Comparison of Authentic and Suspect Pharmaceuticals - Pharmaceutical Technology

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Comparison of Authentic and Suspect Pharmaceuticals
The authors applied near-infrared (NIR) spectrophotometry to assess whether eight drug products were authentic or counterfeit.

Pharmaceutical Technology
Volume 33, Issue 8, pp. 46-52

Results and discussion

Figure 2. Panel A shows the test Cialis 20-mg product (left) and the reference Cialis 20-mg product (right). Panel B shows the two sides of a test Cialis 50-mg product, where one side (right) exhibited poor engraving.
Visual inspection. In all cases, simple visual inspection indicated that the test product appeared authentic, compared with the reference product, except for the test product labeled Cialis 50 mg. Figure 1 shows the test Cialis 50 mg package. Figure 2 shows the test Cialis 20 mg tablet, reference Cialis 20 mg tablet, and test Cialis 50 mg tablet. The packaging for the test product labeled Cialis 50 mg, included a "Lilly" hologram and a misspelled "Lieel icos" marking. The plastic container was of low quality and failed to denote tablet quantity, the manufacturer, and the distributor.

Figure 3. Near-infrared spectra of Cialis 20 mg test and reference products and the test Cialis 50-mg product.
It should be emphasized that simple visual inspection is the dominant screening method for potentially counterfeit products. Arguably, simple visual inspection is conducted on every pharmaceutical product dispensed from a pharmacy.

Figure 4. Near-infrared spectra of Lamisil 250 mg test and reference products.
NIR spectra comparison. Figures 3–9 show the NIR spectra of test and reference products from an RCA XDS NIR spectrometer. Results from a PHAZIR-Rx instrument provided comparable results. Only mean profiles were plotted because the spectra for each product varied little. Visual inspection of spectra showed all test spectra to be similar to the correseponding reference spectra, except that of test Cialis 50 mg and test Norvasc 10 mg. Because Cialis 50 mg is not marketed in the US, it was compared with reference Cialis 20 mg. Examination of the peaks in Figure 3 showed peak shifts at 422, 473, 636, 900, 1200, 1485, 1564, 2100, and 2354 nm. Shifts in peak position indicate differences in chemical composition. Given the number of significant spectral differences, it is highly unlikely that the Cialis 50 mg is an authentic product. It should be emphasized that this conclusion stems from using NIR to screen products for authenticity without direct assistance from the manufacturer or the Hong Kong regulatory authority.

Figure 5. Near-infrared spectra of Levitra 20 mg test and reference products.
Not surprisingly, the spectra for the authentic generic amlodipine besylate 10 mg did not match that of the reference Norvasc 10 mg (see Figure 7). Generic amlodipine besylate was manufactured by Mylan Laboratories (Canonsburg, PA). Though the generic amlodipine besylate is presumably authentic, generics typically contain different excipients than do the references, so it is not surprising that the spectra are slightly different. The vast majority of the tablet's ingredients are excipients. Furthermore, the manufacturing processes of the generic and branded product differ, thus resulting in further differences in physical attributes and increased spectral differences.

Figure 6. Near-infrared spectra of Norvasc 5 mg test and reference products.
Figure 7 compares test Norvasc 10 mg with reference Norvasc 10 mg. Spectra were insufficient to determine whether the test product was authentic.


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