Screening suspected counterfeit Viagra® and imitations of Viagra® with near-infrared spectroscopy

Abstract

We describe a near-infrared spectroscopy (NIRS) method for fast-screening Viagra tablets, counterfeit Viagra tablets, and imitations of Viagra. The method can (1) check the homogeneity of a batch; (2) distinguish counterfeits and imitations from authentic Viagra; (3) screen for the presence of sildenafil citrate, the pharmacologically active substance in Viagra, irrespectively of the excipients present; (4) and detect whether similar samples have been previously analysed. We applied the method to 103 samples with a diversity of appearance, chemical composition, and origin. Other analytical methods confirmed the positive screening results for sildenafil citrate and the presence of other pharmacological active substances. The NIRS screening indicated the absence of sildenafil citrate in the presence of another pharmacological substance for only 2 samples, where the reference methods showed the presence of sildenafil citrate in addition to that of clomifene citrate. Otherwise, the method gave no false positive or negative results. The NIRS screening method is very fast and reliable for detecting counterfeits and imitations, and it correctly predicts the presence or absence of sildenafil citrate in 98% of the samples.

The usefulness of 2D DOSY and 3D DOSY‐COSY 1H NMR for mixture analysis: application to genuine and fake formulations of sildenafil (Viagra)

“…Screening between imitation and authentic Viagra was also described using NIR spectroscopy combined with wavelength correlation and principal component analysis. [15] The time of analysis is very short, the technique is nondestructive and no pretreatment of the formulation is required. However, it does not provide information on the excipients (except talc), is not quantitative and needs classical analytical methods (TLC, UV-vis spectrophotometry, HPLC-DAD, LC-DAD-MS 2 ) for identification and quantitation of actives.…”

“…Vredenbregt et al [15] described a near-infrared (NIR) spectroscopy method used to check the homogeneity of a batch, distinguish counterfeits and imitations from authentic Viagra, and screen for the presence of sildenafil citrate in 103 samples with a diversity of appearance, chemical composition and origin. Maurin et al [16] screened seven Viagra samples with a X-ray powder diffraction method which correctly predicts the presence or absence of sildenafil and/or particular excipients.…”

Detection of counterfeit Viagra® by Raman microspectroscopy imaging and multivariate analysis

“…applied NIR spectroscopy on 103 samples to detect counterfeit Viagra ® but also to check the homogeneity of batches and screen the presence of sildenafil citrate [6]. De Veij et al…”

Spectroscopic and Chemometric Analysis of Illegally Manufactured Formulations of Selected Medicines

“…Most of the uncovering the adulteration studies focused on both drugs Viagra and Cialis. For this purpose XRD, Raman spectroscopy, NIR, FT-IR, DOSY 1 HNMR and other analytical methods were reported in literature for detecting the illegally manufactured drugs especially Viagra and Cialis [4][5][6][7][8][9][10][11] . In this study Cipram ® , Panadol extra ® , Xenical ® will be investigated.…”