summary
The effect of ethanol on magnesium excretion was studied in three normal subjects. It was found that the ingestion of 2 ml ethanol/kg body weight produced a marked immediate increase in urinary magnesium excretion, but there was no significant effect on overall magnesium balance when this amount was taken daily for eight days.
LINK - http://www.ncbi.nlm.nih.gov/pmc/articles/PMC474024/