A synthetic opiate intended to replace opiate based prescriptions or street drugs, so that an individual can be slowly weaned off and avoid withdrawal symptoms.
Often used as a fix between fixes. Its not uncommon for an addict to be on methadone and still using they're drug of choice.

The doctor put me on methadone because I'm having trouble getting of my meds for my back.

I don't have any cash until my pogey comes in, so I'm going to go get my methadone drink.

A potent synthetic narcotic drug that is less addictive than morphine or heroin and is used as a substitute for these drugs in addiction treatment programs.

Bob is trying to stop shooting heroin by going to the methadone clinic.

a potent opioid based narcotic used to treat moderate to severe pain;not to be injected,however,used to treat people who are withdrawing from other narcotics(Heroin,Dilaudid ,Percocet ect...)

Stans doctor prescribed him Methadone when all other options had failed to control his Pain.

Martha checked into the Methasdone clinic to wean herself off of Heroin.

Methadone is a strong synthetic drug, first made back in world war 2, to help the germans with pain medication as they had a shortage of morphine.
Just to clear up a couple of misconceptions, no doctor is going to prescribe anyone 120 tablets to take in one day as one person stated here. That confusion probably comes from how methadone is prescribed. When methadone is prescribed for pain it is usually prescribed in 5 or 10 mg dose tablets, and are told to take 1 or 2 as need for pain every 4 to 8 hours.
For those on methadone maintence programs to stay off of other narcotics then the patient is prescribed usually somewhere between 80 and 120 mgs in a methadone syrup, that is taken at once and repeated daily. Obviously when a patient first starts they start at between 15 to 30 mgs per day, and increased until they are not craving for the narcotic of there choice anymore. Its probably the difference in how methadone is taken that has caused all the methadone overdose deaths of late. If you have never taken pain medications b4, never take methadone and never take an amount that someone on a methadone maintenance program is on, as that will kill anyone who is not use to those type of doses. After all, even people who get on those programs are even started at between 15 to 30 mgs and worked there way up. Methadone works great for those who use it right, but use it wrong, and it can be a monster that is much more potent. Use methadone right and it will work for you.
Also if you ask anyone on methadone who has tried to come off, they will tell you that it is one of the hardest drugs to withdraw from, with some symptoms lasting months. Percocet and percodan and morphine are much easier to kick then methadone.

John and Sally go down to the methadone clinic to get their daily dose.

A synthetic narcotic drug similar to morphine but less habit-forming; used in treating heroin addiction

A brief relationship or hookup used to get over a serious relationship.

Mike: Are you going to call that girl you hooked up with last night?

Dave:Nah, i just needed some methadone to get over Nancy

Its also used to treat extreme pain, usually in Cancer patients. Methadone is usually prescribed after other narcotic agents are proven to be innafective. Its usually prescribed in large doses, usually 120 pills to be taken 4 times a day.

Oxcontin didn't work for Mr. Jones, so his doctor prescribed Methadone.