Comparison of genuine, generic, and counterfeit Cialis tablets using vibrational spectroscopy and statistical methods (2021)
Dita Spálovská, Tomáš Pekárekb, Martin Kuchař ,Vladimír Setnička
Abstract
The dubious online market in phosphodiesterase type 5 inhibitors is growing on a global scale. Counterfeit medical products can represent health issues for the user and cause medical mistrust. Within this work, genuine Cialis containing the active pharmaceutical ingredient (API) tadalafil, its generics available in the Czech Republic, and the Cialis tablets from questionable online pharmacies were analyzed. The methods of infra-red and Raman spectroscopy were used for the identification of the counterfeit tablets and for the verification of their API and excipients. All 9 tablets from online pharmacies were counterfeit with 2 of them even containing a different API (sildenafil, vardenafil). In addition, Raman mapping was used to determine the API and excipients’ distribution and, in combination with multivariate data analysis, to separate similar tablets in clusters and to identify the outliers. Scanning electron microscopy of the samples revealed that the process of a wet granulation of micronized API was used during the formulation of the tablets. This comprehensive approach of analysis can be used for advanced exploration of the dubious samples of various medical products.
1. Introduction
According to the OECD [1] and World Health Organization (WHO) [2], medicines for erectile dysfunction treatment are among the most frequently counterfeited. The main representatives of these lifestyle drugs, which act as inhibitors of phosphodiesterase type 5 (PDE5), are primarily Viagra with sildenafil citrate as its active pharmaceutical ingredient (API), Cialis with tadalafil as its API, Levitra with vardenafil, and Spedra with avanafil. The advantage of Cialis over other PDE5 inhibitors is in the duration of action in the human organism – it has a terminal half-time of approximately 17.5 h in comparison to approximately 4–6 h for Viagra, Levitra, and Spedra. The increasing phenomenon of counterfeit medicines is caused mostly by illegal online pharmacies where everyone can buy those prescription-only medicines without the embarrassment of consulting a doctor. The second advantage of ordering those counterfeits via online pharmacies for patients is a lower price than the price of the genuine medicine in a regular pharmacy but in comparison with the generic equivalent tablets, the price is similar. However, their unknown origin and composition may cause a potential health risk [3].
Substandard and counterfeit medical products, as defined by the WHO in 2017 [4], have an impact not only on the individual’s health but also on the economy, families, national health systems as well as on pharmaceutical companies. Moreover, the poor quality of such medical products often caused by not following good manufacturing practices (GMP) could arouse mistrust for medicines in general. A comprehensive analysis of these dubious medical products is highly desirable as well as education of the general public about the dangers of purchasing medicines online.
In general, experts in the pharmaceutical field in cooperation with the WHO and national institutes of health are suggesting simple and also sophisticated forensic chemistry techniques to detect, screen, and analyze counterfeit medical products [5,6]. Beside visual inspection [7], the methods of thin-layer chromatography (TLC) [8], colorimetry [9], chromatographic techniques [10,11], nuclear magnetic resonance (NMR) [12,13], X-ray fluorescence spectrometry [14], X-ray powder diffraction (XRD) analysis [15] and infra-red (IR) and Raman spectroscopy [16–22] are highly recommended. Several analytical methods have also been used to distinguish between counterfeit medical products of PDE5 inhibitors and genuine products. Vibrational spectroscopy is one of those with the highest application potential in pharmacy for its reliability, speed, minimal (or no) need for sample preparation, and non-destructiveness [23,24]. Another promising tool for the analysis of counterfeit tablets is Raman mapping, which enables a detailed analysis of the tablet composition and spatial distribution [25]. Moreover, in combination with multivariate data analysis, it could help to reveal more significant modifications during the counterfeiting of tablets [26,27]. Furthermore, when deciding which analytical method to choose (Fig. 1), vibrational spectroscopy combined with statistical methods is unique among separation methods and NMR in its capability of components and particle size distribution, which is highly desirable for the pharmaceutical industry. This method has already been used for the analysis of the counterfeit Viagra tablet core [28,29] and provided information on the particle distribution, size as well as excipients used and even for a simple analysis of two counterfeit Cialis tables [30]. However, there is still a lack of detailed studies on other PDE5 inhibitors using Raman mapping.
