Does effect size in naltrexone trials for alcohol dependence differ for single-site vs. multi-center studies?

Area of Science:

• Pharmacology
• Clinical Trials
• Addiction Medicine

Background:

• Naltrexone, an opioid antagonist, has demonstrated efficacy in treating alcohol dependence.
• Recent clinical trials increasingly utilize multi-center designs for broader generalizability and enhanced statistical power.
• This study investigates the hypothesis that multi-center designs may reduce observed effect sizes due to increased variability.

Purpose of the Study:

• To compare the effect sizes of naltrexone's efficacy in alcohol dependence treatment between multi-center and single-site clinical trial designs.
• To determine if multi-center trials yield different effect sizes compared to single-site trials.

Main Methods:

• A meta-analysis was conducted on data from 19 placebo-controlled trials of naltrexone.
• Trials were categorized into 7 multi-center and 12 single-site studies.
• Effect sizes were compared for two primary outcomes: percentage of days drinking and percentage of subjects relapsing to heavy drinking.

Main Results:

• Multi-center studies showed a nonsignificantly smaller effect on the percentage of days drinking (Cohen's d = 0.20) compared to single-site studies (d = 0.33).
• Multi-center studies demonstrated a significantly smaller effect on the percentage of subjects relapsing to heavy drinking (Cohen's d = 0.17) versus single-site studies (d = 0.41; p = 0.014).
• Earlier studies exhibited larger effect sizes than more recent studies.

Conclusions:

• The reduced effect size in multi-center studies may be attributed to random error stemming from site heterogeneity.
• Disentangling the impact of study type and publication year on effect size was not conclusive due to the recency of multi-center studies.
• Further research into factors moderating effect size is crucial for advancing medications for alcohol dependence treatment.