Egyptian boxer Fadel Showban on has been sent home from Sydney in disgrace after Olympic officials discovered he had failed a drugs test before the Games.

Showban fought in the 67kg class on the first day of the boxing at Darling Harbour, hammered on points by American Donte Craig of the United States, before officials learned about his test.

According to the Amateur International Boxing Federation, Showban had claimed he had taken a diuretic along with other drugs to aid his recovery from a broken leg.

Diuretics, although helping one to lose weight, also serve as a masking agent for performance-enhancing drugs.