Objective: To assess potential nonadherence among patients prescribed antipsychotic agents and identify the use of illicit substances and/or nonprescribed medications in these patients. Methods: Urine samples that were submitted to the laboratory from patients prescribed antipsychotic medications were analyzed for the presence of antipsychotics, illicit substances (marijuana metabolite [THC] and/or cocaine metabolite [benzoylecgonine]), and nonprescribed opioid or benzodiazepine medications. Samples were classified as positive for the antipsychotic if either parent drug and/or metabolite(s) were confirmed and negative if neither were detected. Antipsychotic medications were tested using liquid chromatography/tandem mass spectrometry. Other drugs were tested using mass spectrometry confirmation following a presumptive screening result. Results: A total of 22,951 samples were analyzed. The average age was 42.3 years, women provided 51.6% of samples, and the primary payor was Medicaid or Medicare (72.3% of samples). Overall, 24.8% of samples tested negative for an antipsychotic drug prescribed to the patient and 6.5% tested positive for a nonprescribed antipsychotic. Rates of nonadherence varied by antipsychotic medication and were greatest for haloperidol (37.0%) and lowest for clozapine (4.4%) and paliperidone (7.2%). Nonprescribed opioids/benzodiazepines and/or illicit drugs were significantly more likely to be found in samples from patients who tested negative versus positive for a prescribed antipsychotic medication (41.3% vs 32.8%; odds ratio, 1.44; 95% confidence interval, 1.35-1.54). Conclusions: Urine drug monitoring may be of value both for monitoring adherence to antipsychotic therapy and for detecting signals of potential substance abuse.
Mancia Ko, PharmD
Michael DeGeorge, PharmD
Patricia Woster, PharmD
Thomas Smith, MD
Ingenuity Health, a service of Ameritox Ltd.