Contamination of Herbal Drugs and Herb–Drug Interactions
Conventional synthetic pharmaceuticals such as synthetic corticosteroids, nonster-
oidal anti-inflammatory drugs and other prescription drugs, potent drugs such as
2.6 Contamination of Herbal Drugs and Herb–Drug Interactions 41
phenylbutazone, in fact examples of almost every therapeutic drug class have been
found in certain herbal remedies as contaminants. A recent study by Ramsay et al.
found that potent corticosteroids had been deliberately added to herbal creams in
order increase their efficacy [89]. This problem is widespread, and occurs in both
Oriental and European countries [90–94]. These “adulterated” herbal medicines
sometimes result in serious ailments such as acute renal failure [10, 95–99].
Many people, especially those living with HIV/AIDS, use both herbal medicines
and prescription drugs. A number of clinically significant interactions between
prescribed and herbal medicines have been identified. When these medications
are used together, they can interact in the body, causing changes in the way the
herbs and/or the drug works. Such changes are called herb–drug interactions.
Concurrent use of herbal or homeopathic remedies alongside prescribed or over-
the-counter medicines are frequent, and may mimic, magnify, or oppose the effect
of the drug [100].
Herb–drug interactions are not chemical interactions between a drug and a her-
bal component to produce something toxic. Instead, the interactions generally
cause either an increase or decrease in the amount of drug in the bloodstream. As
with conventional medicines, herbal medicines interact with drugs in two general
ways: pharmacokinetically and pharmacodynamically. Pharmacokinetic interac-
tions result in alterations in the absorption, distribution, metabolism, or elimina-
tion of the drug or natural medicine. These interactions affect drug action by quan-
titative alterations, either increasing or decreasing the amount of drug available to
have an effect. Pharmacodynamic interactions cause alterations in the way a drug or
natural medicine affects a tissue or organ system. These actions affect drug action
in a qualitative way, either through enhancing or antagonizing effects.
Herb–drug interactions change the effectiveness of the treatment, sometimes
resulting in potentially dangerous side effects, possibly leading to toxicity, and/or
reduced benefits. They can modify the mode of action of the drug, leading to unex-
pected complications or enhancement of the therapeutic effect, possibly leading to
overmedication and an impact on health. Drug interactions are a significant prob-
lem in association with the use of St John’s wort [101, 102].
The risk of herb–drug interactions is not limited to synthetic drugs. Herbal sup-
plements and certain foods can interact with medications. Unfortunately very little
is known about these interactions and there is little available scientific research on
herb–drug interactions. When combining herbal therapies with other medica-
tions, it is important to watch for potential symptoms and to inform health care
providers. It is essential to train doctors to appreciate that drug interactions exist
and to emphasize the importance of the need for physicians and naturopathic doc-
tors to work together.
Currently, there is very little information published on herb–drug interactions
[103–109]. Controlled clinical studies are needed to clarify and determine their clin-
ical importance and more research is required to define them.
42 2 Quality Control, Screening, Toxicity, and Regulation of Herbal Drugs
Conventional synthetic pharmaceuticals such as synthetic corticosteroids, nonster-
oidal anti-inflammatory drugs and other prescription drugs, potent drugs such as
2.6 Contamination of Herbal Drugs and Herb–Drug Interactions 41
phenylbutazone, in fact examples of almost every therapeutic drug class have been
found in certain herbal remedies as contaminants. A recent study by Ramsay et al.
found that potent corticosteroids had been deliberately added to herbal creams in
order increase their efficacy [89]. This problem is widespread, and occurs in both
Oriental and European countries [90–94]. These “adulterated” herbal medicines
sometimes result in serious ailments such as acute renal failure [10, 95–99].
Many people, especially those living with HIV/AIDS, use both herbal medicines
and prescription drugs. A number of clinically significant interactions between
prescribed and herbal medicines have been identified. When these medications
are used together, they can interact in the body, causing changes in the way the
herbs and/or the drug works. Such changes are called herb–drug interactions.
Concurrent use of herbal or homeopathic remedies alongside prescribed or over-
the-counter medicines are frequent, and may mimic, magnify, or oppose the effect
of the drug [100].
Herb–drug interactions are not chemical interactions between a drug and a her-
bal component to produce something toxic. Instead, the interactions generally
cause either an increase or decrease in the amount of drug in the bloodstream. As
with conventional medicines, herbal medicines interact with drugs in two general
ways: pharmacokinetically and pharmacodynamically. Pharmacokinetic interac-
tions result in alterations in the absorption, distribution, metabolism, or elimina-
tion of the drug or natural medicine. These interactions affect drug action by quan-
titative alterations, either increasing or decreasing the amount of drug available to
have an effect. Pharmacodynamic interactions cause alterations in the way a drug or
natural medicine affects a tissue or organ system. These actions affect drug action
in a qualitative way, either through enhancing or antagonizing effects.
Herb–drug interactions change the effectiveness of the treatment, sometimes
resulting in potentially dangerous side effects, possibly leading to toxicity, and/or
reduced benefits. They can modify the mode of action of the drug, leading to unex-
pected complications or enhancement of the therapeutic effect, possibly leading to
overmedication and an impact on health. Drug interactions are a significant prob-
lem in association with the use of St John’s wort [101, 102].
The risk of herb–drug interactions is not limited to synthetic drugs. Herbal sup-
plements and certain foods can interact with medications. Unfortunately very little
is known about these interactions and there is little available scientific research on
herb–drug interactions. When combining herbal therapies with other medica-
tions, it is important to watch for potential symptoms and to inform health care
providers. It is essential to train doctors to appreciate that drug interactions exist
and to emphasize the importance of the need for physicians and naturopathic doc-
tors to work together.
Currently, there is very little information published on herb–drug interactions
[103–109]. Controlled clinical studies are needed to clarify and determine their clin-
ical importance and more research is required to define them.
42 2 Quality Control, Screening, Toxicity, and Regulation of Herbal Drugs
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