Introduction
The increased counterfeiting of pharmaceutical products in recent years has grown into a global healthcare crisis affecting patients the world over. The effects of pharmaceutical counterfeiting on this scale are numerous. First and foremost is the impact to the patients themselves. In addition to not receiving the therapeutic benefit of the authentic drug product, the patient taking a counterfeit medicine also risks coming into contact with materials which may be hazardous or toxic. Materials such as cement, gypsum, industrial solvents and lead based road paints have been identified in counterfeit pharmaceuticals1. Additionally counterfeit pharmaceuticals, specifically those containing authentic active ingredient(s) but at either inefficacious levels or in undesirable chemical forms, may lead to decreased levels of bio-availability and the development of resistant strains of a disease2. In other cases, unrelated pharmaceutical products have been altered or repackaged so they can be passed off as a more profitable product. Common over the counter pain relievers such as aspirin have been used in this way3.
An additional, more subtle aspect of pharmaceutical counterfeiting involves the use of stolen authentic product, often referred to as illegal diversion. Illegal diversion can occur at any stage within the drug supply chain, from the manufacturer to the individual retailer, and may involve product which is past its expiry date and slated for disposal. Illegal diversion represents a unique challenge for the analytical laboratory since testing of the product will indicate that the sample in question is authentic, appearing physically and chemically identical to the legitimate product.
Strategy and Decision Making
In building a laboratory strategy for the interrogation of suspected pharmaceutical counterfeits, it is important to understand our customer’s questions. All aspects of the analytical portion of the investigation will be based on the type and nature of information sought. Everything from the basic experimental design to the actual selection of analytical techniques to be employed will be based on a clear understanding of what we are being asked to prove.
This understanding is necessary to focus the analytical needs of the investigation and to avoid wasted time and effort. Without this focus we may engage in analytical overkill, employing either overly sophisticated techniques or exhaustive batteries of experiments which may not be necessary to answer the question(s) at hand. If the questions being asked can be confidently answered using basic techniques, then there is really no need to involve more extravagant analytical tools. If a question concerning a sample can be sufficiently answered using something as basic as a visual inspection, then there is no need to employ instrumentally based methodologies at all.
Since there is no single analytical tool capable of addressing the full spectrum of product surety needs, investigations assessing several different sample qualities will likely require multiple analytical techniques. In cases such as these, a progression of techniques may need to be employed, with careful evaluation of the data generated at each step to determine if additional information is needed. One can liken this to the peeling an onion, using each analytical tool at our disposal to successively remove layers of information about a sample, and in turn use that information to refocus the direction of the investigation. Additionally, the data generated by these various techniques should be used to cross-confirm where ever possible in order to build the level of confidence and detail in our conclusions.
Since the investigation of counterfeit pharmaceuticals has in the past primarily been the responsibility of law enforcement and government agencies, researchers may need to adjust how they conduct their work in order to meet the requirements of this new area of focus. Aspects of the investigation dealing with sample handling, chain of custody, sample retention and documentation may be new to the researcher. Workflows and infrastructure to address these issues may need to be developed. Counterfeit investigations in general present a unique challenge, since in many cases the analyst is tasked with identifying an unknown. The majority of scientists working for pharmaceutical or chemical manufacturers are involved with the characterization or confirmation of materials with identities and qualities which are known. Thus the analyst often has a clear understanding from the outset of an investigation of what to examine. In the investigation of a counterfeit pharmaceutical product, the analyst may be starting cold with no clear idea of what the sample is composed of or how to begin assessing it.
Several factors related to the overall requirements of the investigation and the nature of the sample itself will drive the decision making process. First, what is the timeline for generating data and providing an assessment of the product? Is information required the next day, in a few days or in a week or more? If results are required in a relatively short period of time, then certain techniques may be precluded from use. Next, what is the availability of sample material? Are several thousand tablets available or only a few milligrams of a powder? Is more sample available if the investigation consumes the initial aliquot? Techniques which will consume a significant amount of the available sample are generally less desirable. Investigations which may likely lead to litigation may require the preservation of as much sample as possible for use as evidence or for additional confirmatory testing. In general, non-destructive techniques are always preferred over destructive techniques. Is the information sought qualitative or quantitative in nature? If a tablet product is being investigated, is it enough to confirm the presence or absence of the active ingredient or is an accurate potency determination also required? Lastly, does the customer require information pertaining to the origin of the sample as well as its identity? If so, this may involve some very specialized techniques such as isotope ratio mass spectrometry4.
