A person addicted to heroin went through the following treatment to stop his drug abuse: a doctor gradually replaced his daily heroin dosage with the legal drug methadone.
What kind of treatment is this?

Maintenance therapy

Explanation:

This is a type of maintenance therapy that is used usually at the beginning of the treatment. Methadone is also opioid which means that is addictive but it is not the same as heroin.

Methadone is also bad, but it is safer for patients, it is taken orally, it is not injected as heroin so it cannot lead patients to various diseases such as HIV. Another different and good thing is that there is no need for the crime of stealing when it comes to methadone.

hmmm

true, i think.

i checked and it seems the answer is, true.