WITHDRAWN: Tacrine for Alzheimer's disease

Area of Science:

• Neuroscience
• Pharmacology
• Clinical Medicine

Background:

• Tacrine was an early Alzheimer's disease (AD) medication, but its efficacy remains debated.
• Controversy stems from inconsistent trial results, methodological issues, and adverse events.
• The drug's limited approval and prescription rates reflect this uncertainty.

Purpose of the Study:

• To critically evaluate the clinical efficacy of tacrine for managing Alzheimer's disease symptoms.
• To synthesize evidence from randomized controlled trials comparing tacrine to placebo.

Main Methods:

• Systematic search of the Cochrane Dementia Group Register of Clinical Trials for relevant studies.
• Inclusion of unconfounded, double-blind, randomized trials of tacrine versus placebo in Alzheimer's type dementia.
• Independent data extraction and meta-analysis using pooled odds ratios and average differences; intention-to-treat data prioritized.

Main Results:

• No clear evidence of tacrine's benefit for overall clinical improvement or behavioral symptoms.
• Minimal, borderline statistically significant improvement in cognitive function on one scale (ADAS-Cog), but not others (MMSE).
• Tacrine significantly increased withdrawal rates due to adverse events, particularly elevated liver enzymes and gastrointestinal issues.

Conclusions:

• Current evidence does not convincingly support tacrine's use for Alzheimer's disease symptoms.
• Methodological limitations and inaccessible data in existing trials hinder definitive conclusions.
• Urgent need for independent meta-analysis of individual patient data from all relevant trials.