Marin Cilic has been suspended for nine months and will miss next year's Australian Open after he tested positive for a banned stimulant, the International Tennis Federation has announced.
The Croatian's doping violation came when he tested positive for nikethamide - a stimulant - at the BMW Open in Munich in May.
The 24-year-old's ban was backdated to May 1, the date on which he provided the sample, to end at midnight on January 31, 2014.
A statement from the ITF read: "The Independent Tribunal found that Mr Cilic ingested the nikethamide inadvertently as a result of taking the Coramine glucose tablets, and did not intend to enhance his performance in doing so, and that he therefore met the preconditions of Article 10.4 of the Programme, which entitles him to a reduction of the Period of Ineligibility for Specified Substance based on an assessment of his fault."
As well as the ban "it was also determined that Mr Cilic's results at the 2013 BMW Open event should be disqualified, with resulting forfeiture of the ranking points and prize money that he won at those events.
"Mr Cilic's results subsequent to the BMW Open, up to the time that he accepted a voluntary provisional suspension are also disqualified, and the ranking points and prize money forfeited. A fully-reasoned decision will follow in due course."
The sample in question was sent to the WADA-accredited laboratory in Montreal, Canada for analysis, where it was found to contain nikethamide, a prohibited substance under section S6 (Stimulants) of the 2013 WADA List of Prohibited Substances and Prohibited Methods, and therefore also prohibited under the Tennis Anti-Doping Programme (the "Programme").
Cilic was subsequently charged over the doping violation under Article 2.1 although he argued the banned substance was in his system after taking Coramine glucose tablets that had been purchased for him from a pharmacy.
Following the BMW Open, Cilic was knocked out of the French Open in the third round by Viktor Troicki, who coincidentally was banned in July for 18 months for failing to provide a blood sample at the Monte Carlo Masters in April.
He then reached the final at Queen's where he lost to Andy Murray before withdrawing from Wimbledon, where he was seeded 10th, prior to his second-round match against Kenny de Schepper with a knee injury.
Cilic will miss the Australian Open while serving out the latter stages of his ban.