Maria Sharapova says she is "determined to fight back" after testing positive for meldonium.
In a Facebook post railing against "distorted and exaggerated" reporting, she denied taking meldonium every day and missing five warnings that the drug was about to be banned.
She also criticised the tennis authorities for making the relevant information "too hard to find".
Russian Sharapova, 28, will be provisionally suspended from 12 March.
The five-time Grand Slam-winner, who faces a ban of up to four years, says she has been taking the drug, which was added to the World Anti-Doping Agency's banned list on 1 January, for health reasons for the past 10 years.