An observational nationwide register based cohort study on lamotrigine versus lithium in bipolar disorder.

It is not clear whether the effectiveness of lamotrigine versus lithium differs for patients with bipolar disorder treated in clinical practice. We compared rates of switch to, or add on of, another psychotropic, and rates of psychiatric hospitalization for patients treated with lamotrigine or lithium in clinical practice. Using linkage of nationwide Danish registers we identified 730 patients who received lamotrigine and 3518 patients received lithium subsequent to a diagnosis of bipolar disorder in psychiatric hospital settings during a period from 1995 to 2006. The overall rate of switch to or add on of another psychotropic (the opposite drug of interest (lithium or lamotrigine), antidepressants, antipsychotics or other anticonvulsants than lamotrigine) was increased for lamotrigine compared with lithium (HR = 2.60, 95% CI: 2.23-3.04), regardless of whether the index episode was depressive, manic, mixed or remission. In addition, the overall rate of psychiatric hospitalization was increased for lamotrigine compared with lithium (HR = 1.45, 95% CI: 1.28-1.65), as were the rates for patients with a depressive (HR = 1.31, 95% CI: 1.01-1.70) and patients with a manic (HR = 1.65, 95% CI: 1.31-2.09) index episode. Rates did not differ significantly between the drugs for patients with a mixed index episode and for patients in remission. It is concluded that in daily clinical practice, treatment with lithium is in general superior to treatment with lamotrigine.