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Combined Thermal and Colorimetric Analysis as a Tool for Detecting Counterfeit Viagra® Tablets.

Paweł Ramos1, Sławomir Wilczyński2, Klaudia Stocerz1,3

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Summary

Counterfeit Viagra® and darknet sildenafil tablets show significant variability in quality and authenticity. Combined thermal and colorimetric analysis effectively detects falsified medicines, highlighting risks of illegal drug purchases.

Keywords:
CIE L*a*b*Viagra®colorimetrycounterfeit drugsdarknetsildenafilthermal analysis

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Area of Science:

  • Pharmaceutical Analysis
  • Forensic Chemistry
  • Materials Science

Background:

  • Analysis of counterfeit pharmaceuticals is crucial for public health and safety.
  • The darknet presents a significant challenge for law enforcement in controlling illicit drug markets.
  • Original Viagra® (sildenafil citrate) is a widely counterfeited medication.

Purpose of the Study:

  • To comparatively analyze original Viagra® with sildenafil tablets from the darknet.
  • To assess the physicochemical properties and authenticity of illicitly sourced sildenafil.
  • To evaluate the efficacy of thermal and colorimetric methods for counterfeit drug detection.

Main Methods:

  • Thermogravimetry (TG), Derivative Thermogravimetry (DTG), and calculated Differential Thermal Analysis (c-DTA) for thermal stability and decomposition profiling.
  • Colorimetric analysis using the CIE L*a*b* system for objective visual comparison.
  • Comparative analysis against original Viagra® reference standards.

Main Results:

  • Most darknet samples exhibited significant variability in thermal profiles and color, indicating poor quality control.
  • Only a few samples (V1, V3, V4, V6, V8) showed similarities to original Viagra®.
  • Samples V2 and V7 deviated markedly, suggesting potential absence or altered chemical form of sildenafil.

Conclusions:

  • Integrated thermal and colorimetric analyses are effective for identifying counterfeit pharmaceuticals.
  • Physicochemical inconsistencies in darknet samples highlight the risks associated with illegal drug sources.
  • The study validates the use of combined analytical techniques for detecting falsified medicines.