Fabio Cannavaro has failed a doping test after taking a medicine containing banned substance cortisone.
Cannavaro, who took the medicine in August, had sought an exemption, claiming he was treating a wasp sting.
However, the Juventus defender's application was missing documentation and, while awaiting a decision, he was subsequently tested.
Juventus have said the medicine was indispensable to "prevent eventual complications, even lethal ones".
The statement on the club's website added: "[We acted] within health procedures and [moral] rules, intervening in an urgent manner following the worsening of the clinical condition following the sting by an insect.
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"The player and the medical staff of Juventus will be at the disposal of the [anti-doping committee] to clarify this issue."
Cannavaro is set to be interviewed by the Italian Olympic Committee's (Coni) anti-doping prosecutor Etorre Torri on Friday.
The 36-year-old, Italy's most capped player and captain during their 2006 World Cup triumph, is currently on international duty as his side aim to seal qualification for the 2010 World Cup in South Africa.
He is expected to return to lead the side against Cyprus next Wednesday.
He will be missing from Saturday's key World Cup qualifier match against the Republic of Ireland due to a prior suspension.
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