Irish showjumper Jessica Kurten is to contest a positive B test taken from her mount Castle Forbes Maike.
Ireland's Jessica Kurten denies ever doping her mount
A statement from the International Equestrian Federation (FEI) confirmed the test result, which was taken while competing at La Baule in France in May.
The horse tested for etoricoxib which is a non-steroidal, anti-inflammatory medical class A drug.
Kurten, though, has refused the chance to accept a fine and an administrative fee amounting to just over 750 euros.
Following the original positive A sample, the Culleybackey rider was given the option of paying a fine of around 300 euros and return her first place 22,000 euros prize-money won at the French Grand Prix.
But Kurten believes paying the fine would be an acceptance of doing something wrong.