Therapeutic drug monitoring of mood stabilizers in Medicaid patients with bipolar disorder.

OBJECTIVE: The authors' goal was to determine the extent and pattern of blood serum monitoring of mood stabilizers in Medicaid patients with bipolar disorder.
METHOD: Data were drawn from a Medicaid medical claims data set from Pittsburgh and the surrounding region. The authors identified bipolar patients using lithium, valproate, and carbamazepine (N = 718) and then examined the patient demographic, diagnostic, and service use variables associated with therapeutic drug monitoring.
RESULTS: A substantial proportion of lithium users (36.5%), valproate users (42.4%), and carbamazepine users (42.2%) with bipolar disorder diagnoses did not receive therapeutic drug level testing during the 12-month study period. Carbamazepine users who were male or in the 30-49-year age range were significantly less likely to be tested for serum drug level. Lithium users who did not receive partial-hospitalization psychiatric services and valproate users who received mental health case management were also less likely to be tested for serum drug level. Over one-half of the lithium users (54.1%) did not receive thyroid function tests, and few (4.2%) received renal function tests. Patients who did receive tests for serum drug level were likely to receive the other recommended tests.
CONCLUSIONS: Many Medicaid patients with bipolar disorder received no therapeutic drug monitoring. Patient sociodemographic characteristics contributed little to explaining this omission, although some types of service utilization were related to rates of serum drug level testing.