KNOX COUNTY, Tenn. — A drug called Vivitrol is being marketed to inmates in the Knox County Jail as a shot to turn their life around. 

Many people haven't even heard of it before. 

RELATED: 10Investigates: Knox County Jail Vivitrol Program

What is Vivitrol?

When used as part of a treatment plan that includes counseling, Vivitrol can help prevent relapse to opioid dependence after detox.

That's the one caveat: Patients must detox before starting the treatment.

Before starting Vivitrol, you must be opioid-free for a minimum of seven to14 days to avoid sudden opioid withdrawal. 

RELATED: Vivitrol treatment program starts in Knox County

How does Vivitrol work?

Vivitrol is an antagonist or blocking medication. 

Antagonists attach to opioid receptors but do not cause the release of dopamine. They are non-addictive and do not lead to physical dependence. Antagonists create a barrier that blocks opioid molecules from attaching to opioid receptors.

According to its website, Vivitrol blocks opioid receptors in the brain for one month at a time, helping patients to prevent relapse to opioid dependence, following detox, while they focus on counseling.