Gamma-aminobutyric acid agonists for neuroleptic-induced tardive dyskinesia

Abstract

Background: Chronic antipsychotic drug treatment may cause tardive dyskinesia (TD), a long-term movement disorder. The gamma-aminobutyric acid (GABA) agonist drugs have been trialed as a treatment for TD, but these drugs have intense sedative properties and may exacerbate psychotic symptoms.

Objectives: To determine the effects of GABA agonist drugs (baclofen, gamma-vinyl-GABA, gamma-acetylenic-GABA, progabide, muscimol, sodium valproate and tetrahydroisoxazolopyridine (THIP)) for people with neuroleptic-induced tardive dyskinesia (TD) and schizophrenia or other chronic mental illnesses.

Search strategy: Electronic searches of Biological Abstracts (1982-2000), The Cochrane Library (Issue 4, 2000), Cochrane Schizophrenia Group's Register of Trials (2000), EMBASE (1980-2000), LILACS (1982-2000), MEDLINE (1966-2000), PsycLIT (1974-2000), and SCISEARCH were undertaken. References of all identified studies were searched for further trial citations. First authors of each included trial were contacted.

Selection criteria: The inclusion criteria for all relevant randomised studies were that they should focus on people with schizophrenia or other chronic mental illnesses, with neuroleptic-induced TD and compare the use of non-benzodiazepine GABA agonist drugs to placebo or no intervention.

Data collection and analysis: The reviewers extracted the data independently and the relative risk (RR) and its 95% confidence interval (CI) or the weighted mean difference with 95% CI were estimated. The reviewers assumed that people who dropped out had no improvement.

Main results: Eight small, short, poorly reported studies were included. For the outcome of 'no clinically important improvement in tardive dyskinesia' GABA agonist drugs were not clearly better than placebo (n=108, RR 0.83 CI 0.6 to 1.1). Deterioration in mental state was more likely to occur for people receiving GABA medication (n=95, RR 2.55 CI 1.17 to 5.59), but this effect was influenced by the decision to assign a negative outcome to those who dropped out before the end of the study. A greater proportion of people allocated GABA medication may fail to complete the trial compared with those allocated placebo (20% versus 9%) but, this difference was not statistically significant (n=136, RR 1.99 CI 0.84 to 4.68). There is a suggestion of an increase in ataxia for both baclofen and sodium valproate (n=95, RR 3.26 CI 0.4 to 30), and in sedation (n=113, RR 2.12 CI 0.8 to 5.4) compared with placebo. Withdrawal of THIP may cause seizures.

Reviewer's conclusions: Currently, evidence of effect of baclofen, progabide, sodium valproate, or THIP for people with neuroleptic-induced TD is inconclusive and unconvincing. Any possible benefits are likely to be outweighed by the adverse effects associated with the use of these drugs.