Lamotrigine for schizophrenia

Treating the 20-30% of people with schizophrenia whose symptoms are resistant to treatment can be problematic. Adding lamotrigine to ongoing antipsychotic treatment has shown to be of benefit in preliminary studies.

To evaluate the effects of adjuvant lamotrigine for people with schizophrenia and schizophrenia-like psychoses.

We searched the Cochrane Schizophrenia Group's Register (February 2006) and inspected references of all identified studies for further trials. We contacted relevant authors of trials for additional information.

We included all clinical randomised trials comparing lamotrigine with placebo or other antipsychotic augmentation strategies.

We extracted data independently. For homogenous dichotomous data we calculated random effects relative risk (RR), 95% confidence intervals (CI) and, where appropriate, numbers needed to treat (NNT) on an intention-to-treat basis. For continuous data, we calculated weighted mean differences (WMD).

We found five relevant trials (total n=537), but no usable data on service outcomes, general functioning, behaviour, engagement with services, satisfaction with treatment or economic outcomes. Overall, reporting of data was poor. Those data we were able to use suggested that equal proportions of people allocated lamotrigine or placebo had no global response (n=208, 1 RCT, RR 1.06 CI 0.73 to 1.54). There was no significant difference between groups in the proportions of people whose mental state did not improve (n=297, 3 RCT, RR 1.26 CI 0.81 to 1.97). There was, however, a significant reduction in the PANSS total scores (n=67, 2 RCT, WMD -16.88 CI -8.57 to -25.18, p=0.0001), positive symptom sub-scale scores (n=65, 2 RCTs, WMD -5.10 CI -8.86 to -1.34) and negative symptom sub-scale scores (n=67, 2 RCTs, WMD -5.25, CI -7.07 to -3.43). Most cognitive measures showed no differences (n=329, 2 RCTs, RR not attaining BACS composite score of 0.5 1.10 CI 0.59 to 2.04). The proportion of participants leaving studies was about 25% at 12 weeks (n=537, 5 RCTs, RR 0.96 CI 0.71 to 1.29). The lamotrigine group did experience the outcome of any adverse effects significantly more frequent than people allocated placebo (n=429, 2 RCTs, RR 1.19 CI 1.02 to 1.38, NNH 10 CI 5 to 90). Among the many effects listed, only nausea was found to be significantly more (9%) in the lamotrigine group compared with placebo (n=465, 3 RCTs, RR 2.26 CI 1.05 to 4.88).

Evidence for use of lamotrigine as an adjuvant for people with schizophrenia is not robust and large well-designed, conducted and reported real-world randomised trials are needed to determine its place in everyday clinical practice.