Therapeutic drug monitoring (TDM) during maintenance phase treatment at a community mental health centre

Objective: To assess the extent to which therapeutic drug monitoring during maintenance phase treatment with lithium and clozapine was performed according to an agreed protocol and to identify strategies that may support monitoring. Methods: Data concerning the prescribing and monitoring patterns of lithium for 31 patients and clozapine for 53 patients were collected retrospectively over a period of 2 years. Results: Adherence to clozapine monitoring throughout the study period was 90.5%, while the monitoring of lithium was less likely at 58.1% (P < 0.001). While those prescribed lithium were less likely to adhere to prescribed dosing than those prescribed clozapine (P < 0.007), they were also more likely to have a change of medication (P < 0.005) and require admission to inpatient care (P < 0.002). Conclusions: Despite the initiatives established to improve adherence to monitoring, there was a significantly lower level of lithium monitoring compared to that of clozapine. Strategies that are likely to support monitoring include the use of labels to clarify tests required, the use of a database to keep track of those requiring pathology tests and allocation of time each week for a nurse to work with medical staff and case managers to support monitoring