Analytical Techniques - The ‘Toolbox”
We have, in the modern analytical laboratory, a variety of tools to choose from for application to the problem at hand. The proper tool should be selected from this toolbox based on how well it can answer the question being asked, through the type of data it is capable of generating, all the while being mindful of each technique’s strengths and limitations. For the purposes of discussion, we have segregated our analytical toolbox into three distinct drawers, each based on the types of techniques found within.
Figure 1 - Comparison of Authentic Capsule Product (Bottom) to Counterfeit Product (Top)
The first includes those which are referred to as basic techniques. These would include techniques which do not involve sophisticated analytical instrumentation, or very basic instruments such as meters and balances. Included in this classification would be tests such as color and appearance, external dimension, weight difference or variance, hardness, friability and viscosity. These simple tests represent the first route for interrogation of a sample since they are fast, inexpensive, the data is often easy to interpret, and they can provide a wealth of important information concerning a sample. In some cases, a simple visual inspection may be all that is required to determine if a product is not genuine. Often times, a simple visual detection made in the field by a pharmacist, patient, doctor, etc. will trigger an investigation. Figure 1 represents a visual comparison of an authentic capsule product and a sample of a suspect counterfeit. As the image shows, the counterfeit capsule can be easily identified by the differences in appearance as compared to the authentic product.
Figure 2 - Comparison of Authentic Product Hologram (Left) to Counterfeit Hologram (Right) Under Magnification
Likewise, visual inspection can be extended beyond the actual dosage form to the products primary and secondary packaging components. Figure 2 shows the magnification of an authentic anti-counterfeiting hologram found on a secondary packaging component and a known fake. The differences in appearance are obvious and clearly indicate that this sample is not authentic. Additionally, differences in color or product consistency, evidence of tampering or previous use, and inconsistencies in product weight can all be used as indicators of authenticity. Unfortunately, these simple techniques provide no insight into the quality or efficacy of the sample.
Table 1 - Weight Difference and HPLC Potency Assay of Authentic and Suspect Capsule Drug Products
The second drawer contains techniques which would likely be found in any modern analytical laboratory, and which are traditionally utilized for the testing and release of drug products. These techniques would include gas and liquid chromatography, dissolution and Karl Fischer water assay to name a few. These techniques can provide data which is very specific to a particular product, including purity, enantiomeric purity, impurity profile, dissolution rate and moisture content. These techniques assess product characteristics which may not be easily replicated, and which are often a direct indication of the quality and efficacy of the product. Table 1 shows the results of a weight difference and HPLC potency assay conducted on two authentic capsule products and two suspect capsule products. The data indicate that not only did the suspect products exhibit poor uniformity in their weights but that the amount of active ingredient present, as measured via HPLC assay, was only ~25% of label claim. These data provide conclusive evidence that the suspect capsules are indeed counterfeit. Although many of the techniques found in this drawer of the toolbox are well known and commonly used, they may require high rates of sample consumption and lengthy analysis times.
The third drawer is likely the largest and deepest, containing a vast array of techniques which can be collectively referred to as spectroscopy. This includes such sub-disciplines as ultraviolet and visible, nuclear magnetic resonance, vibrational (mid and near infrared, Raman), mass spectrometry, X-ray diffraction, atomic absorption and laser induced breakdown spectroscopy, among many others. Each of these techniques is capable of generating information which is specific to a particular product, many providing data so specific that it is referred to as a “fingerprint” analysis. These techniques are capable of assessing product characteristics which are not easily replicated, and which are direct indicators of the quality or efficacy of the sample. Additionally, some of these techniques involve little if any sample preparation, low rates of sample consumption, with some being regarded as completely non-destructive, and having analysis times often on the order of a few minutes. However, some of these techniques may have limited availability in the analytical laboratory, due both to the intricacy and expense of the instrumentation itself and the lack of personnel trained in their use and interpretation of the data they generate. As a whole, spectroscopic techniques represent a bit of a mixed bag when considering their strengths versus limitations. However some of these techniques offer clear advantages due to their speed, efficiency and the specific data that they are capable of providing.
