Counterfeit drugs in the US drug supply are a serious public-health concern, but the scope of this problem is not known. A
counterfeit drug is legally defined as any brand-name or generic product sold under a product name without proper authorization
(1). By this definition, a counterfeit can be an actual product that has been relabeled or repackaged without authorization.
The counterfeit products that pose the most risk to patient health are those that contain incorrect ingredients, no active
ingredients, an improper dose, or harmful contaminants. Counterfeit drugs with no active ingredient or with the right active
ingredient at dosages other than the labeled dosage create nonpotent, subpotent, or superpotent medications. The risks involved
with taking a counterfeit drug include unexpected side effects, allergic reactions, and the worsening of the medical condition
Throughout the 1990s, the US Food and Drug Administration investigated an average of five counterfeit drug cases per year.
Since 2000, this number has sharply increased to more than 20 cases per year (3). In the United States, less than 1% of drugs
sold at drugstores are thought to be counterfeit. Current estimates of the prevalence of counterfeit medicines range from
5–10% internationally, and as high 50% in certain countries (2, 4).
Internet pharmacies have provided a convenient way for patients to fill their prescriptions and potentially save money. Internet
pharmacies also have created a new venue for the introduction of unapproved and counterfeit drugs into the US (5). The Government
Accountability Office (GAO), the investigative arm of Congress, examined Internet pharmacies and found that foreign Internet
pharmacies were shipping counterfeit versions of brand-name products such as Viagra (sildenafil citrate, Pfizer, New York)
and Oxycontin (oxycodone hydrochloride, Purdue Pharma, Stamford, CT) to the US. GAO also found that 45 of 68 Internet pharmacies
in the US, Canada, and other nations were selling prescription drugs over the counter. In addition, GAO discovered Internet
pharmacies that were filling orders for painkillers with less potent but potentially addictive medications (6).
In the US, FDA and the Customs and Border Protection collaborated to perform spot examinations of suspect mail shipments to
identify foreign drugs that were illegally imported. These examinations took place in July and August 2003 at postal facilities
in Miami, New York, San Francisco, and Carson, California. The drugs came from countries around the world, including Canada
(15.8%), India (14.3%), Thailand (13.8%), and the Philippines (8.0%) (7). Of the 1153 imported drugs examined, a total of
1019 (88%) were unapproved.
Such investigations indicate a greater prevalence of counterfeit drugs in markets other than the US, including in countries
where authentic pharmaceuticals are legally authorized for sale. Regulators need simple methods to identify potentially counterfeit
products. Simple visual inspection has obvious advantages and continues to function as the major initial screening technique.
Progress in process analytical technologies (PAT) that have been applied to pharmaceutical manufacturing may also play a role
in screening for counterfeit drugs. The authors' objective was to apply near-infrared (NIR) spectrometry to assess whether
eight suspected counterfeit drug products were authentic.
The eight suspected counterfeit products listed in Table I were purchased in Hong Kong in December 2007 (8). None of the
purchases required a prescription or involved a discussion with the pharmacist about medication needs. The seller of a purported
version of Cialis (tadalafil, Eli Lilly, Indianapolis, IN) in a 50-mg dosage form and of Viagra in a 100-mg dosage form bargained
substantially on the price, unlike the other pharmacies. Margins on medications are low in Hong Kong, and a willingness to
bargain may indicate that the product is not authentic. Labeling of each of these eight test products suggested that the product
was a brand product. Eli Lilly does not market Cialis in a 50-mg dosage form in the US.
Table I: Potential counterfeit products (i.e., test products).