Former 400 metres world champion Antonio Pettigrew died in August of an antihistamine overdose, according to a state autopsy report.
The death was ruled a suicide with "diphenhydramine toxicity" as the cause, according to the autopsy and an accompanying investigation report released by the North Carolina Chief Medical Examiner's office.
Pettigrew, 42, was an assistant track and field coach at the University of North Carolina and a 2000 Olympian who was stripped of his 4x400 metres relay gold medal after admitting to doping. He also was the 1991 400 metres world champion.
He was found unresponsive by friends in the back seat of his vehicle in rural central North Carolina on August 10.