The EMs and PMs of CYP2D6 treated with tramadol behaved differently in static and dynamic pupillometry. The reason for this could largely be explained with the aid of the metaboliser status and the pharmacokinetic properties of tramadol. In EMs, the pupillometric response was mainly driven by the (+)-M1, which comprises the mu action component of tramadol; whereas, in PMs, the non-mu component appears to play an important role. Thus, pupillometry was found to be useful in pharmacodynamic profiling and provides a good correlation with the pharmacokinetics.

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An achiral and chiral separation for the determination of tramadol and its main metabolite O-demethyltramadol in urine samples by CE with UV detection was developed. It was possible to separate tramadol and its phase I and phase II metabolites in one single run using a borate buffer. Furthermore, the simultaneous chiral separation of tramadol and the phase I metabolites was achieved using carboxymethyl-beta-cyclodextrin as chiral selector. To reach the required limits of quantification for the analytes, a preconcentration by solid-phase extraction for the achiral assay and by liquid-liquid extraction for the chiral assay was used. The methods were validated and their applicability was shown by the determination of tramadol and O-demethyltramadol in urine samples.

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