Antipsychotic Plasma Levels in Schizophrenia: Detecting Nonadherence and Guiding Dose Decisions

Joseph F. Goldberg, MD, in this installment of "Brain Trust: Conversations in Psychopharmacology," sits down with Jonathan Meyer, MD, to discuss therapeutic drug monitoring of antipsychotics in schizophrenia spectrum disorders. Meyer explains why measuring plasma concentrations can replace guesswork about nonresponse, how population dose-level relationships allow clinicians to predict an expected 12-hour trough, and why a level well below expectation most often points to nonadherence. The conversation distinguishes a response threshold from a truly therapeutic level and describes the point of futility, beyond which a tolerated but ineffective level is unlikely to convert a nonresponder. Meyer describes how antipsychotic response begins early and accumulates over time, so that for a given oral dose most of the positive symptom benefit emerges within 2 weeks and little is added after 4.^1,2 Goldberg and Meyer also consider the relatively forgiving therapeutic index of modern antipsychotics, family history-informed clozapine titration, and why a measured level may be more informative than pharmacogenetic testing.