Herbal & Drug Interactions


This list below provides common herbal and drug interactions.

Please note that the prescription drug listings are not all-inclusive; drugs listed
are common examples.

If you are currently on any of the following drugs below, you need to exercise extreme caution if you are using any of the herbal or nutraceutical's that are listed below.

For example, if you are currently on a statin drug (such as: lipitor) you should not be taking red yeast rice, the reason for this is that red yeast rice is also very effective for lowering cholesterol levels.

By taking both a statin drug and red yeast rice, this in most cases will lower your cholesterol levels to much. This would be similar as if your medical physician was giving you twice the dosage of the statin drug.

The extensive background, qualifications and education that Dr. Hardy has undergone, as both a Certified Clinical Nutritionist (CCN) and Diplomate of the American Clinical Board of Nutrition (DACBN) Dr. Hardy can assist you in this area
of health care.

If you would like to use an integrative approach of using both medication and herbal / nutraceutical's, Dr. Hardy can help to monitor you with blood work to make sure you are not getting your levels in an unsafe range. 

If you prefer to use the herbal or nutraceutical approach, Dr. Hardy will monitor
your results and blood tests if needed,
to see if this option is safe and working for you.

Remedies: Nutritional support, retained water, Cholesterol, menopause, addiction,
urinary, bowel problems

Herb Drug Class Type of Interaction
Alfalfa (Medicago sativa) - Leaf Anticoagulants2,4,9
e.g. Warfarin3
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: Immune system, Cancer, Heartburn, Arthritis

Aloe Vera - (A. vera) Latex Powder All drugs12 Aloe latex will bind all drugs
  Antiarrythmic agents5,11,12 
e.g. Quinidine
  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
e.g. Loop diuretics5
e.g. Thiazide diuretics5,11
Increases potassium loss
  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: Digestion, Infection, Respiratory problems and infections, Menopause

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: Alzheimer's, Common cold, Sore throat, Chemotherapy support

Astragalus (Astragalus membranceus) - Root Acycloir20 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: Digestion, Stomach cramps, Vomiting, Constipation, Anxiety, Headaches

Basil (Ocimum basilicum) - Leaf Antidiabetic agents5 May enhance hypoglycemic effects
  Insulin5 May enhance hypoglycemic effects
  Sulfonylureas5 May enhance hypoglycemic effects

Remedies: Stomach problems, Rheumatism

Bay (Laurus nobilis) - Leaf Insulin5 Herb enhances hypoglycemic actions - may increase insulin's effect more than three fold5

Remedies: Arthritis, Urinary problems, Diarrhea, Bronchitis, Fever, Hemorrhoids

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: Prevent cataracts, Enhance night vision, Blood circulation, Diarrhea,
Liver & stomach problems

Bee Pollen Antidiabetic agents5
Hypoglycemic agents5
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: Lessens inflammation, Diuretic, Joint pain, Urinary tract infections

Birch (Betula) - Leaf None reported5,10  

Remedies: PMS, Menstruation problems, Hot flashes

Black Cohosh (Actaea racemosa) - Root Antihypertensives5 Increases hypotensive effects
  Estrogen7,12 Interact
  Hormone treatments14 Interact
  Tamoxifen4 Augments antiproliferative action (in vitro)

Remedies: Candida, Skin problems

Black Walnut (Juglans nigra) - Bark, leaf hull Atropine23 Interact
  Codeine23 Decreased absorption

Remedies: Muscle spasms, Menstrual disorders, Nervous & memory disorders

Blue Cohosh (Caulophyllum thalictroides) - Root Angina therapy4,5,9 Interact
  Antihypertensives5 Decreases effect of drug, increases blood pressure
  Nicotine5 Increases effects of nicotine

Remedies: Skin & nail health

Borage (Borago officinalis) - Seed Oil Epileptogenic drugs20 May manifest seizures (theoretical)
  Phenothiazines9 Interact

Remedies: Diuretic, Emetic, Purgative

Broom (Cytisus scoparius) - Aerial parts MAOIs23 Contains tyramine
  Beta blockers5 Potentiates drug
  Antihypertensives5 Interact

Remedies: Hyperthyroidism, Mood, Overactive heart

Bugleweed (Lycopus ssp) - Aerial parts Thyroid therapy23 Interact
  Beta blockers5 May mask symptoms

Remedies: Liver disease, Hemorrhoids, Digestion

Bupleurum (Bupleurum ssp) - Root Interferon23 May lead to serious lung disease

Remedies: Acne, Psoriasis, Rheumatoid arthritis

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 Hexobarbitol2,3 Extends duration of drug action (rats)

