Graeme McDowell has been suspended by LIV Golf for one tournament for violating the circuit’s anti-doping policy.
The Saudi-funded series said, external the 45-year-old used “a decongestant medicine that included a banned substance”.
The offence by the Northern Irishman occurred during LIV Golf Nashville in June and he has also been fined 125,000 US dollars (£98,000).
“Ahead of LIV Nashville, I was struggling with severe congestion that was affecting my sleep,” said McDowell, who won the US Open in 2010.
“In an effort to manage it, I used a generic nasal decongestant without realising it might be on the banned list.
“As a professional golfer, I understand the importance of checking all medications and the option to apply for a Therapeutic Use Exemption (TUE).
“Unfortunately, I did not think to do this due to the over-the-counter nature of this medicine and I deeply regret the oversight. I fully accept the sanctions imposed by LIV.”
The results of McDowell and his team from LIV Nashville will be disqualified following his suspension.
He will miss the next event in the series, which starts in West Virginia on 16 August, and can return for the Chicago tournament in September.
“I’m proud of my 22-year career and the way I’ve conducted myself through it,” added McDowell.
“Now, I’m focused on moving forward and getting back on the golf course. I look forward to seeing everyone at LIV Chicago.”