Journal of HerbMed Pharmacology
Journal homepage: http://www.herbmedpharmacol.com
J HerbMed Pharmacol. 2013; 2(2): 21-22.
Toxicity and safety of medicinal plants
*Corresponding author: Medical Plants Research Center, Shahrekord
University of Medical Sciences, Shahrekord, Iran.
Hamid Nasri1, Hedayatollah Shirzad2*
1Department of Nephrology, Division of Nephropathology, Isfahan University of Medical Sciences, Isfahan, Iran
2Medical Plants Research Center, Shahrekord University of Medical Sciences, Shahrekord, Iran
Implication for health policy/practice/research/medical education:
Although medicinal plants are widely used and assumed to be safe, however, they can potentially be
toxic especially in pregnancy. Where poisoning from medicinal plants has been reported, it usually
has been due to misidentication of the plants in the form in which they are sold, or incorrectly
preparation and administration by inadequately trained personnel. erefore, preferably should be
administered by trained personnel.
Please cite this paper as: Nasri H, Shirzad H. Toxicity and safety of medicinal plants. J HerbMed
Plarmacol. 2013; 2(2): 21-22.
A B S T R A C TA R T I C L E I N F O
Received: 17 August 2013
Accepted: 14 November 2013
ePublished: 1 December 2013
It has been considered that if a drug is eective, it will
have side eects. erefore, herbal medicines as drugs
either have side eects or are ineective. However, herbal
medicines are generally considered to be safe and eective
agents. erefore, people every year turn to herbal medicine
because they believe plant remedies are free from undesirable
side eects (1).
Approximately 8% of all hospital admissions in the United
State are due to adverse reactions to synthetic drugs. At least
100,000 people a year die from these toxicities. It means at
least three times as many people are killed in the U.S. by
pharmaceutical drugs as are killed by drunken drivers.
ousands die each year from supposedly “safe” over-the-
counter remedies. Deaths or hospitalizations due to herbs are
so rare that they are hard to nd. e United State National
Poison Control Centers does not even have a category in their
database for adverse reactions to herbs. However, toxicity of
herbal medicines needs to be seen in context (2).
ere are a few plants that are “drug like” and their action
approaches that of pharmaceuticals. e number of these
plants is relatively few. Digitalis is one of these classic examples.
Herbalists use these plants in allopathic treatment strategies
and in some countries such as Britain their vast availability is
restricted by law (3).
e majority of medicinal plants contain dozens of dierent
compounds, some of them with great complexity. Plants
substances such as mucilages, polysaccharides and tannins
modulate and modify the eects of any “active principles”.
Studies have shown that the extract eects of whole plants
cannot be mimicked by administering isolated and puried
constituents of the herbs. Biological sciences believe that
the whole plant being greater than the sum of the parts
which reects the inherent conservatism of the medical
Pharmaceutical drugs are designed to elicit specic reactions
and their “side eects” are usually traded as a “risk” against the
“benet” of the primary eect. Medicinal plants tend to have
several broad actions on physiological systems at the same
time. ese actions are usually complementary or synergistic
and oriented in the same general therapeutic direction, and
oen non-specic, and rarely adverse. Medicinal plants
actions are too complex and oen cannot be adequately
described using the vocabulary of “medication” action terms
such as diuretic (3).
A drug addresses symptoms caused by specic disease as
understood by scientic pathology. However, medicinal plants
are usually directed towards aiding the body’s own healing
processes. Medicinal plants act gently; usually attempting
to help remove excesses that have become preponderant
or “support” the systems and processes that have become
decient Symptom relief is only a section of herbal therapeutic
strategies. For example, serum arthritic is conventionally
treated with steroid anti-inammatory drugs which have
widespread disturbing side eects. e plant approach to these
conditions causes facilitation of elimination via kidneys and
hepatic/ biliary routes; dietary modication of metabolism,
moistening of dry synovia, stimulation of circulation in the
aected regions, etc (1).
Nasri H et al.
