Comparing the acute toxicities of co-exposure to cocaine and ethanol versus cocaine alone.

Introduction: Cocaine is commonly consumed with ethanol, which leads to the formation of cocaethylene through transesterification. Cocaethylene is an active metabolite of cocaine with a longer duration of action. Literature on the combined toxicity of cocaine, ethanol, and cocaethylene is conflicting. We aimed to compare the acute toxicities of co-exposure to cocaine and ethanol versus cocaine alone in Hong Kong.

Methods: This was a retrospective study on acute cocaine toxicities reported to the Hong Kong Poison Control Center from 1 January 2010 to 22 January 2023. Cocaine exposure was confirmed by urine immunoassays/laboratory tests and ethanol co-ingestion was confirmed by blood ethanol concentrations. A serious outcome was defined as a National Poison Data System outcome moderate or above. Univariate analyses and multivariable logistic regression were performed to compare the associations of clinical outcomes with and without ethanol, followed by subgroup analyses of cases with complete data.

Results: We analyzed 109 patients (median age 29 years, 71% men, 68% Chinese), of whom 20 had confirmed ethanol co-ingestion (mean blood ethanol concentration 1350 mg/L). Multivariable analysis showed that co-exposure to cocaine and ethanol was associated with a lower risk of serious outcomes (adjusted odds ratio 0.09, 95% confidence interval 0.01-0.77; = 0.03) after adjusting for age, sex, ethnicity, route of cocaine administration, and physical health status. Subgroup analyses showed similar findings.

Conclusions: In contrast to previous studies, we did not identify a higher risk of serious outcomes after co-exposure to cocaine and ethanol compared to cocaine alone in a predominantly Chinese cohort.