Croatian Marin Cilic has been banned for nine months after testing positive for the stimulant nikethamide, the International Tennis Federation (ITF) said on Monday.
In a statement the ITF said Cilic had "ingested the nikethamide inadvertently as a result of taking Coramine glucose tablets, and did not intend to enhance his performance in doing so".
The suspension has been backdated to May 1, allowing Cilic to return to the circuit on Jan. 31 next year. Cilic, 24, has not played since withdrawing from his second-round match at Wimbledon in June.
(Reporting by John Mehaffey, editing by Ed Osmond)