Metabolic alkalosis with hypertonic dehydration in a patient with diarrhoea and magnesium oxide ingestion.

An eight-week-old infant with diarrhoea and dehydration became markedly alkalotic after administration of magnesium oxide powder. The literature does not substantiate the premise that significant magnesium deficiency may occur during acute gastroenteritis in an otherwise healthy infant. Physicians should be warned about this form of therapy as a possible cause of metabolic alkalosis. The possibility of congenital alkalosis with diarrhoea should be considered in differential diagnosis.