A Philadelphia doctor serving life in prison for killing newborns at his abortion clinic has admitted he sold painkiller prescriptions out of his clinic. 

Dr. Kermit Gosnell pleaded guilty Tuesday to federal drug charges after twice walking away from scheduled plea hearings.

Prosecutors said he flooded Philadelphia streets with OxyContin, codeine-laced cough syrup and the antidepressant Xanax, after selling prescriptions to addicts and drug dealers at his street-corner clinic.

Gosnell, 72, is already serving life without parole in the deaths of three babies born alive at his Women's Medical Society in West Philadelphia. 

Gosnell's federal plea Tuesday calls for a guideline sentence of 24 to 30 years, plus $200,000 in forfeited assets. He is set to be sentenced on Oct. 4.