3,4 Increases hypoglycemic effect Remedies: Immune system, Cancer, Heartburn, Arthritis Anise or Aniseed (Pimpinella anisum) – Seed Anticoagulants9 Excessive doses of Anise may interact with anticoagulants   Hormone Replacement Therapy9 Excessive doses of Anise may interact with HRT   Iron5 Enhances iron absorption across the intestinal mucosa   Oral contraceptive9 Excessive doses of Anise may interact   MAOIs9 Excessive doses of Anise may interact with MAOI therapy Remedies: Digestion, Infection, Respiratory problems and infections, Menopause Astragalus (Astragalus membranaceus) – Root Acyclovir20 Drugs incompatible with herb   Aldesleukin20 Astragalus with low dose Aldesleukin resulted in a 10-fold potentiation of Aldesleukin’s tumor cell killing activity with decreased side effects   Anticoagulants/Antiplatelet20 Increases risk of bleeding Remedies: Alzheimer’s, Common cold, Sore throat, Chemotherapy support Basil (Ocimum basilicum) – Leaf Antidiabetic agents5 May enhance hypoglycemic effects   Insulin5 May enhance hypoglycemic effects   Sulfonylureas5 May enhance hypoglycemic effects Remedies: Digestion, Stomach cramps, Vomiting, Constipation, Anxiety, Headaches Bay (Laurus nobilis) – Leaf Insulin5 Herb enhances hypoglycemic actions – may increase insulin’s effect more than three fold5 Remedies: Stomach problems, Rheumatism Bearberry Uva Ursi (Arctostaphylos uva-ursi) – Leaf Drugs that acidify the urine3,4,5,7 
e.g. Vita. C (Absorbic Acid) May decrease the urinary antimicrobial action   Drugs known to interact with hydroquinone2 Theoretically, caution should be exercised   Diuretics5 Enhances electrolyte loss Remedies: Arthritis, Urinary problems, Diarrhea, Bronchitis, Fever, Hemorrhoids Bee Pollen Antidiabetic agents5
Hypoglycemic agents5
Insulin5 Interact – May promote hyperglycemia Bilberry (Vaccinium myrtillus) – Fruit Anticoagulants5
e.g. Warfarin4,20 Increases risk of bleeding
Increases bleeding time   ASA4 Interact Bilberry – Leaves Insulin3 May cause hypoglycemia Remedies: Prevent cataracts, Enhance night vision, Blood circulation, Diarrhea, Liver & stomach problems Birch (Betula) – Leaf None reported5,10   Remedies: Lessens inflammation, Diuretic, Joint pain, Urinary tract infections Black Cohosh (Actaea racemosa) – Root Antihypertensives5 Increases hypotensive effects   Estrogen7,12 Interact   Hormone treatments14 Interact   Tamoxifen4 Augments antiproliferative action (in vitro) Remedies: PMS, Menstruation problems, Hot flashes Black Walnut (Juglans nigra) – Bark, leaf hull Atropine23 Interact   Codeine23 Decreased absorption Remedies: Candida, Skin problems Blue Cohosh (Caulophyllum thalictroides) – Root Angina therapy4,5,9 Interact   Antihypertensives5 Decreases effect of drug, increases blood pressure   Nicotine5 Increases effects of nicotine Remedies: Muscle spasms, Menstrual disorders, Nervous & memory disorders Borage (Borago officinalis) – Seed Oil Epileptogenic drugs20 May manifest seizures (theoretical)   Phenothiazines9 Interact Remedies: Skin & nail health Broom (Cytisus scoparius) – Aerial parts MAOIs23 Contains tyramine   Beta blockers5 Potentiates drug   Antihypertensives5 Interact Remedies: Diuretic, Emetic, Purgative Bugleweed (Lycopus spp) – Aerial parts Thyroid therapy23 Interact   Beta blockers5 May mask symptoms Remedies: Hyperthyroidism, Mood, Overactive heart Bupleurum (Bupleurum spp) – Root Interferon23 May lead to serious lung disease Remedies: Liver disease, Hemorrhoids, Digestion

Burdock (Arctium lappa) 
– Fruit & Roots

Oral hypoglycemics2,4,5,9 Increases hypoglycemia   Insulin3,5 Hypoglycemic effect – Leaves Oral hypoglycemics4 Increases hypoglycemia Remedies: Acne, Psoriasis, Rheumatoid arthritis Calendula (Calendula officinalis) – Flowers Hexobarbital2,3 Extends duration of drug action (rats) Remedies: Eczema, Gastritis, Sunburn, Minor burns and wounds Catnip (Nepeta cataria) – Aerial parts Dextromethorphan23 Potentiates effect of drug Remedies: Sedation, Colic Cat’s Claw (Uncaria tomentosa) – Root Bark Anticoagulants5 Potentiates effect of drug   Antihypertensives5 Potentiates effect of drug   Oral contraceptives4 May antagonize effect of drug   Hormone replacement therapy4,7 May antagonize effect of drug   Immunosuppressives4 May antagonize effect of drug   Insulins7 Interact   Ulcer medications10 Interact   Vaccines7 Interact Remedies: Stimulates immune system (taken by HIV and cancer patients), Rheumatism, Gastric, Ulcers, Tumors & Dysentery Cayenne Pepper (Capsicum frutescens) – Fruit All Drugs2 Increases hepatic metabolism   Antihypertensives2,5,9 Interact   ACE Inhibitors3,16 May increase cough   Centrally acting adrenergic agents5
