A Cochrane review included 4 studies with a total of 75 patients. Three of the studies were of medium duration (more than 6 weeks to up to 6 months). Using benzodiazepines as an adjunctive treatment did not result in any clear changes for tardive dyskinesia regarding medium term outcomes. RR for not improved to a clinically important extent: 1.12 (95%CI 0.60 to 2.19; 2 RCTs, n=32) and RR for deterioration: 1.48 (CI 0.22 to 9.82; 2 RCTs, n=30). Adverse effects were not reported. All 10 patients on benzodiazepines experienced adverse events compared with 7/11 on phenobarbital (RR 1.53, 95% CI 0.97 to 2.41; 1 RCT, n=21). There was no clear difference in the incidence of patients leaving the study early for benzodiazepines vs. placebo (RR 2.73, 95% CI 0.15 to 48.04; 3 RCTs, n=56).
Comment: The quality of evidence is downgraded by study quality (inadequate or unclear allocation concealment) and by imprecise results (few patients and wide confidence intervals).