Therapeutic drug monitoring of lithium in patients with bipolar affective disorder: experiences from a tertiary care hospital in India.

Lithium continues to be a main drug in mood disorders despite risks associated with high blood levels of lithium and introduction of a number of mood stabilizers. Therapeutic drug monitoring (TDM) is a norm while using lithium. The present paper reports analysis of a retrospective audit of TDM of lithium over a period of 4 years. A retrospective serum lithium estimation data of 4 years were analyzed for drug levels, reasons for request, and correlation of levels with dose and side effects. Of 4359 requests received during the study period, about 80% were for routine monitoring and about 3% each were for adverse effects and relapse or irregular treatment. Twelve percent of the requisition forms were incomplete and therefore could not be analyzed. Out of requests of TDM for adverse effects, lithium levels were above therapeutic range (>1.2 mmol/L) in 17%, subtherapeutic (<0.6 mmol/L) in 23%, and within therapeutic range (0.6-1.2 mmol/L) in 60% cases. Thirty percent of the requisitions for routine monitoring had lithium levels in subtherapeutic range and 7% were above therapeutic range. TDM for lithium is necessary in clinical practice, and this study further confirms the need for TDM, as lithium levels remain below or above the therapeutic range in a substantial number of cases. Regular lithium level monitoring helps in uncovering unsuspected poor compliance and for better clinical management.