e.g. Clonidine, Methyldopa5 Decreases effect of drug   Hexobarbital3 Increases plasma concentration and sleep with acute use and decreases with chronic use (rats)   MAOI2,5,9 Interact, hypertensive crisis   Theophylline3,16 Increases absorption and bioavailability of drug Remedies: Digestion, Blood circulation, Arthritis, Colds, Sore throat, Sinus problems Chamomile, German (Matricaria recutita) – flowers All Drugs5 Decreases absorption of drugs secondary to Chamomile 
Antispasmodic activity in GI tract   Anticoagulants5,9 Large doses of herb may interact Remedies: Digestion, Diuretic, Sleep aid, Colitis, Diverticulosis, Fever, Headaches, Stress Chaparral (Larrea tridentata) – Aerial Parts Anticoagulants20 Chaparral has been shown to interact with platelet adhesion and aggregation in aspirin-treated patients   Barbiturates4 Inhibits metabolism   MAOIs9 Excessive doses of Chaparral may interact with MAOI therapy Remedies: Diuretic, Laxative w Chasteberry (Vitex agnus-castus) – Berry Dopamine-receptor antagonists1,4,13 
e.g. Antipsychotics & Metoclopramide14 Decreases therapeutic effect of drug (animal)   Dopaminergic drugs Interact   Hormone therapy4 Interact   Oral contraceptives3,4 Interact with efficacy of drug Remedies: Colds, Coughs Chondroitin sulfate Anticoagulants5 Potentiates effects of drug Remedies: Joint health, Arthritis Cinnamon (Cinnamomum Zeylanicum) – Bark None reported1,5   Remedies: Diarrhea, Nausea, Blood circulation, Fungal infection, Digestion Cloves (Syzgium aromaticum) – Buds Anticoagulants9 Potentiates anticoagulant effects of drug Remedies: Antiseptic, Anti parasitic, Digestive aid, Dental problems Coltsfoot (Tussilago farfara) – Leaf Antihypertensives4,5,9 Interact   Cardiovascular therapy4,9 Interact Remedies: Coughs, Respiratory ailments, Diabetes Comfrey (Symphytum officinale) – Leaf or Root None reported4,5   Remedies: Wounds and many skin problems Cranberry (Vaccinium macrocarpon) – Berry Renally excreted drugs5 May increase elimination of some drugs excreted in the urine. Remedies: Urinary tract infections Dandelion (Taraxacum officinale) – Root Antidiabetic agents5,9 May potentiate effect of drug, promoting hypoglycemia   Antihypertensives5 Additive or synergistic hypotensive effect   Lithium3,4 Toxic effect of lithium worsened – Leaf Diuretics2,4,5,9 Potentiates the diuretic action of drug (Herb is rich in potassium) Remedies: Constipation, Indigestion, Water retention, Alcoholism Devil’s Claw (Harpagophytum procumbens) – Root Cardiac therapy2,9 Interact   Antiarrhythmic drugs2,4,5 Theoretical possibility of interaction due to herb’s protective action against arrhythmia   Hypo/hypertensive therapy2,9 Interact   Warfarin16 Increases risk of Purpura Remedies: Indigestion, Heartburn and Arthritis Dong Quai (Angelica sinensis) – Root Anticoagulants2,5,12 Interact   ASA12 Interact   Warfarin4,20 Herb may enhance the anticoagulant effect of drug   HRT – Hormone Therapy22 Interact Remedies: Breast cysts, Menopause and PMS symptoms Echinacea (Echinacea species) – Root/Leaf Cancer treatments4 Herb stimulated immune system   Econazole nitrate cream3 Recurrence rate of vaginal candida infection decreases when the herb juice is used simultaneously   Immunosuppressive agents2,4,9
e.g. Corticosteroids & Cyclosporine4 Herb stimulates immune system   Hepatotoxic drugs12 Increases liver toxicity with other hepatotoxic drugs   Warfarin4 Increases bleeding time (anecdotal reports) Remedies: Boost immune system to prevent colds, flu, ear infections, sore throats, mouth ulcers (cankers), gingivitis and yeast infections Elder (Sambucus nigra) – Berry None reported1,2,5,10   Remedies: Colds, Herpes simplex, Sore throat, Flu, Inflammation Evening Primrose Oil (Oenothera biennis) – Seed Anticoagulants2,14,20 Interact, may reduce platelet aggregation and potentiate drug action   Beta-blockers2,14 Decreases action of herb   Corticosteroids2,14 Theoretically interact   Epileptogenic drugs2,4,9 
