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Herb-Drug Interactions
“Concurrent use of herbs may
mimic, magnify, or oppose the
effect of drugs”
Numbers of Herb-Drug Interactions
Reported by Various Sources
Source
Botanical Safety Handbook
# of herbs
# of herbs
described w/interactions
540
207
11
79*
84
60
17
15
The Complete German
Commission E Monographs
308
35
Herbal Medicines-A Guide for
Health-Care Professionals
107
42
28
14
Herbal Medicines-A Guide for
Health-Care Professionals
141
---†
Mechanisms of Drug
Interactions
NA
55‡
HealthNotes Clinical
Essentials
151
48
Herb Contraindications and
Drug Interactions
British Herbal Compendium
ESCOP Monographs on the
Medicinal Use of Plant Drugs
WHO Monographs on
Selected Medicinal Plants
Types of Herb-Drug Interactions
Type of Interaction
Modifies intestinal absorption of medicines
Impairment by hydrocolloidal fiber
Selective precipitation of drug by tannins
Selective precipitation of drug by iodine
Enhancement of drug by pungent herbs
Potentiates cardiotonic medicines
Herbal cardiotonics
Stimulant laxatives
Enhancers of urinary potassium excretion
Potentiates sedative or tranquilizing
medications
# of Herbs
23
38
12
4
11
17
8
21
Modifies blood sugar in insulin-dependent diabetes
Hypoglycemic herbs
72
Hyperglycemic herbs
9
Modifies effects of prothrombopenic anticoagulants
Potentiation by coumarin-containing plants
7
Potentiation by platelet aggregation inhibitors 11
Antagonism by plants high in vitamin K
18
Incompatible w/medications for gastrointestinal tract
Stimulants for secretion of stomach acid
37
Potential Severity of HerbDrug Interactions
Severity of
Interaction
# (and %) of
Interactions
Beneficial effects or
reduction of drug side
effects
Innocuous effects
18
(17.0)
28
(26.4)
Production of disease
or enhancement of
side effects
18
(17.0)
Threat to life through
interaction with
dangerous drugs
Total
42
(39.6)
106
(100 %)
Potentially Serious Herb-Drug
Interactions
Type of Interaction
# of Herbs
Affects absorption of drugs
17
Enhances potassium loss if
given with diuretics
5
Interacts with monoamine
oxidase inhibitors
11
Interacts with cardiac
glycosides
12
Enhances effects of
barbiturates
10
Alters effects of blood sugar
medications
9
Interacts with anticoagulant
medications
9
Herb-Drug Interactions
“Evidence that it Occurs”
(2,000 Study)
No. and % of
interactions
Type of study
Animal trials
Speculative
Empirical
Human case reports
Human clinical trials
Human studies
TOTAL
28
27
26
15
11
36
143
19.5
18.9
18.2
10.5
25.2
7.7
Herb-Drug Interactions
(Some Examples)
• Bleeding when warfarin is combined with ginkgo or
garlic
• Mild serotonin syndrome when S.J.W. is taken with
serotonin re-uptake inhibitors
• Decreased bioavailability digoxin and cyclosporin
when S.J.W. is consumed
• Induction of mania in depressed patients with
neoleptic drugs; are taken with betel nut (Areca sp.)
• Increased risk of hypertension when tricyclic
antidepressants are combined with yohimbine
• High soluble fiber plants such as psyllium decreases
drug absorptions
Herb-Drug Interactions
“10 herbs you can trust”
•
Bilberry (Vaccinium sp.) for night blindness, simple diarrhea,
glaucoma and cataracts
•
Echinaceae for colds, flu and respiratory infections
•
Feverfew (Tonacetum sp.) to prevent migraines
•
Ginger (Zingiber sp.) for motion sickness, indigestion
•
Ginkgo to improve memory – avoid with blood thinners
•
Hawthorne (Cratagus sp.) reduce high blood pressure, treat
congestive heart failure
•
Milk Thistle (Silybum sp.) to treat liver disease
•
Saw palmetto (Serenae) to increase urine flow
•
Saint John’s Wort (Hypercium sp.) for mild depression
•
Valerian (Valeriana sp.) for insomnia and restlessness
* American Botanical Council and based on the German Commission
E. monographs.
Herb-Drug Interactions
“The Dirty Dozen”
Category 1: “Definitely hazardous”
a.
Aristolochic acid (Aristolochia sp.)
1993: 30 cases of kidney failure among Belgian
women using powered Chinese herbs (weight control)
which was adulturated with Aristolochia sp.
2002: 237 of nephropathy is Asia and Europe after
prolonged use of Chinese herbs for increased athletic
performance. Product was contaminated with
aristolochic acid.
(aristolochic acid is metabolically activated to
carcinogen compounds by cytochrome P450)
b.
Germander (Teucrium sp.)
1990’s in France: 26 cases of hepatic toxicity after 9
weeks use of germander for weight and cholesterol
reduction.
- jaundice disappears within 8 weeks discontinued use
but returned “promptly” after re-use started
- the furano diterpenoids in germander causes
reduction in glutathione (reversed with cystine)
* Alternative Medicine Alert Vol. 7: 2004 and Consumer
Reports May 4, 2004
Herb-Drug Interactions
“The Dirty Dozen”
Category 2: “Potentially hazardous with prolonged internal use
a.
Comfrey (Symphytum sp.) – contains pyrrolizidine alkaloids
which are hepatotoxins. Concentration is 100x higher in
roots than aerial parts.
Primary use: as a tea, but has been used long-term (safely)
in the form of powdered root for external treatment of insect
bites, sprains, inflammations and bruises.
b.
Chaparrel (Larrea sp.) – long-term use as a external antiinflammatory but if used internally can cause non-fatal
kidney/liver damage. Since 1969, when it was reported to
cause remission of melanoma, the use of chaparrel in tea
has been widespread yet few adverse case reports except
where other herbs have been used.
c.
Kava (Piper sp.) – popular use as a relaxant but in 2002
FDA issued a warning about its association with liver
toxicity. In 2003, Kava was banned in Germany. It’s toxicity
has not been established so care in its use should be
standard procedure.
d.
Androstenedione – a non-herb supplement derived from
animal adrenal glands and gonads. It is used in conjunction
with some herbs as a testosterone precursor to enhance
muscle development. Currently banned by most amateur /
athletic organizations. Short-term use has little or no side
effects but evidence of increased cancer rates with longterm usage.
Herb-Drug Interactions
“The Dirty Dozen”
Category 3: Hazardous with acute excessive dosage”
a.
Pennyroyal oil (Hedeoma sp.) excessive use of the volatile
oil to treat colds should be avoided such at high level as it is
a hepatoxic/nephrotoxic compound. In the 1980’s reports
of women taking toxic levels of pennyroyal oil to induce
abortion but not effective.
b.
Yohimbine (Pausinystalia sp.) has been marketed for 80
years to treat impotence. Potential toxicity: hypertension,
anxiety, dizziness but rarely death.
c.
Lobelia (Lobelia sp.) widely used in American herbalism as
a expectorant. Potential toxicity: nausea, vomiting,
arrhythmias and rarely death; often used with other herbals
as a muscle relaxant (external) or internally to treat
respiratory problems.
d.
Bitter orange (Citrus sp.) – the Seville orange popular in
some areas of South America for insomnia, anxiety and
epilepsy. Also, becoming popular as a anti-obesity agent.
Since the amines present apparently increase lipolysis and
fat oxidation in mammalian fat cells. Concern is with
occurrence of arrithymias in obese people use bitter orange
formulations