A Cochrane review [Abstract] 1 included 22 studies with a total of 1254 subjects with confirmed Huntington's disease. Trials with any symptomatic treatment were included. Nine trials had a cross-over design and 13 were conducted in parallel. Study duration ranged from 2 to 80 weeks. Various pharmacological interventions were studied, mostly anti-dopaminergic drugs (tetrabenazine, sulpiride, tiapride, clozapine, n = 5), glutamate receptor antagonists (amantadine, riluzole, remacemide, ketamine, n = 5) and energy metabolites (ethyl-eicosapentaenoic acid, unsaturated fatty acids, n = 5). The other interventions.were cannabidiol, donepezil, fluoxetine, minocycline, piracetam and trans-dyhidrolisuride. The end-points were control of motor symptoms, specifically chorea, improvement of cognitive function and functional capacity; in eight trials the primary outcome measure was not clearly stated. Only tetrabenazine showed a clear efficacy for the control of chorea using the UHDRS motor scale (3.5 point reduction, 95 % CI: -5.2 to -1.9) but serious adverse events occurred exclusively in the tetrabenazine group. The remaining pharmacological interventions revealed no clear effectiveness over placebo. None of the trials was primarily conducted to study the control of psychiatric symptoms or cognitive decline, having a significant effect on the quality of life of the Huntington's patient.
Comment: The quality of evidence is downgraded by study limitations (inadequate allocation concealment), inconsistency (heterogeneity in interventions and outcomes) and indirectness of evidence (differences between the outcome of interest).
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