Herbs: Toxicities and Drug Interactions
Medical Author: William C. Shiel, MD, FACP, FACR
Medical Editor: Frederick Hecht, MD, FAAP, FACMG
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.
Data is coming, although slowly. Dr. Lucinda Miller of Texas
Tech University Health Sciences reviewed known herb-drug
interactions. Her review was published for doctors in the medical
journal Archives of Internal Medicine. 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.
Chamomile
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).
Echinacea
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 (Nizoral, Extina,
Xolegel, Kuric), leflunomide
(Arava), methotrexate (Rheumatrex),
isoniazid (INH, Nydrazid,
Laniazid)].
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).
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