Kenyan marathon runner Felix Kirwa has been suspended from competition for nine months after testing positive for the banned substance strychnine.
The 2016 Singapore Marathon winner - banned until 14 November - said he had taken herbal medicines which included the stimulant.
He has been stripped of his second place at the 2018 Singapore Marathon.
Around 50 Kenyan athletes have been sanctioned for doping violations in the past five years.
Three-time world 1500m and 2008 Olympic champion Asbel Kiprop received a four-year ban in April after failing a doping test in November 2017, while 2016 Olympic marathon champion Jemima Sumgong and former Boston and Chicago Marathon winner Rita Jeptoo have also been handed suspensions.