Our intent was to combine the common methods of IR and Raman spectroscopy and explore the possibilities of an innovative approach for reliable Raman imaging of the Cialis tablets in connection with the statistical method based on using the principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA). The aim was to distinguish between the counterfeit medical products and the genuine or generic medicines, to examine their quality, to identify the APIs and the excipients used, to determine the particle size distribution, and to inspect the dubious online market in Cialis which is a prescription-only medical product in the Czech Republic. Furthermore, we analyzed the samples using scanning electron microscopy (SEM) to confirm the mechanisms of their formulation and to verify the API distribution from Raman mapping.
4. Conclusion
In this study, we have focused on an analysis of genuine Cialis, its generics available in the Czech Republic, and the Cialis tablets purchased from dubious online pharmacies. The aim was to investigate the online market with Cialis, detect the counterfeit tablets, identify the APIs and excipients used in those tablets and compare them with the genuine medicines also containing 20 mg of tadalafil as an API.
Our comprehensive approach embraced the methods of IR and Raman spectroscopy, SEM, and Raman mapping along with the multicomponent statistical method PCA to explore each tablet. All the Cialis tablets from dubious online pharmacies were counterfeit while two (tablets A and B) of the nine samples even contained a different API (sildenafil and vardenafil). Those tablets were excluded from further PCA. Even if the IR and Raman spectra of the ground tablets were very similar to genuine Cialis in four cases, Raman mapping provided reliable discrimination of all counterfeit tablets. Besides, PCA supported by SIMCA applied to the Raman mapping data allowed separation of the individual clusters of the generics and counterfeit Cialis tablets according to their different chemical profiles and distinguished successfully between the genuine, generic, and counterfeit Cialis samples. Using SEM, the wet granulation of micronized tadalafil was identified as the formulation method for the counterfeit tablets.
Routine analysis is usually not able to detect well-made counterfeit medical products. The proposed combination of several analytical methods together with statistical evaluation is much more reliable. Moreover, the information obtained by Raman mapping is important not only for the identification of the counterfeit but also for determining the formulation process used, the distribution, and the particle size or clusters of API and excipients. This information can be especially valuable for generic pharmaceutical companies looking to draw ideas for their manufacturing process. In addition, the knowledge of particle distribution can help to identify unauthorized products.
The proposed combination of different methods for the analysis of the dubious medical products resulted in a comprehensive approach for gaining maximum information about the samples.
Dita Spálovská, Tomáš Pekárekb, Martin Kuchař ,Vladimír Setnička
Abstract
The dubious online market in phosphodiesterase type 5 inhibitors is growing on a global scale. Counterfeit medical products can represent health issues for the user and cause medical mistrust. Within this work, genuine Cialis containing the active pharmaceutical ingredient (API) tadalafil, its generics available in the Czech Republic, and the Cialis tablets from questionable online pharmacies were analyzed. The methods of infra-red and Raman spectroscopy were used for the identification of the counterfeit tablets and for the verification of their API and excipients. All 9 tablets from online pharmacies were counterfeit with 2 of them even containing a different API (sildenafil, vardenafil). In addition, Raman mapping was used to determine the API and excipients’ distribution and, in combination with multivariate data analysis, to separate similar tablets in clusters and to identify the outliers. Scanning electron microscopy of the samples revealed that the process of a wet granulation of micronized API was used during the formulation of the tablets. This comprehensive approach of analysis can be used for advanced exploration of the dubious samples of various medical products.
1. Introduction
According to the OECD [1] and World Health Organization (WHO) [2], medicines for erectile dysfunction treatment are among the most frequently counterfeited. The main representatives of these lifestyle drugs, which act as inhibitors of phosphodiesterase type 5 (PDE5), are primarily Viagra with sildenafil citrate as its active pharmaceutical ingredient (API), Cialis with tadalafil as its API, Levitra with vardenafil, and Spedra with avanafil. The advantage of Cialis over other PDE5 inhibitors is in the duration of action in the human organism – it has a terminal half-time of approximately 17.5 h in comparison to approximately 4–6 h for Viagra, Levitra, and Spedra. The increasing phenomenon of counterfeit medicines is caused mostly by illegal online pharmacies where everyone can buy those prescription-only medicines without the embarrassment of consulting a doctor. The second advantage of ordering those counterfeits via online pharmacies for patients is a lower price than the price of the genuine medicine in a regular pharmacy but in comparison with the generic equivalent tablets, the price is similar. However, their unknown origin and composition may cause a potential health risk [3].