Remedies: Sedation, Colic

Catnip (Nepeta cataria) - Aerial parts Dextromethorphan23 Potentiates effect of drug

Remedies: Stimulates immune system (taken by HIV and cancer patients), Rheumatism, Gastric,
Ulcers, Tumors & Dysentery

Cat's Claw (Uncaria tomentosa) - Rootbark 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: Digestion, Blood circulation, Arthritis, Colds, Sore throat, Sinus problems

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, Diuretic, Sleep aid, Colitis, Diverticulosis, Fever, Headaches, Stress

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: Diuretic, Laxative

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: Colds, Coughs

Chasteberry (Vitex agnus-castus) - Berry Dopamine-receptor antagonists1,4,13 
e.g. Antipsychotics & Metaclopramide14
Decreases therapeutic effect of drug (animal)
  Dopaminergic drugs Interact
  Hormone therapy4 Interact
  Oral contraceptives3,4 Interact with efficacy of drug

Remedies: Joint health, Arthritis

Chondroitin sulfate Anticoagulants5 Potentiates effects of drug

Remedies: Diarrhea, Nausea, Blood circulation, Fungal infection, Digestion

Cinnamon (Cinnamomum Zeylanicum) - Bark None reported1,5  

Remedies: Antiseptic, Anti parasitic, Digestive aid, Dental problems

Cloves (Syzgium aromaticum) - Buds Anticoagulants9 Potentiates anticoagulant effects of drug

Remedies: Coughs, Respiratory ailments, Diabetes

Coltsfoot (Tussilago farfara) - Leaf Antihypertensives4,5,9 Interact
  Cardiovascular therapy4,9 Interact

Remedies: Wounds and many skin problems

Comfrey (Symphytum officinale) - Leaf or Root None reported4,5  

Remedies: Urinary tract infections

Cranberry (Vaccinium macrocarpon) - Berry Renally excreted drugs5 May increase elimination of some drugs excreted in the urine.

Remedies: Constipation, Indigestion, Water retention, Alcoholism

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: Indigestion, Heartburn and Arthritis

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: Breast cysts, Menopause and PMS symptoms

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: Boost immune system to prevent colds, flu, ear infections, sore throats, mouth ulcers (cankers), gingivitis and yeast infections

Echinacea (Echinacea species) - Root/Leaf Cancer treatements4 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: Colds, Herpes simplex, Sore throat, Flu, Inflammation

Elder (Sambucus nigra) - Berry None reported1,2,5,10  

Remedies: Arteriosclerosis, Diabetes, Eczema, Fibrocyctic breast disease, PMS, Rheumatoid arthritis

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: Lowering cholesterol and triglyceride levels, Diabetes, Arteriosclerosis

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: Migraines

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: Bone, Nail, Teeth, Skin health

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
e.g. Indomethacin4
Increases prevalence of stomach/intestinal ulcers

Remedies: Allergies, Asthma, Eczema, Irritable bowel syndrome, Menstrual cramps,
High blood pressure, Glaucoma

Forskohlii (Coleus forskohlii) - Root Clonidine23 Potential interaction

Remedies: Cardiovascular system, Congestive heart failure, Lowering cholesterol and triglyceride levels

Garlic (Allium sativum) - Bulb Anticoagulants2,4,5,7,9,19
e.g. Warfarin1,3,11,12,16,19,20
  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: Anti-nausea, Anti-vomiting, Blood circulation, Indigestion

Ginger (Zingiber officinate) - Root All drugs3 Increases absorption of drug
  Anticoagulants2,4,5,9,11,19,20 Inhibitory effect on thromboxane synthesis
  Cardiac therapy2,9
  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
  Sulfaguanidine3,4 Increases absorption of drug (rats)

Remedies: Alzheimer's disease, Blood circulatory diseases, Depression, Diabetes, Male impotence, Migraine, Multiple sclerosis, Tinnitus

Ginko (Ginko 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 
May introduce spontaneous bleeding
Potentiates effect of drug
May potentiate effects of drug
  Papaverine3 Potentiates effect of intracavernosal injection for impotence (in 20% of patients for whom previously ineffective)
Gingko may counter the sexual dysfunction that may be experienced with SSRIs
  Thiazide diuretic18 Herb decreases effect of drug, the interaction causes hypertension

Remedies: Flu, Common cold, Sore throat, Chronic fatigue syndrome, Fibromyalgia,
Alzheimer's disease, Arteriosclerosis,
Chemotherapy support, Male reproductive health, Stress, Diabetes