e.g. Phenothiazines2,5,9,14,19 Increases epileptic attacks   Lithium carbonate2 Decreases neurotoxicity   NSAIDs2,14 Theoretically interact   Vasodilators20 May potentiate effect of drug Remedies: Arteriosclerosis, Diabetes, Eczema, Fibrocystic breast disease, PMS, Rheumatoid arthritis Fenugreek (Trigonella foenumgraecum) – Seed All Drugs3,5,9,20 Absorption of all drugs may be affected due to mucilaginous fiber content and high viscosity in gut   Anticoagulants5,9,10 Interact   Heart medications10 Interact   Hormonal therapy9,10 Interact   Hypoglycemic therapy5,9 Interact   Insulin3,20 Dose may need adjustment due to hypoglycemic activity   MAOIs9,10 Interact Remedies: Lowering cholesterol and triglyceride levels, Diabetes, Arteriosclerosis Feverfew (Tanacetum parthenium) – Leaf Anticoagulants2,4,12,13
e.g. Warfarin2,4 Potentiates effect of drug   Aspirin12,13 Increases antithrombotic effect   Corticosteroids2 Decreases effect of herb   Imitrex12 Decreases efficacy of drug   NSAIDs2,12 Decreases effect of herb   Tylenol12 Decreases efficacy of drug Remedies: Migraines Flax (Linum usitatissimum) – Seed All Drugs1,3,4,5,13,20 Absorption of drug delayed when herb used as a bulk laxative   Insulin21 Potentiates effect of drug due to delayed absorption of glucose   Laxatives5 Increase in laxative actions of flax   NSAIDs4
e.g. Indomethacin4 Increases prevalence of stomach/intestinal ulcers Remedies: Bone, Nail, Teeth, Skin health Forskohlii (Coleus forskohlii) – Root Clonidine23 Potential interaction Remedies: Allergies, Asthma, Eczema, Irritable bowel syndrome, Menstrual cramps, High blood pressure, Glaucoma

Herb Drug Class Type of Interaction Garlic (Allium sativum) – Bulb Anticoagulants2,4,5,7,9,19
e.g. Warfarin1,3,11,12,16,19,20 Interact   Antiplatelet therapy5 Anticoagulant activity of drug enhances (may double clotting time)   ASA2,9,12 Enhances effects of antiplatelet therapy
Potentiates the anti-thrombotic effect of ASA   Diabetic Therapy2,9
e.g. Insulin3 Dose of drug may need adjusting due to hypoglycemic effects of herb Remedies: Cardiovascular system, Congestive heart failure, Lowering cholesterol and triglyceride levels Ginger (Zingiber officinale) – Root All drugs3 Increases absorption of drug   Anticoagulants2,4,5,9,11,19,20 Inhibitory effect on thromboxane synthesis   Cardiac therapy2,9
Interact   Cyclophosphamide3 Side effect of vomiting prevented by prior administration of acetone extract of ginger or its component 6-gingerol (PO in Suncus/shrew)   Diabetic therapy2,9
Interact   Sulfaguanidine3,4 Increases absorption of drug (rats) Remedies: Anti-nausea, Anti-vomiting, Blood circulation, Indigestion Ginkgo (Ginkgo biloba) – Leaf Anticoagulants1,2,4,5,12,13,14,19 
& Antiplatelet therapy20 Potentiates effect of drug – Monitor coagulation   e.g. Aspirin3,12,16,20 
NSAIDs4 Warfarin16,20 
Ticlopidine20 May introduce spontaneous bleeding
Interact
Potentiates effect of drug   MAOIs3,20
May potentiate effects of drug   Papaverine3 Potentiates effect of intracavernosal injection for impotence (in 20% of patients for whom previously ineffective)   SSRIs20
Ginkgo may counter the sexual dysfunction that may be experienced with SSRIs   Thiazide diuretic18 Herb decreases effect of drug, the interaction causes hypertension Remedies: Alzheimer’s disease, Blood circulatory diseases, Depression, Diabetes, Male impotence, Migraine, Multiple sclerosis, Tinnitus Ginseng North American (Panax quinquefolius) – Root Anticoagulation therapy3,4,12,16 
e.g. Warfarin20 Interact
Decreases INR levels   Antihypertensives4 
e.g. Diuretics20 Interact
Decreases diuretic action   Digitalis12
Increases toxicity   Estrogen Therapy4,9 Interact   Oral Hypoglycemia therapy4,5
Interact   Insulin3 Dose adjustment due to hypoglycemic effect   MAOIs1,3.4.5.9.11.12.20 Interact   Oral contraceptives12 Interact   Psychotherapeutic medication4,12/Antipsychotics19 
e.g. Phenelzine4,9,16,20 Interact   Steroids12,19 Interact Remedies: Flu, Common cold, Sore throat, Chronic fatigue syndrome, Fibromyalgia, Alzheimer’s disease, Arteriosclerosis, 
