Appendix 1
QUICK GUIDE TO HERB-DRUG
INTERACTIONS
The rapid increase in the use of herbal medicines has created a rapidly growing
database of known herb-drug interactions, many of which are presented in the table
below. Keep in mind, however, that our knowledge of the interactions among
pre-scription medicines, over-the-counter medicines, and herbal medicines continues to
change constantly.
To help detect possible herb-drug interactions, encourage patients to be open about
all medicines they may be taking, whether prescription, over the counter, or herbal. Ask
them to bring all of their medications with them to their next appointment. Caution
patients not to take herbal medicines in higher doses or more often than recommended.
Also, caution them not to experiment with herbal medicines. Urge them to tell all of their
health-care practitioners about all of the medicines they take.
ALOE GEL/JUICE Glyburide Increased hypo- Yongchaiyudha glycemic effect et al., 1996 ALOE LATEX Antiarrhythmics May potentiate the Blumenthal et al.,
Cardiac glycosides action of 1998 Corticosteroids cardiac
glyco-Licorice root sides and anti-Thiazide diuretics arrhythmic
agents (as do the other drugs listed)
ASTRAGALUS Acyclovir Increases effects DeSmet & ROOT Interleukin-2 D’Arcy, 1996
Azathioprine Caution use Cyclosporine
Methotrexate
BITTER MELON Chlorpropamide Increases hypo- Aslam & glycemic effect Stockley, 1979 BORAGE Anticonvulsants May lower seizure Miller, 1998
threshold
BROMELAIN Anticoagulants Increases Blumenthal et al., bleeding 1998
Tetracycline Increases plasma Neurauer, 1961 and urine drug
levels
Chloramphenicol Enhances drug Neurauer, 1961 Erythromycin levels
Novobiocin Penicillin
5-fluorouracil Can improve Taussig & Batkin, Vincristine efficacy 1998
BREWER’S YEAST MAO inhibitors Increased blood Blumenthal et al., pressure 1998
BUCKTHORN Cardiac glyco- May potentiate Blumenthal et al., BARK, BERRY sides toxicity with 2000
Quinidine long-term use
BUGLEWEED Thyroid Contraindicated Blumenthal et al., preparations 1998
SOURCE OF
HERB DRUG INTERACTION INFORMATION
BUPLEURUM Alcohol May increase WHO, 1999 CNS depressants sedation
Sedatives
CASCARA Cardiac glyco- May potentiate Blumenthal et al., SAGRADA BARK sides toxicity with 2000
Quinidine long-term use
CHASTE TREE Dopamine- May weaken Blumenthal et al., BERRY receptor antag- effect (animal 1998
onists (such as studies) haloperidol)
Metoclopramide Possible inter- Blumenthal et al., actions 2000
Hormone therapy Contraindicated Blumenthal et al., Oral contracep- 2000
tives
CAYENNE PEPPER Aspirin Reduced mucosal Yeoh et al., 1995 damage if
cayenne taken 30 minutes before aspirin
CINCHONA BARK Anticoagulants Increases effects Blumenthal et al., 1998
COLA NUT Caffeine Contraindicated Blumenthal et al., Psychoanaleptic 1998
drugs
DEVIL’S CLAW Antiarrhythmics Contraindicated ESCOP, 1999 ROOT
DONG QUAI Coumadin May increase Heck et al., 2000 effects of
medication
ECHINACEA Amiodarone If ⬎8 weeks, Miller, 1998
Anabolic steroids potential for Ketoconazole hepatotoxicity Methotrexate
Corticosteroids Antagonistic Cyclosporin effects
EPHEDRA Cardiac glyco- Cardiac arrhyth- Blumenthal et al., (MA HUANG) sides mias 1998
Halothane
MAO inhibitors May cause fatal Blumenthal et al., hypertension 1998
Ergotamine Hypertension WHO, 1999 Oxytocin
EUCALYPTUS OIL Drugs weakened Affects liver Blumenthal et al., (EXTERNAL OR or shortened detoxification 2000
INHALED)
EVENING Anticonvulsants May lower seizure Miller, 1998 PRIMROSE OIL threshold
FENNEL Ciprofloxacin Affects absorption, Zhu et al., 1999 distribution,
elimination
FENUGREEK Hypoglycemic May exaggerate Natural
Medi-agents effects cines,2000 Sulfonylureas
FEVERFEW Aspirin May increase Herbst, 1999 Coumadin bleeding time Miller, 1998 Nonsteroidal anti- Inhibits effects of Miller, 1998
