Lamotrigine as add-on therapy in schizophrenia: results of 2 placebo-controlled trials.

OBJECTIVE

: Lamotrigine previously was found to attenuate ketamine-induced behavioral changes and, in 2 placebo-controlled trials, to improve psychosis when added to antipsychotic medication. We sought to evaluate the potential role of lamotrigine augmentation in schizophrenia patients resistant to atypical antipsychotic medication.

METHODS

: Two multicenter, randomized, double-blind, 12-week, parallel-group trials were conducted to compare flexibly dosed lamotrigine (100-400 mg/d) with placebo as add-on treatment in schizophrenia patients with stable, residual psychotic symptoms. The primary end point was changed in Positive and Negative Syndrome Scale total score at week 12.

RESULTS

: Two hundred seventeen patients were enrolled in study 1 and 212 in study 2; completion rates in the intent-to-treat samples were 71% and 74%, respectively, and did not differ between treatment groups. Overall, mean Positive and Negative Syndrome Scale total scores improved in both studies and did not differ between treatment groups. In study 1, the Scale for Assessment of Negative Symptoms total score and Clinical Global Impression improved more with placebo than with lamotrigine; in study 2, the cognitive composite score improved more with lamotrigine than with placebo.

CONCLUSIONS

: Results from these 2 studies do not support the use of lamotrigine as an adjunct to atypical antipsychotics in patients with refractory psychosis. It is unclear why positive results from previous lamotrigine trials were not replicated. The positive effect of lamotrigine on cognition in one trial, while of uncertain significance, may merit further study.