Counterfeit Cialis and Viagra fingerprinting by ATR-FTIR spectroscopy with chemometry: Can the same pharmaceutical powder mixture be used to falsify two medicines?

This paper proposes a direct and efficient method to discriminate between counterfeit and authentic Cialis and Viagra samples by combining attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy with multivariate techniques. The chemical profile of 53 commercial samples (Viagra®, Cialis®) and 104 counterfeit samples (Viagra and Cialis) from distinct seizures were obtained from ATR-FTIR data derived from 10 mg of crushed core tablets. Principal component analysis (PCA) technique was employed to classify samples based on the fingerprint region mid-infrared spectra (1800–525 cm−1) using OMNIC v.7.2 software; PCA enabled categorizing samples in groups with different chemical profiles, successfully distinguishing between authentic and counterfeits samples in forensic routine. The existence of active pharmaceutical ingredients (API) and technological adjuvant others than specified on the medicine package were also detected in counterfeit samples. In addition, we applied the similarity match (SM) method to demonstrate that a mixture of pharmaceutical powders deriving from a common origin may have been used to manufacture both counterfeit Cialis and Viagra tablets from distinct seizures.