2Journal of HerbMed Pharmacology, Volume 2, Number 2, December 2013 http://www.herbmedpharmacol.com
Herbal therapy is a wholistic therapy, integrating emotional,
mental and spiritual levels. Life style, emotional, mental
and spiritual considerations are part of any naturopathic
approach. e use of herbs does not generally involve “drug”
actions or adverse eects. Of course, informed knowledge of
the eects of medicinal plants as well as doing a clinical trial to
understand the appropriate medical application is necessary.
It has been suggested that we use the terms indications and
contraindications for using a herb instead of “side eects” (3).
Many people seeking herbal medical treatment are already
involved in pharmaceutical therapies. Herbal medicines
may act as agonists or potentiate some drug therapies,
and an understanding of conventional drugs is an essential
prerequisite for eective herbal therapeutics. In many
cases, herbalists do not like to treat the primary presenting
symptom undergoing drug treatment but rather concentrate
on supporting other systems and functions stressed by the
primary symptom. is allows the body to recover its strength
and healing potential so it can then direct these capabilities
toward repairing the presenting condition (1).
Many ordinary foods contain substances that can be regarded
as potentially poisonous, such as the cyanogenic glycosides in
many fruit seeds, alpha gliadin produced by gluten in wheat
oats and rye, the thiocyanates of the brassica vegetables,
lectins of many pulses including soya and red kidney beans
and alkaloids of the Solanaceae. Nonetheless these foods are
generally regarded as safe. Similarly, both water and oxygen
can kill in excessive amounts, so quantity is oen an important
In practice, three groups of herbs can be identied from a
safety point of view. Firstly there are some herbs that contain
near pharmaceutical concentrations of poisonous constituents
which should not be taken internally by unqualied persons.
Examples are Arnica spp, Atropa belladonna, Aconitum spp
and Digitalis spp. Secondly, are the herbs with powerful
actions. ese herbs are safe under appropriate conditions.
Finally, there is an idiosyncratic grouping of herbs which
have been alleged to exhibit specic kinds of toxicity. e
best known is the hepatotoxicity of pyrrolizidine-alkaloid-
containing plants such as Comfrey. Other examples are
Dryopteris, Viscum, and Corynanthe (2).
Pregnancy is particular condition which should be considered
as a time of minimal medical intervention, and in particular
regard pregnancy should be considered as a “contraindication”
to taking herbal medicines. e evidence of teratogenicity in
humans arising from herbal remedies is rare, but since such
evidence would be hard to come by, it is better to be avoided
during pregnancy (4).
Herbalists justiably point out that scientic studies with
isolated compounds, on non-human or even non mammalian
organisms, or in vitro, with doses tens or hundreds of times
the equivalent medicinal dose, have no arguable extrapolation
to the clinical situation using whole herb at appropriate
medicinal doses (4).
Lack of herbal knowledge by some scientic investigators leads
to misleading results - one of the commonest mistakes being
the failure to verify the actual identity of plant material used
in their experiments, let alone the detection of contaminants!
ese points beg the question of what paradigm can be used
for research into the safety and ecacy of herbal therapies.
e double blind placebo controlled clinical trial is open to a
range of criticisms from the paradigm employed by herbalists
is another story (4).
In sum the vast majority of medical herbs are safe for
consumption; however, it would be prudent to follow simple
but sensible guidelines in self-treatment:
1. Only herbs recommended in respected herb books
should be used.
2. New or unproven remedies should be avoided.
3. It is better to discontinue the herb consumption if no
benet or result was obtained aer a moderate period of
time, or if adverse reactions toke place.
4. Patients or physicians should not engage in drug usage
for complex conditions without knowledge.
5. Drug interactions and contraindications must be
considered on an individual basis.
6. It is better to avoid herbal remedies during pregnancy.
In overall although medicinal plants are widely used and
assumed to be safe, however, they can potentially be toxic.
Where poisoning from medicinal plants has been reported, it
usually has been due to misidentication of the plants in the
form in which they are sold, or incorrectly preparation and
administration by inadequately trained personnel.
HN and HS wrote the manuscript equally
Conict of interests
e authors declared no competing interests.
Ethical issues (including plagiarism, data fabrication, double
publication) have been completely observed by the author.
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