Ginseng North American (Panax quinquefolius) - Root Anticoagulation therapy3,4,12,16 
e.g. Warfarin20
Decreases INR levels
e.g. Diuretics20
Decreases diuretic action
Increases toxicity
  Estrogen Therapy4,9 Interact
  Oral Hypoglycemia therapy4,5
  Insulin3 Dose adjustment due to hypoglycemic effect
  MAOIs1, Interact
  Oral contraceptives12 Interact
  Psychotherapeutic medication4,12/Antipsychotics19 
e.g. Phenelzine4,9,16,20
  Steroids12,19 Interact

Remedies: Alzheimer's disease, Attention deficit disorder, Adjunctive chemotherapy,
Chronic fatigue syndrome, Common cold, Diabetes, Flu, Fibromyalgia, Stress

Ginseng Siberian (Eleuthero coccus senticosus) - Root Anticoagulants2,4 Interact
  Antipsychotics4,9 Interact (Stimulant activity)
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
  Digioxin2,5,16,19 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 dysentry and Proteus enterocolitis probably due to enhancement of t-lymphocyte activity

Remedies: Arthritis, Joint pain

Glucosamine Sulfate (2-Amino-2-deoxyglucose) Diabetic medication15 Causes a decrease in insulin secretion and in insulin sensitivity (in animal studies)

Remedies: Common cold, Chronic ear infections, Urinary tract infections, Crohn's disease

Goldenseal (Hydrastis canadensis) - Root Anticoagulants4,5,9 Potential interaction
e.g. Beta blockers5
Calcium channel blockers5
Increases effect of drug
e.g. Barbitu
Increases sleeping times (rats)
  Cardiovascular medications4
e.g. Digoxin5
Increases effect of drug
  CNS depressants5
e.g. Alcohol, benzodiazepines5
Enhances sedative effects
  Oral Hypoglycemia Therapy22 Herb lowers blood sugar levels

Remedies: Appetite stimulant, Digestion, Diuretic

Grapefruit (Citrus paradisi) - Fruit/Juice All Drugs including:
e.g. Midazolam, triazolam, alprazolam18, Buspirone18
Increases bioavailability
Inhibits metabolism by cytochrome P450-3A enzymes
  Calcium Antagonists3,18
e.g. Amiodipine, verapamil, nisoldipine, nifedipine, nitrenipine, felodipine, nimodipine, nicardipine
  Ethinyl estradiol3,18  
  HMG CoA reductase inhibitors18 
e.g. Atorvastatin, cerivastatin, lovastatin, simvastatin18

Remedies: Good nutritional value

Grape Seed Extract None reported5  

Remedies: Stimulates immune system, Infections, Gum disease, some cancer risk reduction,
Lowers cholesterol level, High blood pressure, High triglyceride levels

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: Angina, Arteriosclerosis, High blood pressure

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
Increases hypotension
  CNS depressants5 Addictive effects

Remedies: Anxiety, Insomnia

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: Varicose veins, Hemorrhoids, Blood circulation

Horse Chestnut (Aesculus hippocastanum) - Seed Anticoagulants3,5
Increased risk of bleeding

Remedies: Coughs, Diuretic, Sinus, Throat and lung problems

Horseradish (Armoracia rusticana) - Root Thyroid medications9 Interact

Remedies: Urinary tract infections, water retention

Juniper (Juniperus communis) - Berry Diuretic therapy2,9 Potentiates effect of drug
  Hypoglycemic therapy2,9 Potentiates effect of drug

Remedies: Anxiety

Kava (Piper methysticum) - Root Alcohol1,2,3,5,7,12,14 Potentiates action of herb
  Anticoagulants19 Interact
  Antidepressants7,12 Interact
  Antipsychotics7 Interact
e.g. Hexobarbital2
e.g. Pentobarbital3,5
Potentiates action of barbiturates
Potentiates effect of drug (animals)
Potentiates effect of drug
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
  Levadopa3 Decreases efficacy
  Hepato toxic drugs Potentiates effect of drug

Remedies: Herpes simplex, Indigestion, Insomnia, Nerve pain, Hyperthyroidism

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: Asthma, Bronchitis, Canker sores, Eczema, Herpes simplex, Indigestion, Heartburn,
Peptic ulcer, Chronic fatigue syndrome

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
Affect potassium levels
Iincreases toxicity due to decreases in potassium
  Cardiovascular drugs4 Interact
e.g. Stimulant laxatives3
Additive effect - increases potassium loss
e.g. Hydrocortisone2,3,16,
Potentiates effect of drug
Inhibit metabolism, increases plasma concentration
e.g. Loop diuretics2,11,
Potassium-sparing diuretics2,
Potassium-excreting agents or amiloride4, Spironolactone3,4,5,11,
Affects potassium, potentiates potassium depletion
  Hormonal therapy4,9
e.g. Oral contraceptives16
Hypertension, edema, hypokalemia
  Estrogen & antiestrogen2 Interact
  Insulin2,3,4,9 Increases electrolyte disturbances
  Nitrofurantoin2 Increases bioavailability

