Comparison of multivariate calibration methods to determine simultaneously mebendazole-cambendazole and mebendazole-thiabendazole in pharmaceutical preparations by UV-visible spectrophotometry.

Three multivariate calibration methods, Principal Component Regression (PCR), the K-matrix method and Q-mode factor analysis followed by varimax and Imbrie's oblique rotations were applied to the simultaneous spectrophotometric determinations of mebendazole (MBZ)-cambendazole (CBZ) and thiabendazole (TBZ)-mebendazole in commercial samples of Exelmin and Helmiben. The calibration set concentrations were selected to contain a +/-10% variation in the quantity of active ingredients as declared by the manufacturer. The Q-mode factor analysis provides superior results for the two pharmaceutical formulations. The K-matrix method proved to be totally inadequate for these determinations. Almost all Q-mode results have relative errors much smaller than 5% of the active ingredient contents. This investigation shows that PCR and Q-mode factor analysis can be used to determine MBZ-CBZ and TBZ-MBZ in commercial drugs.

Cambendazole and nondrug macromolecules in tissue residues.

The anthelmintic cambendazole is rapidly metabolized to at least 13 urinary metabolites. Radioactivity was found in liver for weeks after a single dose in cattle, but even at 3 days' withdrawal, cambendazole and metabolites previously identified in urine accounted for only a small fraction of liver radioactivity. The radioactivity was ubiquitously distributed in protein and nucleic acid fractions, and [14C] glutamic acid was identified, indicating incorporation of 14C into the endogenous pool. Part of the residual liver radioactivity at 7 days was convertible chemically to 5-nitrobenzimidazole, indicating a drug-related macromolecular residue. However, data from rats fed radiolabeled steer liver indicate that the residue is minimally bioavailable and therefore of substantially less toxicological concern than cambendazole itself.