A Cochrane review [Abstract] 1 included 10 studies with a total of 258 subjects. One study was a medium-term study with a duration of 14 weeks but all others were in the 'short-term' category being between one and six weeks long within a single treatment phase. Carbamazepine augmentation was superior compared with antipsychotics alone in terms of overall global improvement, but participant numbers were low (2 RCTs n=38, RR 0.6 CI 0.4 to 0.9, NNT 2 CI 1 to 5). There were no differences for the mental state outcome of 50% reduction in BPRS scores (6 RCTs n=147, RR 0.9 CI 0.7 to 1.1). Less people in the carbamazepine augmentation group had movement disorders than those taking haloperidol alone (1 RCT n=20, RR 0.4 CI 0.1 to 1.0). Adding carbamazepine to antipsychotic treatment was as acceptable as adding placebo (8 RCTs n=182, RR 0.5 CI 0.2 to 1.4). One study comparing carbamazepine with placebo as the sole treatment for schizophrenia was abandoned early due to high relapse rate with 26 out of 31 participants relapsing by three months. No effect of carbamazepine was evident with no difference in relapse between the two groups (1 RCT n=31, RR 4.1 CI 0.8 to 1.5). Another study compared carbamazepine with antipsychotics as the sole treatment for schizophrenia. No differences in terms of mental state were found when comparing 50% reduction in BPRS scores (1 RCT n=38, RR 1.2 CI 0.8 to 1.9). A favourable effect for carbamazepine was found when more people who received the antipsychotic (perphenazine) had parkinsonism (1 RCT n=38, RR 0.03 CI 0.00 to 0.04, NNH 1 CI 0.9 to 1.4). No data were available for the effects of carbamazepine on subgroups of people with schizophrenia and aggressive behaviour, negative symptoms or EEG abnormalities or with schizoaffective disorder.
Comment: The quality of evidence is downgraded by imprecise results (few patients and wide confidence intervals) and by study quality (inadequate follow up).
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