Chemotherapy support, Male reproductive health, Stress, Diabetes Ginseng Siberian (Eleuthero coccus senticosus) – Root Anticoagulants2,4 Interact   Antipsychotics4,9 Interact (Stimulant activity)   Barbiturates2,4
e.g. Hexobarbital3,5 Potentiates effects of drug
Increases effect of drug due to inhibition of its metabolic breakdown   Cardiac therapy2,9 Interact   Diabetes therapy2,4,9 Interact   Digoxin2,5,16,19 Increases serum digoxin levels   Estrogen4 Potentiates effect of drug   Hypertension therapy2,4 Contra-indicated   Hypotension therapy2,9 Interact   Insulin3 May need to adjust dose due to hypoglycemic effect   Monomycin & Kanamycin3 Increases efficacy in treating Shigella dysentery and Proteus enterocolitis probably due to enhancement of t-lymphocyte activity Remedies: Alzheimer’s disease, Attention deficit disorder, Adjunctive chemotherapy, Chronic fatigue syndrome, Common cold, Diabetes, Flu, Fibromyalgia, Stress Glucosamine Sulfate (2-Amino-2-deoxyglucose) Diabetic medication15 Causes a decrease in insulin secretion and in insulin sensitivity (in animal studies) Remedies: Arthritis, Joint pain Goldenseal (Hydrastis canadensis) – Root Anticoagulants4,5,9 Potential interaction   Antihypertensives5
e.g. Beta blockers5
Calcium channel blockers5 Increases effect of drug   Barbiturates2,4
e.g. Barbitu Increases sleeping times (rats)   Cardiovascular medications4
e.g. Digoxin5 Interact
Increases effect of drug   CNS depressants5
e.g. Alcohol, benzodiazepines5 Enhances sedative effects   Oral Hypoglycemia Therapy22 Herb lowers blood sugar levels Remedies: Common cold, Chronic ear infections, Urinary tract infections, Crohn’s disease Grapefruit (Citrus paradisi) – Fruit/Juice All Drugs including: 
Benzodiazepines3,18
e.g. Midazolam, triazolam, alprazolam18, Buspirone18 Increases bioavailability
Inhibits metabolism by cytochrome P450-3A enzymes   Calcium Antagonists3,18
e.g. Amlodipine, verapamil, nisoldipine, nifedipine, nitrendipine, felodipine, nimodipine, nicardipine     Carvedilol18     Cisapride18     Clomipramine18     Coumarin3     Cyclosporin3,18     Ethinyl estradiol3,18     HMG CoA reductase inhibitors18 
e.g. Atorvastatin, cerivastatin, lovastatin, simvastatin18     Saquinavir18     Tacrolimus18     Terfenadine3   Remedies: Appetite stimulant, Digestion, Diuretic Grape Seed Extract None reported5   Remedies: Good nutritional value Green Tea (Camellia sinensis) – Leaf All Drugs Green Tea has similar interactions as occur with caffeine   Calcium12 Decreases absorption of calcium   Doxorubicin5 May enhance the antitumor activity of doxorubicin Remedies: Stimulates immune system, Infections, Gum disease, some cancer risk reduction, Lowers cholesterol level, High blood pressure, High triglyceride levels Hawthorn (Crataegus laevigata) – Aerial parts Antihypertensives5 Increases hypotension   Cardiac glycosides3,5,12,19 
e.g. Digitoxin, Digoxin3, Digitalis1,3,4 Potentiates effect of drug (helps lower digoxin levels where toxicity is a concern)   Cardiac medications7,9 
e.g. Nitrates5 Interact
Increases hypotension   CNS depressants5 Addictive effects Remedies: Angina, Arteriosclerosis, High blood pressure Hops (Humulus lupulus) – Strobiles Alcohol2,9,14,20 Potentiates action of alcohol   CNS depressants5 Increases effect of drug   Cytochrome P450 metabolized drugs2,5 Yet to be evaluated   Pentobarbital3 Increases sleeping time (mice)   Phenothiazine-type antipsychotics5 Combination of herb and drug increases hyperthermia   Sedative-hypnotics2,9,14,20 Potentiates effect of drug Remedies: Anxiety, Insomnia Horse Chestnut (Aesculus hippocastanum) – Seed Anticoagulants3,5
ASA3,5 Increased risk of bleeding Remedies: Varicose veins, Hemorrhoids, Blood circulation Horseradish (Armoracia rusticana) – Root Thyroid medications9 Interact Remedies: Coughs, Diuretic, Sinus, Throat and lung problems Juniper (Juniperus communis) – Berry Diuretic therapy2,9 Potentiates effect of drug   Hypoglycemic therapy2,9 Potentiates effect of drug Remedies: Urinary tract infections, water retention Kava (Piper methysticum) – Root Alcohol1,2,3,5,7,12,14 Potentiates action of herb   Anticoagulants19 Interact   Antidepressants7,12 Interact   Antipsychotics7 Interact   Barbiturates1,2,4,5,7
