Murder mom Susan Smith has gotten hooked on drugs in prison and has formed a drug ring of fellow inmates to feed her voracious appetite for narcotics.

“Susan is a drug queen,” reveals ex-con Debra Bost, who was released Feb. 1 from Smith’s prison.

“Other prisoners bring her medications that they take or steal, and Susan pays top dollar from her prison account to get all the drugs she needs,” Bost told The ENQUIRER.

Convicted of writing bad checks, Bost served two and a half years at South Carolina’s Leath Correctional Institution, where Smith is serving a life term for the horrendous 1994 crime that stunned the nation.

The cold-blooded mom locked her sons Michael, 3, and 14-month-old Alex, in her car and sent them to a watery grave in a lake.

“When I got to prison, Susan was in a different building,” said Bost. “But word gets around. I heard that when she would go to bed, the other ladies would make crying sounds like a child, and shout things like, ‘Please Mommy, get me out. I’m wet. I’m cold.’

“Susan had a breakdown from all the teasing and also because her lesbian lover, a prisoner called Big Daddy, got released. So they moved her to my building and put her on psychiatric medications.”

Susan liked the drugs so much, she wanted more and more, said Bost. “She let it be known she could pay for as many pills as the other prisoners could get their hands on. Nutty people send her money all the time because she’s famous, so she’s got more than most prisoners.”

Because she always has funds, Smith can transfer money to other prisoners’ accounts as payment for drugs.

Bost says the notorious mother likes the antidepressant Wellbutrin, the anti-seizure medication Neurontin and the painkiller Parafon Forte, which inmates refer to as “Green Meanies.”

“One inmate got into the pharmacy when there was only one nurse on duty in another room and stole a bag of 120 Neurontin pills,” said Bost. “Susan paid $80 for 40 of them.”

Some prisoners who legitimately receive medications sell them to Susan, said Bost.

“Susan crushes the Wellbutrin pills and snorts them. I saw her with the white powder still stuck on her nose.”

Snorting Wellbutrin gives the user an amphetamine-like high. Smith’s drug appetite is matched by her sexual desires, revealed Bost. The child killer has taken up with an armed robber.

“Susan is proud of a sex technique she taught her. I was sitting outside one day and Susan was describing it, saying, ‘I taught her, and she ain’t doing it with nobody else.’”