A Cochrane review included one study with a total of 36 subjects. Clioquinol (PBT1) was compared with placebo. There was no statistically significant difference in cognition (as measured on the ADAS-Cog scale) between active treatment and placebo groups at 36 weeks. One subject in the active treatment group developed neurological symptoms (impaired visual acuity and colour vision) which resolved on cessation of treatment and was thought to be possibly attributable to the drug.
Comment: The quality of evidence is downgraded by limitations in study quality (inadequate or unclear allocation concealment), by imprecise results (few patients) and by indirectness (differences in studied patients).