e.g. Hexobarbital2
e.g. Pentobarbital3,5 Potentiates action of barbiturates
Potentiates effect of drug (animals)
Potentiates effect of drug   Benzodiazepines2,3,4,12,14,19/Tranquillizers12
e.g. Alprazolam2,5,20 Potential interaction
Potentiates effect of drug   Centrally acting drugs1,2,4,7,20 Potentiates effect of drug   CNS depressants3,5 Potentiates effect of drug   Levodopa3 Decreases efficacy   Hepato toxic drugs Potentiates effect of drug Remedies: Anxiety Lemon Balm (Melissa officinalis) – Leaf CNS depressants14 Interact   Hexobarbital3 Enhances effect of drug   Pentobarbital2,3,4 Promotes hypnotic action (mice)   Thyroid medications2,4,14 Interact Remedies: Herpes simplex, Indigestion, Insomnia, Nerve pain, Hyperthyroidism Licorice (Glycyrrhiza glabra) – Root

Agents that prolong the QT interval5
e.g. procainamide, quinidine, terfenadine5

May prolong the QT interval   Antihypertensives4,5,12 Interact   Aspirin3,20 Deglycyrrhizinated licorice decreases ulcer formation (rats) & gave greater protection from ASA-induced gastric mucosal damage when used with cimetidine (rats)   Cardiac glycosides2,3,11
e.g. Digitalis1,3,12,20
Digoxin5 Affect potassium levels
Increases toxicity due to decreases in potassium   Cardiovascular drugs4 Interact   Cathartics4
e.g. Stimulant laxatives3 Interact
Additive effect – increases potassium loss   Corticosteroids3,4,5,11,20
e.g. Hydrocortisone2,3,16,
Prednisolone2,16 Interact
Potentiates effect of drug 
Inhibit metabolism, increases plasma concentration   Diuretics3,4,5,11,12,20
e.g. Loop diuretics2,11,
Potassium-sparing diuretics2,
Potassium-excreting agents or amiloride4, Spironolactone3,4,5,11,
Thiazide1,3,11 Affects potassium, potentiates potassium depletion   Hormonal therapy4,9
e.g. Oral contraceptives16 Interact
Hypertension, edema, hypokalemia   Estrogen & antiestrogen2 Interact   Insulin2,3,4,9 Increases electrolyte disturbances   Nitrofurantoin2 Increases bioavailability Remedies: Asthma, Bronchitis, Canker sores, Eczema, Herpes simplex, Indigestion, Heartburn, Peptic ulcer, Chronic fatigue syndrome Lobelia (Lobelia inflata) – Aerial parts Nicotine therapy5 (smoking cessation treatments) Contra-indicated – Nicotine and Lobelin are chemically similar in structure Remedies: Coughs, Colds, Asthma, Bronchitis, Flu, cardiovascular, Epilepsy

Herb Drug Class Type of Interaction Ma Huang (Ephedra sinica) – Aerial parts All Drugs2 Herb has similar interactions to those occurring with Ephedrine   Anesthetics4 Interact   Agents that influence urine pH
e.g. Antacids3,4
Acetazolamide20 Interact

Acetazolamide may cause increased concentration of ephedrine due to alkalinization of the urine   ASA4 Potentiates effect of drug   B adrenergic blockers4,5 Interact   Cardiac glycosides1,4,11,13
e.g. Digitoxin7 Disturb heart rhythm 
Interact   Corticosteroids2
e.g. Dexamethasone3 Interact
Increases clearance and thereby reduces effect   Centrally acting medications2,4
e.g. Antidepressants2
Antihypertensives2,4
Clonidine20 Interact
Interact
Interact
Clonidine may augment the pressor response to ephedrine   Ephedra alkaloids5 Hypertensive crisis   Ergot alkaloid derivatives11 Interact   Guanethidine1,2,4,7,11,13,20 Increases sympathomimetic effect   Halothane1,2,11,13,20 Disturbs heart rhythm   MAOIs1,2,3,4,7,11,13
e.g. Tranylcypromine, selegiline, phenelzine, moclobemide3, isocarboxazid20 Increases sympathomimetic effect
Severe hypertension   Methyl Xanthines3
e.g. Theophylline2,3,4,5,20 Interact, increases side effect (GI and CNS) of both herb and drug   Oxytocin1,2,4,11,13 Hypertension   Phenothiazine5 Hypotension   Reserpine3,20 Indirect sympathomimetic effects of ephedrine are antagonized   Secale alkaloid derivatives1,2 Hypertension   Sodium Bicarbonate20 Ephedrine toxicity increases due to decreased elimination   Stimulants2 Interact   Sympathomimetic agents4,20 Interact Remedies: Breathing problems, Asthma, Nasal congestion Marshmallow (Althaea officinalis) – Root All Drugs1,3,4,5,10 Delays absorption of drug   Dexamethasone4 Potentiates effect of drug   Hypoglycemic therapy9,10 Interact   Insulin5 Increases hypoglycemic effects   Sulfonylureas5 Increases hypoglycemic effects Remedies: Peptic ulcer, Crohn’s disease, Diarrhea, Asthma, Common cold, Sore throat Meadowsweet (Filipendula ulmaria) – Leaf/Flower All Drugs2,9