inflammatory herb drugs
FLAXSEED Conventional May delay Blumenthal et al., medicines absorption 1998
Antidiabetic May slow glucose Blumenthal, medications absorption 2000 GARLIC Coumadin May increase Sunter, 1991
bleeding time Herbst, 1999 Miller, 1998 Ottariano, 1999 GINGER Anticoagulants May increase Lumb, 1994
bleeding time Herbst, 1999 Miller, 1998 GINKGO BILOBA Aspirin May increase Rosenblatt, 1997
Coumadin bleeding time Herbst, 1999 Miller, 1998 Papaverine May potentiate Sikora et al.,
effects of drug 1989 Trazodone May cause severe Prescriber’s
SOURCE OF
HERB DRUG INTERACTION INFORMATION
GREEN TEA Coumadin May increase Heck et al., 2000 effects
GURMAR LEAVES Glyburide May have additive Baskaran et al., Tolbutamide effects 1990 Insulin May reduce insu-
Shanmugasun-lin requirements daram et al., 1990 HAWTHORN LEAF Cardiac glyco- May enhance Blumenthal,
WITH FLOWER sides effects of drug 2000 Adenosine May increase Blumenthal, Caffeine coronary artery 2000 Epinephrine dilatation
Papaverine (controversial) Sodium nitrate
Theophylline
Digoxin May affect drug Miller, 1998 level monitoring
KARELA Biguanides May cause Miller, 1998 Insulin interactions
Sulphonylureas
KAVA KAVA Alcohol May potentiate Herbst, 1999 Barbiturates effects
Benzodiazepines
Levodopa May reduce effects Schelosky et al., 1995
LICORICE ROOT Spironolactone May increase loss WHO, 1999 of potassium Miller, 1998 Amiloride May increase loss WHO, 1999 Cardiac glyco- of potassium
sides
Thiazide diuretics
Digoxin May create prob- Miller, 1998 lems with drug
monitoring
MARSHMALLOW All May decrease Blumenthal et al., LEAF AND ROOT absorption of 1998
medications
OAK BARK All May decrease Blumenthal et al., absorption of 1998
PAPAYA Coumadin Increases effect of Shulman, 1997 medication
PANAX GINSENG MAO inhibitors May interact Blumenthal et al., Phenelzine 1998
Miller, 1998 Coumadin May alter bleeding Miller, 1998
times
Corticosteroids May have additive Miller, 1998 Estrogens effects
Digoxin May affect drug Miller, 1998 levels
Biguanides Should not admin- Miller, 1998 Insulin ister together
Sulfonylureas
PSYLLIUM Conventional May delay Blumenthal et al., medicines absorption 1998
Antidiabetic May slow glucose Blumenthal et al., drugs absorption 1998
RHUBARB ROOT Antiarrhythmics Increases toxic WHO, 1999 Cardiac glyco- effects
sides Corticoadrenal
steroids Thiazide diuretics
SARSAPARILLA Bismuth Increases Blumenthal et al., ROOT Digitalis glyco- absorption 1998
sides
Hypnotics Accelerates Blumenthal et al., elimination 1998
SAW PALMETTO Iron May limit Miller, 1998 absorption
SCOTCH BROOM MAO inhibitors May cause hyper- Blumenthal, tensive crisis 2000 SENNA Cardiac glyco- Long-term use can Blumenthal,
sides increase loss of 2000 Quinidine serum potassium
SIBERIAN Kanamycin May enhance Vereshchagin et GINSENG Monomycin effects of drugs al., 1998 STINGING Diclofenac Increased anti- Chrubasik et al.,
SOURCE OF
HERB DRUG INTERACTION INFORMATION
ST. JOHN’S WORT Selective serotonin Nausea, headache, Lantz et al., 1999 reuptake inhibitors tremors Roundtree, 2001 Anticonvulsants Contraindicated Roby et al., 2000 Antifungals because of Piscitelli et al., Antiretrovirals possible break- 2000 Calcium channel through bleeding,
blockers lowered blood Chemotherapeutics levels, de-Cyclosporine creased drug Macrolide anti- effectiveness
biotics Nonsedating
anti-histamines Oral
contracep-tives Warfarin
Tetracycline Increased risk of Herbst, 1999 blood clots
Iron May limit Miller, 1998 absorption
VALERIAN Alcohol May potentiate Upton, 1999 Barbiturates effects Herbst, 1999
McCaleb et al., 2000
Appendix 2
HERBS THAT MAY INCREASE
CLOTTING TIMES OR INTERACT WITH
ANTICOAGULANTS
Sources: Heck et al., 2000 and Ottariano, 1999.
