Jockey Ric McMahon has been disqualified for six months after returning a positive test to methylamphetamine and amphetamine.

McMahon was stood down from riding two weeks ago and then asked to front stewards after his `B' sample also tested positive to the substance.

He pleaded guilty under Australian Racing Rule 81 in which a jockey can not return a positive urine sample to a prohibited substance.

While amphetamine can be found in prescription drugs methylamphetmine is found in illegal drugs such as speed, ice, chalk or ecstasy.

It is understood one of the issues McMahon raised was that he had used an illegal drug to keep his weight down.

McMahon's six months disqualification will expire on January 28.

He has five days in which to appeal and can also later ask for his disqualification to be altered to a suspension so he can ride trackwork.

Apprentice Matt McGillivray was disqualified for four months for using ecstasy earlier this year and is eligible to reapply for his licence next month.