e.g. Anticoagulants2 Herb has similar interactions to those occurring with salicylates
Interact Remedies: Diarrhea, Stomach problems Milk Thistle (Silybum marianum) – Seed All Drugs2 Increases live metabolism of all drugs   Acetaminophen4,19 Reduces hepatotoxicity   ASA3,4 Altered metabolism in people with liver cirrhosis might be improved   Butyrophenones20 Reduces lipid peroxidation   Carbon tetrachloride4,19 Reduces hepatotoxicity   Cisplatin3,4 Reduces hepatotoxicity   Cyclosporine4 Reduces hepatotoxicity
Synergistic antiproliferative effect on human ovarian and breast cancer cell lines   Doxorubicin4 Synergistic antiproliferative effect on human ovarian/breast cancer cell lines   Ethanol4,19 Reduces hepatotoxicity   Iron4 Reduces hepatotoxicity   Phenothiazines4,20 Reduces hepatotoxicity   Phenytoin21 Reduces hepatotoxicity Remedies: Gallstones, Psoriasis, Liver health Mistletoe (Viscum album) – Aerial parts Anticoagulant therapies9 Interact   Antihypertensives4,5,10 Increases hypotensive effects/check blood pressure regularly   Antidepressants9,10 Interact   Cardiac drug5,9,10 Increases cardiac depression   Coagulant therapies9 Interact   CNS depressants5 Increases sedative effects   Hypotensive therapies9 Interact   Immunosuppressants5,9 Cytotoxic and immunostimulant effects   MAOIs4 Interact/monitor Remedies: Blood pressure and heart, Mood, Migraine Nettle (Urtica dioica) – Leaf Anticoagulants4/
Coagulant therapy4 Interact   Antihypertensives2,4,9 Interact   CNS depressants4,9 Potentiates effect of drug   Diabetic medication2,4,9 Interact   Diclofenac (low dose)3,4 Leaf extract enhances the inflammatory response effect of diclofenac
Potentiates effect of drug   Diuretics2,5 Potentiates effect of drug   Hypotension medication4,9 Interact – Root Prostatic Hyperplasia Therapy22
e.g. Tamsulosin Potentiates effect of drug Remedies: BPH (enlarged prostate), hay fever Passionflower (Passiflora incarnata) – Leaf Barbiturates4
e.g. Hexobarbital, Pentobarbital2,3 Increases hypnotic action
Increases sleeping time (animal)   Centrally Acting Medications2,4,5 Increases hypnotic action and potential for monoamine oxidase inhibition   CNS depressants20 Potential for additive effects and increases sedation   MAOI Antidepressants5,7,9 Interact Remedies: Anxiety, Insomnia Pau D’arco (Tabebuia impetiginosa) – Bark Anticoagulants5,20 May potentiate effects of drug, prolongation of prothrombin time20   Iron5 Decreases absorption of iron Remedies: Infections and yeast infections Peppermint (Mentha x piperita) – Leaf Ulcer treatment e.g. H2
Receptor Blockers May antagonize achlorhydria Remedies: Migraine, Nerves, Stomach disorder, Heartburn, Herpes, Abdominal cramps Pine Bark Extract (Pinus maritima) None reported4,5   Remedies: Chronic venous insufficiency Propolis
– Resin Tetracycline24 Increases effectiveness Remedies: Anemia, Skin healing, Respiratory problems, Immune system support, Digestion Psyllium (Plantago psyllium)
– Seed All drugs1,3 May delay absorption of drugs   Anti-coagulants21 Delays absorption of drug   Anti-convulsants
e.g. Carbamazepine5,20 Decreases absorption and concentration of drug   Cardioactive drug5
e.g. Beta blockers, calcium channel blockers, digitalis5 A possibility that the herb enhances digitalis effect of the drug (highly speculative)   Insulin3 Drug dosage must be adjusted due to slowing of dietary carbohydrate absorption   Lithium3,5,16 Decreases concentration due to reduction of drug absorption Remedies: Constipation, Diarrhea, Hemorrhoids, Irritable bowel syndrome, Obesity, Arteriosclerosis, High cholesterol, High triglyceride level, Psoriasis Puncture Vine (Tribulus terrestris) None reported4   Remedies: Vitiligo (whitening of skin), Impotence, Female infertility, Urinary problems Pygeum (Prunus africana) – Bark Antibiotics for prostate and bladder infections4 Enhances effectiveness of drug Remedies: Urinary problems, Enlarged prostate Red Clover (Trifolium pratense) – Blossoms Anticoagulants5,9,10
e.g. Heparin, Warfarin5 May increase risk of bleeding   Antiplatelet agents5
