OBJECTIVES : This study was aim to assess the utilization, Indication and direct cost incurred for Therapeutic drug monitoring [TDM] of mood stabilizers in a university hospital.

METHODS : This retrospective, study was carried in a university teaching hospital in Dammam Saudi Arabia. All the data were collected from an electronic medical health record QuadraMed". Patients were included in the study if they had a mood stabilizer serum level drawn between Jan 2017 to Dec 2018. Patient who are withdrawn the treatment from the study site or lost follow up or change the diagnosis were excluded.

RESULTS : Total of 200 patients received 242 mood stabilizers. Gender distribution was almost equal in the study population [male (52%) Vs female (48 %)]. Approximately one half (42%) of the patients were Bipolar type 1. Valproic acid (n=139 57.9%), lithium [n=54 (22.3%)] were the popular mood stabilizers. Greatest number (80%) of the bipolar patients were managed with single mood stabilizers. A total of 613 TDM ordered for the 200 patients, average of number of 3 [ range 1-39).Validation of the therapeutic level (n=140), lack of clinical response [n=51] and change in the dose [n=34] are the documented reasons for TDM. Totally $ 35,432.8 spend over the period of one year for the TDM of mood stabilizers in a single center in Saudi Arabia. Cost of TDM per patient per year was $177. 16

CONCLUSIONS : TDM plays an important role in the development of safe and effective therapeutic medications and individualization of these medications. The average cost of TDM in our study was 177.165 $. More extensive study on a larger sample size in the prospective basis is required to find out the rationality of TDM orders and development of the polices also asses the economic burden of TDM on patient, provider and health care system.