Physicochemical and chemometric profiling of counterfeit Captagon tablets for seizure comparison and forensic...

Counterfeit Captagon tablets trafficked throughout the Near and Middle East rarely contain the original active ingredient, fenethylline. Instead, they commonly contain amphetamine and pharmacologically active adulterants. Whether tablet color and logo/shape reflect the underlying chemical profile remains unclear.

A Primary Dataset of 50 tablets and an Independent Comparison Dataset of 31 tablets, derived from different submissions within a six-seizure collection from Jordan, were evaluated alongside case-level adulterant records covering 651 submitted tablets. Physical characteristics and semiquantitative gas chromatography-mass spectrometry profiles, expressed as normalized chromatographic peak-area percentages, were examined using correlation analysis, principal component analysis, hierarchical cluster analysis, one-way analysis of variance, Tukey post hoc comparisons, Kruskal-Wallis analysis, and a laboratory-prefix sensitivity analysis.

The multivariate analyses showed substantial overlap among color and logo/shape groups. In the Primary Dataset, diphenhydramine normalized peak-area percentage differed among logo/shape categories (F(3, 43) = 8.80, p < 0.001, η² = 0.38), although 62% of the variance remained unexplained and the distributions overlapped. Tukey, Kruskal-Wallis (H = 17.95, p < 0.001), and laboratory-prefix sensitivity analyses supported the association. Caffeine, theophylline, and acetaminophen occurred in all six seizure cases, while several constituents differed between the tablet datasets.

Tablet color did not provide a useful indication of chemical profile. Logo/shape showed a dataset-specific association with diphenhydramine, but group overlap and unavailable logo information for the comparison dataset precluded predictive or externally validated classification. Physical documentation may complement, but cannot replace, instrumental chemical profiling in forensic seizure comparison.