Clozapine is an important drug in the treatment of schizophrenia, and adherence is generally thought to be as good as, if not better than, other antipsychotics. Nonadherence, however, is difficult to detect and potentially dangerous. Tolerance to the cardiovascular effects of the drug is easily lost; restarting at a “normal” dose can prove fatal after a period of abstinence. Nonadherence also increases the risk of self-harm. In this podcast, Dr. Robert Flanagan, a now-retired clinical scientist at Kings College Hospital in London, discusses his study of nonadherence, as measured by plasma levels of clozapine, in samples submitted to a clozapine therapeutic drug monitoring service from 1993–2017. In thousands of submitted samples, nonadherence was 1.1% for men and 1% for women. Dr. Flanagan discusses both the implications of his research as well its limits. The research is published in the September–October 2023 issue of the Journal of Clinical Psychopharmacology, in an article titled “Assessing Adherence to Clozapine: Practical Considerations.” Dr. Flanagan’s coauthors are Samora Hunter and Stephen J. Obee, also of Kings College Hospital.