Lindsay Lohan is to be randomly tested for alcohol and drugs until August 2011.

After being sentenced to 90 days in prison and a further three months in an inpatient rehab facility for violating her probation for a DUI arrest in 2007, the Mean Girls star will now have to stay sober and clean for over 12 months on the orders of Judge Marsha Revel.

She will, however, be permitted to take five prescription medications while on probation. These are Nexium for heartburn, antidepressants Zoloft and Trazodone, Adderall for Attention Deficit Disorder (ADD) and painkiller Dilaudid for "dental pain". Based on her probation report released by the Los Angeles court system on Wednesday, Lindsay "has been on the same prescription medication for as long as she can remember. She has provided medical proof for her prescription drugs".

The report also indicates the actress had twice tested positive for amphetamines and opiates in previous drug tests as a result of Adderall and Dilaudid.

The 24-year old star has to surrender herself to authorities on July 20 to begin her sentence.

Steve Whitmore of the Los Angeles County Sheriff's Office said, "She's getting a cell by herself. She will be separated from the general population. She will be in a pod with other inmates in the same classification."