Two top Saudi Arabian showjumpers will miss the London Olympics after being hit with eight-month bans.
Horses ridden by Khaled Al Eid and Abdullah Al Sharbatly tested positive for phenylbutazone and oxyphenbutazone at competitions in Saudi Arabia and the United Arab Emirates.
The sport's governing body - the Federation Equestre International - announced findings of an FEI tribunal into the cases.
Al Eid's horse Vanhoeve tested positive at an event last December, while Al Sharbatly's Lobster 43 delivered an adverse result in February.
Controlled medication substances, as in these cases, are prohibited in competition but permitted for treatment use outside competition.
Punishment can range from a warning to a maximum two-year suspension.
Phenylbutazone is a non-steroidal anti-inflammatory drug (NSAID) predominantly used as an anti-inflammatory and analgesic for musculo-skeletal conditions.
Oxyphenbutazone, a metabolite of phenylbutazone, is also an NSAID with anti-inflammatory and analgesic effects. Both substances are classified as controlled medication substances under the FEI equine prohibited substance list.
The three-man FEI tribunal ruled that Al Eid "failed to prove that ingestion by means of exposure to a contaminated stable environment was the likely source of the prohibited substances found in the horse's system".
"The tribunal found that Abdullah Waleed (Al) Sharbatly, failed to establish how the prohibited substances entered the horse's system."
Both riders have until June 22 to lodge any appeal with the Court of Arbitration for Sport in Lausanne.
The punishments are backdated to start in February.A spokesman for Saudi Equestrian confirmed an appeal would be lodged following the verdict.
"Saudi Equestrian is deeply disappointed with the findings of the FEI tribunal that has resulted in an eight-month ban for both Khaled Abdulaziz Al Eid and Abdullah Waleed Sharbatly, and will be appealing the decision through the Court of Arbitration of Sport in Lausanne immediately," he said.
"We would like to categorically state that neither phenylbutazone nor oxyphenbutazone, commonly known as bute, have ever been prescribed by the Saudi Equestrian team vet.
"Saudi Equestrian is a strong advocate of the FEI's Clean Sport campaign, and the welfare of the horse is central to the entire team's ethos."