In some medical situations, a doctor or physician might order Methadone for a patient who is experiencing chronic pain or illness. Normally, Methadone is not generally prescribed for moderate or weak levels of pain because there are other, much safer medications that can be used such as Hydrocodone. But in some rare cases a doctor will prescribe Methadone when the pain is severe and it keeps popping back up, even when the patient is using a painkiller. Methadone lasts a long time in the body and therefore is a good choice when the pain is severe and keeps breaking through other medications that have been tried.
This "sticky factor" is a huge part of what makes Methadone so addictive. It is very, very difficult to stop taking Methadone once you are on it. The problem is that the drug is so sticky that it tends to cling to your opiate receptors in your brain for much longer than other opiate painkillers would. This makes for an agonizing and slow withdrawal process.
Keep in mind that treating chronic pain with an opiate is a bit like trying to use alcohol as an anesthetic for surgery. Consider this analogy for a while and you will start to see how painkillers are working in our brain in order to try and treat physical pain. What is actually occurring is that the actual site of the pain is not being treated at all, but instead the opiate drugs are fogging the physical brain so much that the person simply stops being concerned with any pain that their body might be in at the time. Getting to this point when a person is in intense pain means that you have to seriously medicate them to the point of being practically oblivious. Imagine using enough alcohol with a patient to properly prepare them for surgery and you have an idea of just how "out of it" a person can be on Methadone.
People think that Heroin is the worse opiate drug in the world and they think it is the most addictive. In some ways this might actually be the case. But if you look at the severity of cold turkey withdrawal, Methadone is actually worse than Heroin. When coming off of Heroin, anyone can go to a treatment center or drug rehab , stop using the drug immediately, and have medications administered that can control most of the detox symptoms. With Methadone, if people are taking a high enough amount of the drug, then this is really not even possible. The only way to avoid an intense and miserable withdrawal is to slowly ween the addict down in their dosage over time so that they are only taking a minimal amount of Methadone. This is not easy for some addicts to do in itself, especially if they have chronic pain issues that they are dealing with also. In fact, it can be very difficult to get off Methadone, even with this slow weening down process in a person with no chronic pain.