Urinary ethyl glucuronide and 5-hydroxytryptophol levels during repeated ethanol ingestion in healthy human subjects

Aims: This study investigated the stability and reproducibility of urinary ethyl glucuronide (EtG) and the 5-hydroxytryptophol (5-HTOL) to 5-hydroxyindole-3-acetic acid (5-HIAA) ratio, both of which are used as biochemical markers of recent alcohol consumption, after single and multiple oral doses of ethanol in healthy human subjects. Methods: Nine females aged 19-27 years drank ethanol (8%, w/v, in juice) or placebo (juice) in random order. The intervention consisted of 0.4 g/kg (22-28 g) of ethanol or placebo twice daily (in the morning and evening) during 8 consecutive days, starting in the evening on day 1. Spot urine samples of the first morning void were collected during the 8-day drinking period and for another 3 days (days 9-11) with no intake of ethanol or placebo. Ethanol, EtG, 5-HTOL and 5-HIAA were determined in the urine samples by headspace GC, LC-MS, GC-MS and HPLC, respectively. Results: The individual results during the drinking period were highly variable, both within and between subjects, ranging from 0-7.3 mmol/l for ethanol, 1.4-71.0 mg/l for EtG, 0.1-4.5 mg/mmol for the EtG/creatinine ratio, and 2-109 nmol/mumol for 5-HTOL/5-HIAA. The placebo group consistently showed negative values for ethanol (<0.1 mmol/l) and 5-HTOL/5-HIAA (<15 nmol/mumol), but two samples were positive for EtG (>0.1 mg/l). In the morning of day 9 (i.e. similar to14-15 h after the last dose), ethanol was no longer measurable in urine and the 5-HTOL/5-HIAA ratio had returned to below the reference value, but detectable levels of EtG (11.3 +/- 6.0 mg/l, mean +/- SD) and the EtG/creatinine ratio (1.0 +/- 0.3 mg/mmol) were found in all samples. Conclusions: The results confirm the increase in urinary EtG and 5-HTOL levels during acute ethanol intake, although the individual values were highly variable both within and between subjects. No significant accumulation of either compound occurred upon multiple-dose administration of 0.8 g/kg (44-57 g) ethanol per day for similar to1 week.