Appendix 3
HERBS THAT MAY HAVE A
LAXATIVE EFFECT
•
Astragalus
•
Bilberry
•
Bromelain
•
Capsaicin
•
Dong quai
•
Evening primrose oil
•
Feverfew
•
Garlic
•
Ginger
•
Ginkgo biloba
•
Ginseng
•
Green tea
•
Horse chestnut
•
Red clover
•
Skullcap
•
Sheep sorrel
•
Willow bark
•
Aloe latex
•
Boneset
•
Buckthorn
•
Cascara sagrada
•
Dandelion root and leaf
•
Elder
•
Fennel
•
Milk thistle
•
Psyllium
Appendix 4
HERBS THAT SHOULD NOT BE TAKEN
INTERNALLY
LIVER TOXICITY:
•
Comfrey
•
Germander
•
Chaparral
•
Life root
CANCER-CAUSING EFFECTS:
•
Sassafras
LIFE-THREATENING TOXICITY IN ANIMALS:
•
Pennyroyal oil (has killed some animals after use as a flea repellent.)
Warning:Many plants are toxic and should never be used internally; consult a book on poisonous plants.
Appendix 5
HERBS THAT SHOULD NOT BE TAKEN
DURING PREGNANCY
•
Agave
•
Alder
•
Aloe (oral use)
•
Angelica
•
Buckthorn
•
Barberry
•
Basil
•
Bilberry leaves
•
Birthroot
•
Blue cohosh root
•
Black cohosh
•
Black walnut
•
Buchu
•
Cascara
•
Castor oil
•
Chaste tree berry
•
Coltsfoot
•
Cotton root bark
•
Damiana
•
Devil’s claw root
•
Dong quai
•
Ephedra
•
Ergot
•
False unicorn
•
Feverfew
•
Ginger
•
Ginkgo biloba (Egb)
•
Ginseng
•
Goldenseal
•
Gotu kola
•
Green tea (caffeine content)
•
Hawthorn
•
Hops
•
Horehound
•
Horse chestnut
•
Horseradish
•
Horsetail
•
Hyssop
•
Juniper berries
•
Kava kava
•
Licorice
•
Lobelia
•
Milk thistle
•
Mistletoe
•
Mugwort
•
Myrrh
•
Oregon grape
•
Osha
•
Pennyroyal leaf, flower,
and oil
•
Pleurisy root
•
Red clover
•
Rue leaf
•
Rhubarb
•
Sarsaparilla
•
Scotch broom
•
Senna
•
Shepherd’s purse
•
Southernwood
•
St. John’s wort
•
Tansy leaf
•
Uva ursi
•
Wormwood
•
Yarrow
•
Yellow dock
Appendix 6
HERBS THAT SHOULD NOT BE TAKEN
WHILE BREAST-FEEDING
Warning:Other herbs may be unsafe also. Tell patients to consult a health-care practitioner before taking any herb while breast-feeding.