Sir: The recent introduction of this technique (Reference CoatesCoates, 1999) has led to an important development in psychiatric practice in our area, with possible national consequences.

At a recent mental health review tribunal, due to the fact that a patient had consistently tested negative for olanzapine it was accepted that the patient was not adherent with treatment, contrary to their assertion. The presence of objective evidence of non-adherence was, I believe, instrumental in the tribunal's decision to continue a detention order. Therefore, this shows that there are considerable implications of regular testing for olanzapine, and possibly other antipsychotics, in urine. Within the context of judicial or semijudicial processes, objectively testable evidence will, I believe, always have a greater weight than that of subjective opinion. I therefore believe that urinary detection of olanzapine has been confirmed as an aid to adherence. The issue of whether adherence then becomes compulsion is something that will require further consideration.