Irish rider Denis Lynch, whose horse Lantinus 3 failed a drugs test at the Beijing Olympics, was on Friday banned for three months, the International Equestrian Federation announced.
Lynch, whose ban was backdated to August 21, was also fined 1,750 Swiss francs and ordered to pay 2,000 Swiss francs towards legal costs.
Five horses failed dope tests at the Beijing Games where the equestrian competition was staged in Hong Kong.
Other horses failing test were Chupa Chup, ridden by Brazil's Bernardo Alves, Coster, the mount of Christian Ahlmann of Germany, Camiro, under Norway's Tony Andre Hansen, and Rufus, ridden by Brazil's Rodrigo Pessoa.
Pessoa, the 2004 Olympic champion, had already been banned for four and a half months.