Correlation between assessment of cytochrome P450 1A2 activity and enzyme activity scores, and their relation with clozapine exposure.

Correlation with clozapine concentrations showed the advantage of the 17X/137X ratio over the CCS in clozapine dose optimisation. CYP1A2 activity, especially when determined by the caffeine probe, may be used to personalise clozapine dosing for patients experiencing treatment failure.