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General Information
Counterfeit
(fake) drugs are products deliberately made to resemble a brand name
pharmaceutical. They may contain no active ingredients or contain ingredients
inconsistent with the package description. Counterfeiters tend to focus
on the more expensive brands.
Substandard
drugs are found even among cheaper products, because some manufacturers
wish to avoid costly quality control and good manufacturing practices.
The
quality of commercially available drugs varies greatly among countries.
Due to lack of regulations and poor quality control practices in some
countries, the amount of the active ingredient can be inconsistent. Poor
formulation techniques can affect the release of active ingredients from
a tablet, with some tablets releasing very little if any drug.
Some
drugs may be contaminated with other substances. Poor storage conditions,
especially in warm and humid tropical environments may contribute to chemical
degradation of many pharmaceuticals.
Counterfeiters may also acquire expired drugs and repackage them with
new expiration dates.
In
Cambodia in 1999, counterfeit antimalarial drugs were responsible for
the deaths of at least 30 people. A recent survey in Southeast Asia showed
that among 104 tablets presented as the antimalarial drug artesunate,
38% did not contain any artesunate (1).
Worldwide prevalence of counterfeit and substandard products are summarized
in a Drug Quality Report matrix by the U.S.
Pharmacopeia Drug Quality and Information (USP DQI) Program. Information on domestic (U.S.) issues regarding counterfeit and poor-quality drugs is provided by the U.S. Food and Drug Administration.
Users
of pharmaceutical products (not only antimalarials) should take the following
precautions:
- Travelers
should purchase in advance, in their home country, all the medicines
they will need.
- Travelers
should record the drug's generic and brand names as well as the name
of the manufacturer; should they run out, they can look for the correct
product.
- Make
sure that the drug is in its original packaging.
-
Inspect the packaging because many times poor quality printing indicates
a counterfeited product.
- Be
suspicious of tablets that have a peculiar odor, taste or color, or
that are extremely brittle.
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Two
blister packages of the antimalarial drug artesunate, one genuine
(right), one counterfeit (left). A well crafted hologram is the
only distinguishing feature of the genuine product.
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See
also: Recent
Warning About Counterfeit Artesunate, Illustrated. 5th edition, July 2006
(1.3
MB 10 pages. Courtesy: Wellcome Trust Oxford SE Asian Tropical Medicine
Research Units) Updated
July 2006
Field
Technique for Identifying Counterfeit Drugs
Sophisticated
analysis methods, such as high-pressure liquid chromatography (HPLC) and
spectrophotometry, are generally used in central laboratories to evaluate
drug quality.
In
areas where such facilities are not available, drug quality can be evaluated
in the field by two simple, effective, and low-cost techniques: thin-layer
chromatography (TLC) and colorimetry. The Minilab, developed by the German
Pharma Health Fund, uses these two techniques to assess the quality
of a wide range of essential drugs.
The
TLC technique consists of placing a spot of drug sample
on a thin layer of silica attached to a plate of glass, aluminum, or
plastic. The plate is then inserted into a vessel containing a solvent
mixture. By capillary action, the solvent mixture creeps up the silica
material and dissolves the sample. The drug sample consists of a mixture
of drug and inactive ingredients. These compounds will have various
affinities to the silica matrix and will migrate with the solvent at
various speeds. This characteristic effectively separates out a mixture
of compounds. After migration of the solvent is complete, individual
components can be visualized by chemical treatment or ultraviolet (UV)
absorbance. The distance that the components migrate is characteristic
for each compound; therefore the active ingredient can be recognized
by comparison with a known drug standard. The solvent can be modified
to increase resolution between various components. This method is relatively
inexpensive, specific, and sensitive. It is commonly used to assess
drug quality.
Related Source: Compendium
of Unofficial Methods for Rapid Screening of Pharmaceuticals by Thin-Layer
Chromatography (On
Pharmweb.net site)
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Colorimetric
test for artesunate. From left to right: chloroquine, counterfeit
artesunate, genuine artesunate, sulfadoxine-pyrimethamine. The genuine
artesunate is distinguished by a positive yellow appearance.
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Colorimetry
uses chemical reactions or characteristic acidity (pH) properties to
evaluate drug quality. This method is convenient because it is very
rapid and highly specific. The intensity of a positive color reaction
is usually proportional to drug concentration, so visual assessment
can easily be made for semi-quantitative purposes by comparison with
standards of known concentration. Color intensity can be measured
using a portable filter photometer to give a quantitative assessment.
A colorimetric test developed at CDC was used to assess the quality
of artesunate in Southeast Asia (1). This test requires only a small
portion of tablet scrapings (1%), allowing the tablet to still be
available for treatment. After exposure of the material to a strong
base and subsequent treatment with the reagent, a distinct yellow
color is produced if artesunate is present (2). See Colorimetric
test for artesunate.
A
similar test has also been developed for artemether (3).
References
- Fake Artesunate in SE Asia. Newton P, Proux S, Green M, et al. (2001)
The Lancet 357:1948-1950.
- A Colorimetric Field Method to Assess the Authenticity of Drugs Sold
as Antimalarial Artesunate. Green MD, Mount DL, Wirtz RA, White
NJ. (2000) Journal
of Pharmaceutical and Biomedical Analysis 24:65-70.
- Authentication of Artemether, Artesunate, and Dihydroartemisinin
Antimalarial Tablets Using a Simple Colorimetric Method. Green MD,
Mount DL, Wirtz RE. (2001) Tropical Medicine and International Health
6(12):980-982
Page last modified : July 26, 2006
Content source: Division of Parasitic Diseases
National Center for Zoonotic, Vector-Borne, and Enteric Diseases (ZVED)
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