If you came to methadone because you were addicted to an opiate like heroin, you might have an addiction to the process of shooting drugs, in addition to the addiction to the drugs themselves. For example, a study in the journal Drug and Alcohol Review found that 47 percent of people who shot methadone syrup did so because they had a needle fixation. The idea of heating up the drug, tying the vein and injecting the drug was a process they were addicted to, and had trouble overcoming without help.

Medications that are meant to be swallowed often contain time-release properties, meaning that a tiny amount of the drug becomes active at a time. This allows people to take the drug and feel the effects of the drug over a long period of time. If you shoot time-release methadone, you’ll get the entire impact of the drug all at once. Even a dose you might take orally with no issues could cause an overdose if you inject it, simply because you’ll have the full impact hitting your body at the exact same time. Death can quickly follow a methadone overdose.