Remedies: Coughs, Colds, Asthma, Bronchitis, Flu, cardiovascular, Epilepsy

Lobelia (Lobelia inflata) - Aerial parts Nicotine therapy5 (smoking cessation treatments) Contra-indicated - Nicotine and Lobelin are chemically similar in structure

Remedies: Breathing problems, Asthma, Nasal congestion

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

Acetazolamide may cause increased concentration of ephedrine due to alkalinization of the urine
  ASA4 Potentiates effect of drug
  B adrenegic blockers4,5 Interact
  Cardiac glycosides1,4,11,13
e.g. Digitoxin7
Disturb heart rhythm
e.g. Dexamethasone3
Increases clearance and thereby reduces effect
  Centrally acting medications2,4
e.g. Antidepressants2
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
e.g. Tranylcypromine, selegiline, phenelzine, moclobamide3, 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: Peptic ulcer, Chron's disease, Diarrhea, Asthma, Common cold, Sore throat

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: Diarrhea, Stomach problems

Meadowsweet (Filipendula ulmaria) - Leaf/Flower All Drugs2,9

e.g. Anticoagulants2
Herb has similar interactions to those occurring with salicylates

Remedies: Gallstones, Psoriasis, Liver health

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: Blood pressure and heart, Mood, Migraine

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: BPH (enlarged prostate), hay fever

Nettle (Urtica dioica) - Leaf Anticoagulants4/
Coagulant therapy4
  Antihypertensives2,4,9 Interact
  CNS depressants4,9 Potentiates effect of drug
  Diabetic medication2,4,9 Interact
  Diclofenac (low dose)3,4 Leaf extract enhances anti-inflammatory effect of diclofenac
Potentiates effect of drug
  Diuretics2,5 Potentiates effect of drug
  Hypotension medication4,9 Interact
- Root Protatic Hyperplasia Therapy22
e.g. Tamsulosin
Potentiates effect of drug

Remedies: Anxiety, Insomnia

Passionflower (Passiflora incarnata) - Leaf Barbiturates4
e.g. Hexabarbital, Pentabarbital2,3
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: Infections and yeast infections

Pau D'arco (Tabebuia impetiginosa) - Bark Anticoagulants5,20 May potentiate effects of drug, prolongation of prothrombin time20
  Iron5 Decreases absorption of iron

Remedies: Migraine, Nerves, Stomach disorder, Heartburn, Herpes, Abdominal cramps

Peppermint (Mentha x piperita) - Leaf Ulcer treatment e.g. H2
Receptor Blockers
May antagonize achlohydria

Remedies: Chronic venous insufficiency

Pine Bark Extract (Pinus maritima) None reported4,5  

Remedies: Anemia, Skin healing, Respiratory problems, Immune system support, Digestion

- Resin
Tetracycline24 Increases effectiveness

Remedies: Constipation, Diarrhea, Hemorrhoids, Irritable bowel syndrome, Obesity, Arteriosclerosis, High cholesterol, High triglyceride level, Psoriasis

Psyllium (Plantago psyllium)
- Seed
All drugs1,3 May delay absorption of drugs
  Anti-coagulants21 Delays absorption of drug
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: Vitiligo (whitening of skin), Impotence, Female infertility, Urinary problems

Puncture Vine (Tribulus terrestris) None reported4  

Remedies: Urinary problems, Enlarged prostate

Pygeum (Prunus africana) - Bark Antibiotics for prostate and bladder infections4 Enhances effectiveness of drug

Remedies: Coughs, Eczema, Possible cancer reduction

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: Menstrual problems, Diarrhea, Canker sores

Red Raspberry (Rubus idaeus) - Leaf Antidiabetic agents5,9 Increases effectiveness of hypoglycemic action

Remedies: Lowering cholesterol levels

Red Yeast Rice lovastatin23
Additive effect similar in (Cholestin)

Remedies: Colds, Infection

Rosehips (Rosa canina) None reported5  

Remedies: Circulatory system, Heart problems, High blood pressure, Menstruation

Rosemary (Rosmarius officinalis) - Leaf Disulfiram5 Disulfiram reaction if herbal product contains alcohol

Remedies: Appetite stimulant, Chronic fatigue syndrome, Liver disease, Insomnia, Multiple sclerosis

