What is the best treatment for narcotic abuse?

Best. Best is to participate in medically supervised detox program. This will increase success and make sure stay safe.
Inpatient treatment. Inpatient treatment with management of withdrawal symptoms and psychotherapy to address causes driving addiction/abuse.
Taper down the dose. The best advice is to taper the drug down slowly over several weeks, then stop using the drug altogether.
Support. Once you detox and are clean, you need to join a support group. Narcotics anonymous and celebrate recovery are two excellent organizations that help people deal with narcotic addiction. I would suggest making arrangements to join a group as you are planning your entry into detox. They might be able to visit you in the detox center and help with your transition to home as well.