George Michael, who has pleaded guilty to driving while unfit, had several drugs in his system when he was arrested, a court heard Wednesday.

Tests showed the 43-year-old singer had taken a therapeutic quantity of an antidepressant as well as gamma-hydroxybutyrate, or GHB, Prosecutor Andrew Torrington told Brent Magistrates' Court in London.

GHB is often called the "date-rape drug" because it leaves people groggy and powerless.

Michael, who wasn't in court Wednesday, pleaded guilty May 8 to driving while unfit due to drugs. He said his condition was caused by "tiredness and prescribed drugs."

The former Wham! singer, whose real name is George Panayiotou, was arrested in the early hours of Oct. 2 after police responded to complaints that a car was blocking an intersection in North London. Police said Michael was found slumped over the wheel of the car.

His lawyer, Michael Grieve, told the court a prescription sleeping drug was the most likely explanation for Michael's condition.

Michael said in a TV interview earlier this month that he is addicted to prescription drugs and believes the world would be a better place if more people smoked marijuana.

He blamed his erratic behavior to an attention-seeking and "self-destructive" impulse brought on by the death of his mother a decade ago.

The case was adjourned until June 8 for sentencing, the day before Michael performs at Wembley Stadium as part of his European tour.