Figure 3 - Raman Spectra of Active Ingredient Polymorphs
Figure 4 - Raman Spectra of Two Drug Products
There are two spectroscopic techniques which deserve special mention for their potential use in the analysis of counterfeit pharmaceuticals. The first is Raman, a form of vibrational spectroscopy dealing with the inelastic scattering of light. In recent years, Raman has established itself as a primary technique for the detection of counterfeit pharmaceuticals due its broad range of applications, high level of specificity, speed, versatility and ease of use. Raman can provide useful information on most organic and some inorganic compounds, and is highly specific, enabling it to generate “fingerprint” type data. Raman is also capable in many instances of discriminating between polymorphs of crystal forms of an active ingredient, an especially useful capability when investigating counterfeit pharmaceuticals since a product’s authenticity may be verified through the detection of the crystal form of the active ingredient present. Figure 3 below shows the Raman spectra of two different polymorphs of an active ingredient, which are clearly different and easily distinguishable. In Figure 4, we see the Raman spectra of two drug products, the first being manufactured with Form I of the active ingredient while product two was manufactured using Form II. Comparing the active ingredient Raman spectra in Figure 3 to those of the drug products in Figure 4, unique responses for each form can be easily identified, confirming the presence of the specific polymorph used in each product.
A typical Raman analysis will involve little or no sample preparation, is in many cases non-destructive, and can be conducted in a matter of a few minutes. An additional advantage of using Raman for counterfeit analysis is the ability to collect data through packaging components and containers. High quality spectra can be generated through clear glass and many types of transparent or translucent plastics of varying thickness, preserving sample integrity. High quality, high resolution instruments are relatively affordable, robust, involve a low level of maintenance and overhead, and are user friendly. Raman capability can also be brought into the field if desired, with portable instruments now commercially available from several companies. Overall, Raman spectroscopy represents a powerful, flexible tool for the interrogation of suspected counterfeit pharmaceuticals.
Laser-induced breakdown spectroscopy (LIBS) is another technique which is well suited for the analysis of pharmaceutical counterfeits. In brief, LIBS is achieved by focusing a high-powered, short-pulse laser onto a sample surface to produce plasma that is rich in electrons, atoms and ions. The atoms and ions in the plasma emit radiation that is characteristic of the elemental composition of the sample. The unique advantages of LIBS that have contributed to widespread interest in the technique include remote sensing capabilities, in-situ analysis, little-to-no sample preparation, its micro-destructive nature, applicability to all media, simultaneous multi-element detection capability and relatively simple instrumentation. LIBS can fulfill various roles in the counterfeit drug identification toolbox. For instance, the depth profiling capability can be leveraged for coating analysis, yielding a spatially resolved method for comparing coating components in a suspect tablet relative to an authentic tablet. LIBS can also be used to rapidly identify the presence of toxic metals that may have been used in the preparation of the counterfeit pharmaceutical, or which may be present as an impurity in one of the components of the product. Other applications of LIBS in counterfeit identification and characterization include determining the extent of excipient or active ingredient homogeneity within a sample or between a batch of samples, and quantification of elemental components for comparison to a control. Regardless of the application, LIBS offers an attractive combination of advantages over other more traditional techniques in our tool box, including rapid analysis time, little-to-no sample preparation and minimal sample destruction.
Conclusion
As the global market for counterfeit pharmaceuticals continues to expand, counterfeits will become more sophisticated and harder to discriminate from authentic products. Regulatory agencies and the pharmaceutical industry are bringing new technologies to bear against this problem, such as 2D barcodes, micro-printing, proprietary dyes and inks and radio frequency identification tags. Several of these technologies may be implemented in combination, making up a total e-pedigree or track and trace program aimed at preventing the entry of counterfeits into the drug supply chain. However, since it is unrealistic to assume that we will ever have 100% exclusion of counterfeit pharmaceuticals from the global drug market, there will likely always be a need for good laboratory capabilities aimed at their detection. As counterfeiting activities become more sophisticated, the need for more selective and discriminating analytical and forensic techniques to ensure patient safety and product integrity grows. The continuing advancement and refinement of existing instrument technologies, as well as the introduction of new techniques will enable the analytical laboratory to stay one step ahead of the counterfeiters. A flexible, multidisciplinary laboratory program, utilizing a broad range of analytical techniques, will be required to successfully interrogate a suspect sample and keep inefficacious and unsafe products out of the medicine cabinets of patients.
References
- Lawrence Hardie, “Counterfeit Drugs are a Danger to Everyone,” DrugNewswire, July 14, 2006.
- A. M. Dondorp et al., “Fake Antimalarials in Southeast Asia are a Major Impediment to Malaria Control,” Tropical Medicine and International Health, Vol. 9 No. 12 (December, 2004): 1241
- Randall W. Lutter, Ph. D., Statement before Subcommittee on Criminal Justice, Drug Policy and Human Resources, November 1, 2005, www.fda.gov/ola/2005/counterfeit1101.html
- John P. Jasper et al., “Stable Isotopes Provide a New PAT Tool,” Pharmaceutical Manufacturing, Vol. 4 No. 5 (2005): 28