Team Sky's Chris Froome says the last few months have been difficult, after it emerged last year that he had double the allowed level of legal asthma drug salbutamol in his urine.
The information came to light after the British cyclist was tested following the 18th stage of the Vuelta a Espana on September 7.
The 32-year-old, four-time Tour de France winner, also said he had received great support and was now preparing for the challenges ahead.
Speaking after the fifth stage of the Tirreno-Adriatico race, Froome said: "The support has been incredible. It's been a tough-tough period, hasn't been easy for me but I'm getting through it.
"But I'm staying focussed on the goals ahead."
Sunday's stage was won by Briton Adam Yates who burst clear during the final five kilometres, to beat three-time world champion Peter Sagan into second place.