Substandard and counterfeit medical products, as defined by the WHO in 2017 [4], have an impact not only on the individual’s health but also on the economy, families, national health systems as well as on pharmaceutical companies. Moreover, the poor quality of such medical products often caused by not following good manufacturing practices (GMP) could arouse mistrust for medicines in general. A comprehensive analysis of these dubious medical products is highly desirable as well as education of the general public about the dangers of purchasing medicines online.
In general, experts in the pharmaceutical field in cooperation with the WHO and national institutes of health are suggesting simple and also sophisticated forensic chemistry techniques to detect, screen, and analyze counterfeit medical products [5,6]. Beside visual inspection [7], the methods of thin-layer chromatography (TLC) [8], colorimetry [9], chromatographic techniques [10,11], nuclear magnetic resonance (NMR) [12,13], X-ray fluorescence spectrometry [14], X-ray powder diffraction (XRD) analysis [15] and infra-red (IR) and Raman spectroscopy [16–22] are highly recommended. Several analytical methods have also been used to distinguish between counterfeit medical products of PDE5 inhibitors and genuine products. Vibrational spectroscopy is one of those with the highest application potential in pharmacy for its reliability, speed, minimal (or no) need for sample preparation, and non-destructiveness [23,24]. Another promising tool for the analysis of counterfeit tablets is Raman mapping, which enables a detailed analysis of the tablet composition and spatial distribution [25]. Moreover, in combination with multivariate data analysis, it could help to reveal more significant modifications during the counterfeiting of tablets [26,27]. Furthermore, when deciding which analytical method to choose (Fig. 1), vibrational spectroscopy combined with statistical methods is unique among separation methods and NMR in its capability of components and particle size distribution, which is highly desirable for the pharmaceutical industry. This method has already been used for the analysis of the counterfeit Viagra tablet core [28,29] and provided information on the particle distribution, size as well as excipients used and even for a simple analysis of two counterfeit Cialis tables [30]. However, there is still a lack of detailed studies on other PDE5 inhibitors using Raman mapping.
Our intent was to combine the common methods of IR and Raman spectroscopy and explore the possibilities of an innovative approach for reliable Raman imaging of the Cialis tablets in connection with the statistical method based on using the principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA). The aim was to distinguish between the counterfeit medical products and the genuine or generic medicines, to examine their quality, to identify the APIs and the excipients used, to determine the particle size distribution, and to inspect the dubious online market in Cialis which is a prescription-only medical product in the Czech Republic. Furthermore, we analyzed the samples using scanning electron microscopy (SEM) to confirm the mechanisms of their formulation and to verify the API distribution from Raman mapping.
4. Conclusion
In this study, we have focused on an analysis of genuine Cialis, its generics available in the Czech Republic, and the Cialis tablets purchased from dubious online pharmacies. The aim was to investigate the online market with Cialis, detect the counterfeit tablets, identify the APIs and excipients used in those tablets and compare them with the genuine medicines also containing 20 mg of tadalafil as an API.
Our comprehensive approach embraced the methods of IR and Raman spectroscopy, SEM, and Raman mapping along with the multicomponent statistical method PCA to explore each tablet. All the Cialis tablets from dubious online pharmacies were counterfeit while two (tablets A and B) of the nine samples even contained a different API (sildenafil and vardenafil). Those tablets were excluded from further PCA. Even if the IR and Raman spectra of the ground tablets were very similar to genuine Cialis in four cases, Raman mapping provided reliable discrimination of all counterfeit tablets. Besides, PCA supported by SIMCA applied to the Raman mapping data allowed separation of the individual clusters of the generics and counterfeit Cialis tablets according to their different chemical profiles and distinguished successfully between the genuine, generic, and counterfeit Cialis samples. Using SEM, the wet granulation of micronized tadalafil was identified as the formulation method for the counterfeit tablets.
Routine analysis is usually not able to detect well-made counterfeit medical products. The proposed combination of several analytical methods together with statistical evaluation is much more reliable. Moreover, the information obtained by Raman mapping is important not only for the identification of the counterfeit but also for determining the formulation process used, the distribution, and the particle size or clusters of API and excipients. This information can be especially valuable for generic pharmaceutical companies looking to draw ideas for their manufacturing process. In addition, the knowledge of particle distribution can help to identify unauthorized products.
The proposed combination of different methods for the analysis of the dubious medical products resulted in a comprehensive approach for gaining maximum information about the samples.
