Jamaican sprinter Steve Mullings has been left facing a lifetime suspension after testing positive for the banned substance furosemide.
The 28-year-old was previously banned for two years in 2004 for excessive testosterone levels.
"What can I do? I'm going to go in front of the panel and say I never took the drug. But I don't have the proof to say, 'OK, it was vitamins'," said Mullings.
"I've already gone through all my vitamins and there's nothing in there."
The Jamaican Athletics Association last week announced that Mullings would not be part of their squad for the World Athletics Championships in South Korea later this month.
