Figure 4

Variability in sensitivity of marketed PCP and tricyclic antidepressant screening immunoassays. The plotted circles indicate the concentration of compound that produces equivalent reaction to 25 ng/mL PCP or 1000 ng/mL desipramine (tricyclic antidepressant assays). The dashed lines bracket clinically or toxicologically relevant concentrations from studies in the published literature (see text of Results for detailed description). A) PCP assays. Marketed PCP assays have varying degrees of cross-reactivity with dextromethorphan, meperidine, thioridazine, and mesoridazine. The brackets for PCP correspond to urine concentrations observed in patients abusing PCP[54] B) TCA assays. Marketed TCA screening immunoassays have similar cross-reactivities to TCAs but variable cross-reactivity to carbamazepine, phenothiazines (such as prochlorperazine), and quetiapine. The marketed TCA assays include those approved for serum/plasma or urine samples.