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Counterfeit and Substandard Antimalarial Drugs

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.

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.

See also: Recent Warning About Counterfeit Artesunate (276 KB/2 pages)

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)

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.

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

1. Fake Artesunate in SE Asia. Newton P, Proux S, Green M, et al. (2001) The Lancet 357:1948-1950.
2. 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.
3. 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