Screening for hydroxylation and acetylation polymorphisms in man via simultaneous analysis of urinary metabolites of mephenytoin, dextromethorphan and caffeine by capillary electrophoretic procedures.

Phenotypes for hydroxylation can be predicted by using mephenytoin and dextromethorphan as substrates, whereas phenotypes for acetylation can be determined with caffeine as probe drug. After single-dose administration of one of these drugs, of two of them simultaneously, or of the three drugs together, the major urinary metabolites (4-hydroxymephenytoin; dextrorphan, 3-methoxymorphinan, 3-hydroxymorphinan; 5-acetylamino-6-amino-3-methyluracil as decomposition product of 5-acetylamino-6-formylamino-3-methyluracil, 1-methylxanthine, respectively) of these substrates were analyzed by capillary electrophoretic techniques. No sample pretreatment other than enzymatic hydrolysis of the conjugated compounds was applied. Assays based on micellar electrokinetic capillary chromatography are shown to allow simultaneous and unambiguous phenotyping with mephenytoin and dextromethorphan or mephenytoin and caffeine. Simultaneous screening for all three polymorphisms with a single injection of a hydrolyzed urine is shown to be possible via use of multiwavelength absorption detection only. Phenotypes determined by electrokinetic capillary techniques are shown to agree with those obtained by analysis with customary assays based on high-performance liquid chromatography.