Background and importance: Patients who use recreational drugs frequently co-ingest ethanol, which is considered a central nervous system (CNS) depressant. The clinical relevance of this in acute toxicity involving other CNS depressants is not well described. Objective: To assess the clinical impact of ethanol co-use in patients presenting to the emergency department (ED) with acute toxicity involving the use of CNS depressant drugs. Design, settings and participants: A retrospective multicentre study using data from the Euro-DEN Plus database from January 2014 to December 2019. Outcomes measure and analysis: Comparison of epidemiologic and clinical characteristics, ED and hospital management of patients with CNS depressant intoxication with or without ethanol co-use. Main results: Although 7644 (17.5%) of the 43 633 presentations were included, ethanol was co-ingested in 3811 (49.9%). In total 53.3% required medical treatment, 14 patients died. Patients with ethanol co-use more frequently presented with a Glasgow Coma Scale (GCS) <=8 (34.1% vs. 22.4%; P < 0.001), vomiting (8.1% vs. 4.6%; P < 0.001), anxiety (12 % vs. 6.4%; P < 0.001), agitation/aggression (22% vs. 14.7%; P < 0.001), seizures (3.8% vs. 2.4%; P < 0.001) and hypotension (7.5% vs. 4.6%; P < 0.001). They more often required ambulance transport (85.5% vs. 76.5%; P < 0.001), medical treatment (57.3% vs. 48.0%; P < 0.001), hospitalization (27.7% vs. 18.9%; P < 0.001), and admission to intensive care (12.2% vs. 4.0%; P < 0.001). Subgroup analysis showed that GCS <=8 was particularly common in patients who combined ethanol with opioids or gamma-hydroxybutyrate (GHB)/gamma-butyrolactone (GBL). Conclusion: Co-use of ethanol with CNS-depressant drugs appears to increase the risk of adverse effects and is associated with a higher need for medical treatment, especially when ethanol is combined with opioids or GHB/GBL.