Herbs: Toxicities and Drug Interactions
Any conventional medication can have side effects. These side effects are
described and reported after drug trials and research studies have been
conducted. Side effects are further reported and evaluated after the
marketing of the medication. Information about drug components,
interactions, usage in pregnancy, nursing and childhood, and dosing limits
are outlined and made available in standard references for doctors treating
patients. Furthermore, the formulations of the drugs must satisfy strict
quality control standards to ensure conformity. These medications regularly
contain virtually uniform quantities and ratios of substances.
In contrast to conventional medications, unconventional treatments (such as
herbs) have little or no actual scientific basis so doctors can guide their
patients regarding proper usage or potential toxicity. There are no
standardized references and most of the herbal formulations have not been
analyzed, are not uniform, and have not been quality controlled. One batch
can be very different from the next.
Moreover, even if a given herb has a known toxicity, the manufacturer may
or may not warn consumers. Manufacturers are not required to alert
consumers to known dangers.
The point is that these "supplements" are not sanctioned, regulated, or
supervised by any agency.
The data are coming, although slowly. Dr. Lucinda Miller of Texas Tech
University Health Sciences recently reviewed known herb-drug interactions.
Her review was published for doctors in the medical journal Achives of
Internal Medicine 1998;158:2200- 2209. The list that follows is derived
from this article and includes summaries of various herbs with particular
focus on potential herb-drug interactions.
Keep in mind that the information in the "USES" section is for the most
part unsupported by verification of scientific studies. It should be noted
that simply because herbs are "natural" treatments, they are not
necessarily free from side effects.
USES: Chamomile is often used in the form of a tea as a sedative.
REACTIONS: Allergic reactions can occur, particularly in persons allergic
to ragweed. Reported reactions include abdominal cramps, tongue thickness,
tightness in the throat, swelling of the lips, throat and eyes, itching all
over the body, hives, and blockage of the breathing passages. Close
monitoring is recommended for patients who are taking medications to
prevent blood clotting (anticoagulants) such as warfarin/COUMADIN.
USES: Largely because white blood cells in the laboratory can be stimulated
to eat particles, echinacea has been touted to be able to boost the body's
ability to fight off infection.
REACTIONS: The most common side effect is an unpleasant taste. Echinacea
can cause liver toxicity. It should be avoided in combination with other
medications that can affect the liver (such as ketaconazole,
leflunomide/ARAVA, methotrexate/RHEUMATREX, isoniazide/INH/NIZORAL).
ST. JOHN'S WORT
USES: St. John's wort is popularly used as an herbal treatment for
depression, anxiety, and sleep disorders. It is technically known as
Hypericum perforatum. Chemically, it is composed of at least 10 different
substances that may produce its effects. The ratios of these different
substances varies from plant to plant (and manufacturer). Studies of its
effectiveness by the National Institutes of Health are in progress.
REACTIONS: The most common side effect has been sun sensitivity which
causes burning of the skin. It is recommended that fair- skinned persons be
particularly careful while in the sun. St. John's wort may also leave nerve
changes in sunburned areas. This herb should be avoided in combination with
other medications that can affect sun sensitivity (such as
tetracycline/ACHROMYCIN, sulfa- containing medications, piroxicam/FELDENE).
St. John's wort can also cause headaches, dizziness, sweating, and
agitation when used in combination with serotonin reuptake inhibitor
medications (such as fluoxetine/PROZAC and paroxetine/PAXIL).
USES: Garlic has been used to lower blood pressure and cholesterol (Dr.
Lucinda Miller notes that there is "…still insufficient evidence to
recommend its routine use in clinical practice.")
REACTIONS: Allergic reactions, skin inflammation, and stomach upset have
been reported. Bad breath is a notorious accompaniment. Studies in rats
have shown decreases in male rats’ ability to make sperm cells. Garlic may
decrease normal blood clotting and should be used with caution in patients
taking medications to prevent blood clotting (anticoagulants) such as
USES: Most commonly used for migraine headaches.
REACTIONS: Feverfew can cause allergic reactions, especially in persons who
are allergic to chamomile, ragweed, or yarrow. Nonsteroidal
antiinflammatory drugs (NSAIDs such as ibuprofen/ADVIL, MOTRIN or
naproxen/ALEVE) can reduce the effect of feverfew. A condition called
"postfeverfew syndrome" features symptoms including headaches, nervousness,
insomnia, stiffness, joint pain, tiredness, and nervousness. Feverfew can
impair the action of the normal blood clotting element (platelets). It
should be avoided in patients taking medications to prevent blood clotting
(anticoagulants) such as warfarin/COUMADIN.
USES: This herb is very popular as a treatment for dementia (a progressive
brain dysfunction) and to improve thinking.
REACTIONS: Mild stomach upset and headache have been reported. Ginko seems
to have blood thinning properties. Therefore, it is not recommended to be
taken with aspirin, nonsteroidal antiinflammatory drugs (such as
ibuprofen/ADVIL, MOTRIN or naproxen/ALEVE), or medications to prevent blood
clotting (anticoagulants) such as warfarin/COUMADIN. Ginko should be
avoided in patients with epilepsy taking seizure medicines, such as
phenytoin/DILANTIN, carbamazepine/TEGRETOL, and phenobarbital.
USES: Ginseng has been used to stimulate the adrenal gland, and thereby
increase energy. It also may have some beneficial effect on reducing blood
sugar in patients with diabetes mellitus. (Dr. Miller emphasized that there
is substantial variation in the chemical components of substances branded
REACTIONS: Ginseng can cause elevation in blood pressure, headache,
vomiting, insomnia, and nosebleeding. Ginseng can also cause falsely
abnormal blood tests for digoxin level in persons taking the drug for heart
disease. It is unclear whether ginseng may affect female hormones. Its use
in pregnancy is not recommended. Ginseng may affect the action of the
normal blood clotting element (platelets). It should be avoided in patients
taking aspirin, nonsteroidal antiinflammatory drugs (such as
ibuprofen/ADVIL, MOTRIN or naproxen/ALEVE), or medications to prevent blood
clotting (anticoagulants) such as warfarin/COUMADIN. Ginseng may also cause
headaches, tremors, nervousness, and sleeplessness. It should be avoided in
persons with manic disorder and psychosis.
USES: Ginger has been used as a treatment for nausea and bowel spasms.
REACTIONS: Ginger may lead to blood thinning. It is not recommended to be
taken with medications that prevent blood clotting (anticoagulants) such as
USES: Saw palmetto has been most commonly used for enlargement of the
prostate gland. (Dr. Miller emphasized that studies verifying this
assertion are necessary.) Saw palmetto has also been touted as a diuretic
and urinary antiseptic to prevent bladder infections.
REACTIONS: Saw palmetto can cause upset stomach. This herb may affect the
action of the sex hormone testosterone, thereby reducing sexual drive or
performance. Dr. Miller states that "While no drug-herb interactions have
been documented to date, it would be prudent to avoid concomitant use with
other hormonal therapies (eg, estrogen replacement therapy and oral
This listing represents only a small portion of herbal treatments.
Nevertheless, the popularity of herbal therapies is unquestionable. Doctors
routinely confront the unknown with their patients who are using herbs.
Doctors simply do not have any way of helping you to decide whether these
herbs are helpful or harmful for you, or whether they are interacting with
your current medications. There are no data.
For more health information please visit MedicineNet at www.medicinenet.com
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