Frankie Dettori faces an inquiry in France after the jockey gave a "positive test" at Longchamp racecourse in September.
Dettori's solicitor Christopher Stewart-Moore said in a statement: "On behalf of Frankie Dettori I can confirm that, as a consequence of a positive test at Longchamp on September 16 2012, he will be the subject of an inquiry by the Medical Committee of France Galop next week.
"In compliance with, and out of respect for, the regulations of France Galop, he will not be commenting further until the France Galop procedures have been completed."
Dettori had four rides at Longchamp on 16 September, a day of major trials for the Prix de l'Arc de Triomphe meeting the following month.
Dettori after he rode in his last Emirates Melbourne Cup at Flemington Racecourse last week
The Italian partnered Marco Botti's Joshua Tree to finish third in the Qatar Prix Foy, while the John Hammond-trained Sarah Lynx trailed home last in the Prix Vermeille.
He was then beaten just a head into second on Godolphin's Farhh in the Prix du Moulin and was third for his former employers on Willing Foe in the Prix Gladiateur.
France Galop are yet to comment and have not done so in previous similar cases prior to a hearing.
Dettori's 18-year association with Godolphin ended last month, with the Italian jockey planning to ride as a freelance in 2013.