Ethanol Pharmacokinetics and Alcohol-Related Effects after One-Anastomosis Gastric Bypass: A Prospective Before-After Study.

INTRODUCTION: Metabolic-Bariatric surgery is associated with altered ethanol pharmacokinetics and increased alcohol-related risk. While these changes have been described after Roux-en-Y gastric bypass and sleeve gastrectomy, data regarding one-anastomosis gastric bypass (OAGB) have not been reported. This exploratory study evaluated changes in alcohol absorption, elimination, and subjective intoxication following OAGB. METHODS: In this prospective before-after interventional study, adults undergoing OAGB were assessed preoperatively and at 1 and 4 months postoperatively. At each visit, participants ingested 200 mL of red wine (13.5% alcohol by volume; ∼21.3 g ethanol). Breath alcohol concentration (BrAC) was measured at fixed time points over 2 hours using a calibrated breathalyzer. Pharmacokinetic parameters, including maximum concentration (Cmax), time to maximum concentration (Tmax), area under the concentration-time curve (AUC0-inf), and elimination half-life (t1/2), were determined. Subjective alcohol effects were assessed using a standardized symptom questionnaire, and pharmacokinetic-pharmacodynamic relationships were examined. RESULTS: Ten participants (mean age 42 ± 12.8 years; 60% female) were included. Mean Cmax increased from 0.43 ± 0.33 g·L-1 preoperatively to 1.19 ± 0.30 g·L-1 at 1 month and 1.24 ± 0.36 g·L-1 at 4 months postoperatively. AUC0-inf increased from 21.0 ± 15.2 to 71.2 ± 31.5 and 91.2 ± 39.3 g·min·L⁻¹, respectively. Ethanol elimination half-life was prolonged after surgery, and differences remained statistically significant after BMI standardization. Intoxication symptom scores increased postoperatively, and positively correlated with pharmacokinetic parameters, with Cmax having the strongest association. CONCLUSIONS: OAGB alters ethanol pharmacokinetics, leading to higher peak alcohol concentrations, increased systemic exposure, and enhanced subjective alcohol effects. Even modest alcohol intake may potentially lead to high BrAC levels after OAGB, reflecting the need for clinician-led patient education and advice on safer alcohol use after surgery. Given the small sample size, participant attrition, and short postoperative observation period, the study findings should be interpreted with caution.