Royal Jelly Antidiabetic agents5 May lead to loss of glycemic control in diabetic patients

Remedies: Menopause, Tonsillitis, Fever

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: BPH (enlarged prostate)

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: Coughs, Asthma, Urinary problems, Tonic

Schisandra (S. chinensis) - Berry Acetaminophen23 Reduces hepatotoxicity

Remedies: Infertility, Nerve disorders

Scullcap (Scutellaria laterifolia) - Aerial parts Centrally-acting medications2 Potentiates effect of drug
  Sedatives and tranquillizers3,4 Interact

Scullcap, Chinese (Scutellaria baicalensis) - Root Immunosuppressives5 Possible interaction
  Platelet aggregation inhibitors3,4 Potentiates effect of drug

Remedies: Constipation 

Senna (Cassia ssp) - 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: Depression, Vitiligo (whitening of skin), Recurrent ear infections

St. John's Wort (Hypericum perforatum) - Aerial parts All Drugs21,22 Drugs metabolized by cytochrome P450 3A4 enzyme system have potential to interact
  Antabase12 Interact
e.g. Trazadone
see MAOIs & SSRIs below
Serotonin syndrome
  Anti-epilepsy drugs17
e.g. Phenytoin
  Anti-retroviral drugs
e.g. Indinavir
  Atypical antipsychotics12
e.g. Olanzapine, risperidone12
  Beta2 agonists12 Interact
  Dextromethorphan2,12 Interact
  Dibenzazepine Derivatives2
e.g. Amitriptyline, doxepin, carbamazepine2
  Digoxin5,16,17 Interact
  Dopamine agonists12 Interact
e.g. Cyclosporine16,17,20
Interact - Decreases cyclosporine plasma concentration20
  Meperidine2 Interact
Enhances pressor effect
  Migraine therapies17 Interact
  Monoamine Oxidase Inhibitors (MAOIs)2,3,5,9,12,20
e.g. Phenelzine, tranylcypromine, isocarboxazid
e.g. Morphine2
  Oral Contraceptives16,17 Interact - can make ineffective
  Reserpine3 Decreases effect of drug (mice)
  Selective Serotinin Reuptake Inhibitors (SSRIs)2,3,4,5,7,12,16,17,20
e.g. Fluoxetine, paroxetine5, sertraline
Serotonin syndrome
e.g. Ephedrine, methyldopa, dopamine, trytophan
  Theophylline4,12,16,17,20 Interact
  Tyramine containing foods2,5 Decreases theophylline level
Interact (speculative)
  Warfarin17 Interact

Remedies: Yeast infection, Vaginitis, Athletes foot, Acne

Tea Tree Oil (Melaleuca alternifolia) - Leaf None reported2,4,5,12  

Remedies: Digestion, Fever, Headache, High cholesterol, Skin problems

Thyme (Thymus vulgaris) - Leaf & Flower None reported1,2,5  

Remedies: Respiratory problems, Mood, Tonic

Turkey Tail (Coriolus versicolor) Cyclophosamide23 Cyclophosamide23

Remedies: Bursitis, Rheumatoid arthritis, Liver health, Arteriosclerosis

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: Urinary tract infection

Uva Ursi see Bearberry    

Remedies: Insomnia

Valerian (Valeriana officinalis) - Root Alcohol5,11,16 Potentiates effects of alcohol
  Anticonvulsants12 Increases seizures
e.g. Pentobarbital, thiobarbital3
Increases sleeping time
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: High cholesterol, High triglyceride levels, Abdominal cramps, Menopause,
Muscle pain and spasms

Wild Yam (Dioscorea vilosa) - Root Oral Contraceptive22 Interact - may interfere with effectiveness of contraceptive

Remedies: Headache, Pain, Backache, Nerve pain, Toothache

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: Inflammation, Improves blood clotting, Diuretic, Fever, Some inflammatory disorders

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: Depression, Male impotence

Yohimbe (Pausinystalia yohimbe) - Bark a-adrenoceptor blocking agents3
e.g. Phenoxybenazamine, phentolamine3
Increases toxicity of yohimbine
  Amobarbital3 Interact
  Antidepressants5,7,20 Interact
  Atropine3 Interact
  Beta blockers3
e.g. Propranolol, penbutolol, metrprolol3
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
e.g. Chlorpromazine, promazine3
Increases toxicity of yohimbine
  Reserpine3 Interact
  Sedatives3 Increases effect of drug
  SSRIs5 Increases stimulation
e.g. Epinephrine, ephedrine, amphetamine, cocaine3
Increases toxicity of yohimbine
e.g. Chlorprotixene3
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


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