e.g. ASA, clopidogrel, ticlopidine5 May increase risk of bleeding   Hormone Replacement Therapy9,10 Interact   Oral Contraceptive5,9,10 May enhance action of drug by increasing estrogen components Remedies: Coughs Eczema, Possible cancer reduction Red Raspberry (Rubus idaeus) – Leaf Antidiabetic agents5,9 Increases effectiveness of hypoglycemic action Remedies: Menstrual problems, Diarrhea, Canker sores Red Yeast Rice lovastatin23 
Simvastatin23 
Atorvastatin23 Additive effect similar in (Cholestin) Remedies: Lowering cholesterol levels Rose Hips (Rosa canina) None reported5   Remedies: Colds, Infection Rosemary (Rosmarinus officinalis) – Leaf Disulfiram5 Disulfiram reaction if herbal product contains alcohol Remedies: Circulatory system, Heart problems, High blood pressure, Menstruation Royal Jelly Antidiabetic agents5 May lead to loss of glycemic control in diabetic patients Remedies: Appetite stimulant, Chronic fatigue syndrome, Liver disease, Insomnia, Multiple sclerosis

Herb Drug Class Type of Interaction Sage (Salvia officinalis) – Leaf Anticonvulsants5,9 Lowers seizure threshold   Antidiabetic agents5,9
e.g. Insulin5 Antagonizes glycemic control   Sedatives9 Herb may potentiate sedative effects of other drugs Remedies: Menopause, Tonsillitis, Fever Saw Palmetto (Serenoa repens) – Berry Hormone replacement therapy2,4,9 Interacts because of its anti-androgen and estrogenic activity   Oral contraceptives2,4,9 Interacts because of its anti-androgen and estrogenic activity Remedies: BPH (enlarged prostate) Schisandra (S. chinensis) – Berry Acetaminophen23 Reduces hepatotoxicity Remedies: Coughs, Asthma, Urinary problems, Tonic Scullcap (Scutellaria lateriflora) – Aerial parts Centrally-acting medications2 Potentiates effect of drug   Sedatives and tranquillizers3,4 Interact Remedies: Infertility, Nerve disorders Scullcap, Chinese (Scutellaria baicalensis) – Root Immunosuppressives5 Possible interaction   Platelet aggregation inhibitors3,4 Potentiates effect of drug   Senna (Cassia spp) – Leaf, Pod Indomethacin5 Decreases drug levels   Calcium channel blockers5 Potentiates potassium depletion   Digoxin23 Interacts Remedies: Sore throat, Fevers, Heart problems Slippery Elm (Ulmus rubra) – Aerial parts All Drugs7 May interfere with the absorption of drugs taken simultaneously Remedies: Gastritis, Crohn’s disease, Cough, Common cold, Sore throat St. John’s Wort (Hypericum perforatum) – Aerial parts All Drugs21,22 Drugs metabolized by cytochrome P450 3A4 enzyme system have potential to interact   Antabuse12 Interact   Antidepressants4,5,12,17
e.g. Trazodone
nefazodone16,17
see MAOIs & SSRIs below Serotonin syndrome   Anti-epilepsy drugs17
e.g. Phenytoin
carbamazepine
phenobarbital17 Interact   Anti-retroviral drugs
e.g. Indinavir Interact   Atypical antipsychotics12
e.g. Olanzapine, risperidone12 Interact   Beta2 agonists12 Interact   Dextromethorphan2,12 Interact   Dibenzazepine Derivatives2
e.g. Amitriptyline, doxepin, carbamazepine2 Interact   Digoxin5,16,17 Interact   Dopamine agonists12 Interact   Immunosuppressants17
e.g. Cyclosporine16,17,20 Interact – Decreases cyclosporine plasma concentration20   Meperidine2 Interact   Metronidazole12
Midodrine20 Interact
Enhances pressor effect   Migraine therapies17 Interact   Monoamine Oxidase Inhibitors (MAOIs)2,3,5,9,12,20
e.g. Phenelzine, tranylcypromine, isocarboxazid Interact   Narcotics5
e.g. Morphine2 Interact   Oral Contraceptives16,17 Interact – can make ineffective   Reserpine3 Decreases effect of drug (mice)   Selective Serotonin Reuptake Inhibitors (SSRIs)2,3,4,5,7,12,16,17,20
e.g. Fluoxetine, paroxetine5, sertraline Serotonin syndrome   Sympathomimetics2,5,12
e.g. Ephedrine, methyldopa, dopamine, tryptophan Interact   Theophylline4,12,16,17,20 Interact   Tyramine containing foods2,5 Decreases theophylline level
