Carbamazepine augmentation for schizophrenia: how good is the evidence?

Augmentation strategies in schizophrenia treatment remain an important issue because despite the introduction of several new antipsychotics, many patients remain treatment resistant. The aim of this study was to undertake a systematic review and meta-analysis of the safety and efficacy of one frequently used adjunctive compound: carbamazepine.

Randomized controlled trials comparing carbamazepine (as a sole or as an adjunctive compound) with placebo or no intervention in participants with schizophrenia or schizoaffective disorder were searched for by accessing 7 electronic databases, cross-referencing publications cited in pertinent studies, and contacting drug companies that manufacture carbamazepine.

The identified studies were independently inspected and their quality assessed by 2 reviewers. Because the study results were generally incompletely reported, original patient data were requested from the authors; data were received for 8 of the 10 randomized controlled trials included in the present analysis, allowing for a reanalysis of the primary data. Dichotomous variables were analyzed using the Mantel-Haenszel odds ratio and continuous data were analyzed using standardized mean differences, both specified with 95% confidence intervals.

Ten studies (total N = 283 subjects) were included. Carbamazepine was not effective in preventing relapse in the only randomized controlled trial that compared carbamazepine monotherapy with placebo. Carbamazepine tended to be less effective than perphenazine in the only trial comparing carbamazepine with an antipsychotic. Although there was a trend indicating a benefit from carbamazepine as an adjunct to antipsychotics, this trend did not reach statistical significance.

At present, this augmentation strategy cannot be recommended for routine use. The most promising targets for future trials are patients with excitement, aggression, and schizoaffective disorder bipolar type.