Impact of Water-Induced Diuresis on Excretion Profiles of Ethanol, Urinary Creatinine, and Urinary Osmolality

This article reports the impact of diuresis on urinary excretion of ethanol in seven healthy volunteers who drank 1000 mL of export beer (44 g ethanol) in 30 min and, 120 min later, ingested 500 or 1000 mL of water within 5 min. Urine was voided before drinking started and every 30-60 min for 360 min after the start of drinking. The concentration of ethanol in urine (UAC) was determined by headspace gas chromatography, the creatinine content was determined by Jaffe's method, and osmolality was measured by freezing point depression. Maximum diuresis coincided with the peak UAC and was reached 60-90 min after the end of drinking. The urinary creatinine and osmolality dropped appreciably after drinking beer, and the lowest values coincided with peak diuresis. Creatinine was < 0.2 g/L in 22% of urine specimens, and osmolality was < 200 mOsm/kg in 31% of specimens. Production of urine decreased as UAC entered the postabsorptive phase but increased again after the subjects drank water 120 min after alcohol consumption. The amount of ethanol recovered in urine was 681 mg (standard deviation [SD] 203 mg) corresponding to 1.5% (SD 0.46%) of the dose administered. The concentrations of ethanol in successive voids during the postabsorptive phase were not influenced after subjects drank 500 or 1000 mL of water although diuresis increased and urinary creatinine and osmolality decreased. Measuring UAC provides a reliable way to monitor recent drinking, and unlike the analysis of illicit drugs in urine, the concentrations of ethanol are not influenced by diuresis.