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 (2).

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).

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.

Methods

Table I: Potential counterfeit products (i.e., test products).