Interact (speculative)   Warfarin17 Interact Remedies: Depression, Vitiligo (whitening of skin), Recurrent ear infections Tea Tree Oil (Melaleuca alternifolia) – Leaf None reported2,4,5,12   Remedies: Yeast infection, Vaginitis, Athletes foot, Acne Thyme (Thymus vulgaris) – Leaf & Flower None reported1,2,5   Remedies: Digestion, Fever, Headache, High cholesterol, Skin problems Turkey Tail (Coriolus versicolor) Cyclophosphamide23 Cyclophosphamide23 Remedies: Respiratory problems, Mood, Tonic Tumeric (Curcuma longa) – Root Anticoagulants5 Additive effects on platelets   Immunosuppressants5 Decreases effects of drug   NSAIDs5 Inhibits platelet function and increases risk of bleeding   Reserpine and indomethacin3 Tumeric root solid alcoholic extract reduces the frequency of gastric and duodenal ulcer (rats) Remedies: Bursitis, Rheumatoid arthritis, Liver health, Arteriosclerosis Uva Ursi see Bearberry     Remedies: Urinary tract infection Valerian (Valeriana officinalis) – Root Alcohol5,11,16 Potentiates effects of alcohol   Anticonvulsants12 Increases seizures   Barbiturates19
e.g. Pentobarbital, thiobarbital3 Increases sleeping time   Benzodiazepines3,19
e.g. Diazepam3 May be helpful in withdrawal from benzodiazepines   CNS depressants2,5,14,19 Potentiates effects of drug   Sedative medications4,9,11,12,14 Potentiates effects of drug Remedies: Insomnia Wild Yam (Dioscorea villosa) – Root Oral Contraceptive22 Interact – may interfere with effectiveness of contraceptive Remedies: High cholesterol, High triglyceride levels, Abdominal cramps, Menopause, Muscle pain and spasms Willow (Salix) – Bark All Drugs1,2,9 Willow has similar interaction to those occurring with salicylates. Irreversible inhibition of platelet aggregation by aspirin cannot be induced by structurally different salicin21   Anticoagulants5,9 Increases bleeding   Antihypertensives5 Reduces effect   Diuretics5 Increases risk of salicylate toxicity (highly speculative)   Methotrexate9 Interact   Metoclopramide9 Interact   NSAIDs5,13 Interact   Phenytoin9 Interact   Probenecid9 Interact   Salicylates9,13 Interact (no cases reported)   Spironolactone9 Interact   Valproate9 Interact Remedies: Headache, Pain, Backache, Nerve pain, Toothache Yarrow (Achillea millefolium) – Aerial parts Antacids4 Interact   Anticoagulant therapy4,5,9 Interact   CNS depressants5 Increases sedation   Diuretics4 Interact   H2receptor antagonists4 Interact   Hypertensive4,5,9 / Hypotensive therapy4,9 Interact   Sedatives4 Interact Remedies: Inflammation, Improves blood clotting, Diuretic, Fever, Some inflammatory disorders Yohimbe (Pausinystalia yohimbe) – Bark a-adrenoceptor blocking agents3
e.g. Phenoxybenzamine, phentolamine3 Increases toxicity of yohimbine   Amobarbital3 Interact   Antidepressants5,7,20 Interact   Atropine3 Interact   Beta blockers3
e.g. Propranolol, penbutolol, metoprolol3 Protects against yohimbine toxicity (mice)   Central a2-adrenergic agonists3
e.g. Guanabenz, a-methylnorepinephrine3 Reverses hypotensive effects   Clonidine3 Reverses hypotensive effects   Hypotensive drugs1,20 Potentiates   MAOIs1,3,20 Potentiates   Naloxone3,20 Affects synergistically enhances   Phenothiazines3
e.g. Chlorpromazine, promazine3 Increases toxicity of yohimbine   Reserpine3 Interact   Sedatives3 Increases effect of drug   SSRIs5 Increases stimulation   Sympathomimetics3,5,10
e.g. Epinephrine, ephedrine, amphetamine, cocaine3 Increases toxicity of yohimbine   Thioxanthenes3
e.g. Chlorprothixene3 Increases toxicity of yohimbine   Tricyclic anti-depressants3,5,16
e.g. Clomipramine3,20, imipramine, amitriptyline3 Combination of herb and drug may cause hypertension
Lower doses of yohimbine may have favorable effect in orthostatic hypotension induced by tricyclic anti-depressants   Tyramine containing foods5,20 Increases blood pressure Remedies: Depression, Male impotence

References

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2. Boon, Heather, & Smith, Michael. (1999). The botanical pharmacy: The pharmacology of 47 common herbs. Kingston, ON: Quarry Press Inc.
3. Brinker, Francis. (1998). Herb contraindications and drug interactions: With appendices addressing specific conditions and medicines (2nd ed.). Sandy, OR: Eclectic Medical Publications.
4. Chandler, Frank. (Ed.). (2000). Herbs: Everyday reference for health professional. Ottawa, ON: Canadian Pharmacists Association and the Canadian Medical Association.
5. Fetrow, Charles W., & Avila, Juan R. (1999). Professional’s handbook of complementary and alternative medicines. Springhouse, PA: Springhouse Corp.
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