Manual of Clinical Nutrition

Herb and Drug Interactions

Manual of Clinical Nutrition Management II- 35 Copyright © 2013 Compass Group, Inc.

Herb

Classifications

Common

Indications

Possible Side

Effects

Herb-

Medication

Interactions

Patient Guidelines

Garlic
Allium sativum

*Antiatherosclerosis

(lipid-lowering anti-

thrombotic,

fibrinolytic,

antihypertensive) (1-2)

Contraindications:

Lactation; prolongs

bleeding time, and

should be discontinued

1 - 2 weeks prior

surgery (3)

Stomach upset,

headache, myalgia,

fatigue, and vertigo

(2)

Sulfuric odor, contact

irritation, and

dermatitis (2)

May increase the

effect of

antihypertensive

medications and

anticoagulant

medications, such

as aspirin, NSAIDs,

or warfarin (2,5)

Recommended daily dosage:

a commercial preparation of

600 to 900 mg (containing 3

mg of allicin or a total allicin

potential of 5,000 μg) in an

enteric-coated form QD (2)

or one clove of raw garlic

(equal to 4 g) QD or BID (2).

Ginger
Zingiber officinale

*Loss of appetite,

nausea, travel sickness,

and dyspeptic

complaints (1,2)

Contraindications:

Germany’s Commission

E contraindicates the

use of ginger for

morning sickness

associated with

pregnancy (2); gallstone

conditions; and

persons at risk for

hemorrhage (2).

Heartburn (1)

Doses >6 g/day may

lead to ulcer

formation (2).

Allergic reaction

(rare) (1)

May exacerbate

the anticoagulant

effects of warfarin

(2,3)

May decrease

effectiveness of

antacids, H2

blockers, and

proton pump

inhibitors

May interfere with

diabetic and blood

pressure

medicines (3)

Use only briefly during

pregnancy.

May prolong bleeding, so do

not use after surgery.

Patients receiving

anticoagulant medications

or patients with a history of

gallstones should not take

ginger (2,3,4).

Usual dose for antiemetic is

1 to 2 g freshly ground

ginger taken with liquid and

in two divided doses (2)

Ginkgo
Ginkgo biloba

*Symptomatic relief of

organic brain

dysfunction and

intermittent

claudication (dementia,

peripheral occlusive

arterial disease

[POAD]) (1,2); improves

memory

*Vertigo (vascular

origin) (2)

*Tinnitus (vascular

origin) (2)

Gastrointestinal tract

disturbance,

headache, and

(rarely) contact

dermatitis (1-3); blood

pressure

irregularities (2);

blood glucose level

changes (3)

Patients with known

risk factors for

intracranial

hemorrhage (eg,

systemic arterial

hypertension,

diabetes amyloid

senile plaques)

should avoid use of

ginkgo (2).

May exacerbate

the effects of

antithrombolytic

agents (eg,

anticoagulants,

antiplatelets,

aspirin, or

acetaminophen) as

a result of a potent

inhibitory effect on

platelet-activating

factor (2,4)

May cause

hypomania if taken

with fluoxetine

May interact with

medicines that

lower seizure

threshold and

thiazide diuretics

(3)

Ginkgo is available in a

capsule, tablet, or liquid

form. Absorption is

unaffected by food intake (1).

Recommended daily dosage

for cerebrovascular

insufficiency (eg, dementia,

POAD, and equilibrium

disorders) is

120 to 240 mg of

standardized dried extract

in 2 or 3 oral doses (2,6). A 6-

to 8-week course is advised

to determine effectiveness

of therapy.

Avoid taking with Tegretol,

Equetro, Carbatrol

(cabamazepine), and

Depakote (valproic acid) (7)