A Cochrane review [Abstract] 1 included 11 studies with a total of 343 patients. No study followed people up for longer than 8 weeks. There was clinically important improvement in TD symptoms after GABA agonist treatment vs. placebo at 6 to 8 weeks follow-up (RR 0.83, CI 0.74 to 0.92; 6 RCTs, n = 258). There was no difference between GABA agonist treatment and placebo for deterioration of TD symptoms (RR 1.90, CI 0.70 to 5.16; 5 RCTs, n = 136). Studies reporting adverse events found a significant effect favouring placebo compared with baclofen, sodium valproate or progabide for dizziness/confusion (RR 4.54, CI 1.14 to 18.11; 3 RCTs, n = 62) and sedation/drowsiness (RR 2.29, CI 1.08 to 4.86; 4 RCTS, n = 144). Studies reporting on akathisia (RR 1.05, CI 0.32 to 3.49; 2 RCTs, n=80), ataxia (RR 3.25, CI 0.36 to 29.73; 2 RCTs, n=95), nausea/vomiting (RR 2.61, CI 0.79 to 8.67; 2 RCTs, n=64), loss of muscle tone (RR 3.00, CI 0.15 to 59.89; 1 RCT, n=10), hypotension (RR 3.04, CI 0.33 to 28.31; 2 RCTs, n=119) found no significant difference between GABA drug and placebo. Evidence on mental state also showed no effect between treatment groups (RR 2.65, CI 0.71 to 9.86; 6 RCTS, n = 121) as did data for leaving the study early (around 10% in both groups, RR 1.47, CI 0.69 to 3.15; 6 RCTS, n = 218). For the outcome of 'no clinically important improvement in tardive dyskinesia' GABA agonist drugs were not better than placebo (RR 0.83 CI 0.6 to 1.1; n = 108). Deterioration in mental state was more likely to occur in people receiving GABA medication (RR 2.47 CI 1.1 to 5.4; n = 95). There is a suggestion of an increase in ataxia for both baclofen and sodium valproate (RR 3.26 CI 0.4 to 30.2; n = 95), and in sedation (RR 2.12 CI 0.8 to 5.4; n = 113) compared with placebo, but this was not significant.
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment), imprecise results (small study size) and indirectness (short follow-up time).
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